Bank of Questions - Electricity

KHALID YOUSEF AL HINDI @ELECTRICITY QUESTIONS
Question1:
Three identical resistors are connected across a potential difference V so that one of them is
in parallel with the other two which are connected in series. The power dissipated through the
first one, compared to the power dissipated by each of the other two, is approximately
a) the same
b) half as much
c) twice as much
d) four times as much
(Total 1 mark)
Question2:
A circuit is set up as shown in the diagram.
When the switch is closed, the potential difference across the 20 Ω resistor would
a) equal the potential difference across the 10 Ω resistor
b) be twice the potential difference across the 10 Ω resistor
c) equal the potential difference across the 40 Ω resistor
d) be half the potential difference across the 40 Ω resistor
(Total 1 mark)
Question3:
How much electrical energy is required to move 4.00 mC of charge through a potential
difference of 36.0 V?
a) 1.11 × 10 –4J
b) 0.144 J
c) 144 J
d) 9000 J
(Total 1 mark)
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Question 5:
Which of the following graphs gives the current-potential difference characteristic of an NTC
thermistor?
Question 14:
The graph shows how the current in a 9 V filament lamp varies during one second after it
has been turned on.
a) A student wishes to carry out an experiment to verify these results. Explain why using a
sensor and computer is a sensible option and suggest a suitable sampling rate
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b) Explain the shape of the graph and why the filament is more likely to fail when being
switched on rather than at other times
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(Total 6 marks)
Question 19:
A group of students is discussing why the resistance of the metal filament of a lamp and the
resistance of an NTC thermistor respond differently to changes in temperature. One student
says that the increased vibrations of the atoms affect the conduction process. Another student
says that as the temperature increases more electrons can break free of the atoms and take
part in conduction. Both students are correct. Explain how these two effects apply to the lamp
and the thermistor
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Question 22:
A student sets up the following circuit to measure the internal resistance of a cell
a) What is wrong with his circuit diagram?

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b) Using the correct circuit the student obtains the following results.
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(i) On the grid below, plot these results and draw the line of best fit through your points
(ii) Use your graph to determine the e.m.f. of the cell.

e.m.f. = ......................................... (1)
(iii) Use your graph to determine the internal resistance of the cell.
Internal resistance = ................... (2)
c) The experiment is repeated with two such cells connected in series. How does the graph
differ?
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(Total 9 marks)
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Question 23:
The current–potential difference characteristics of an electrical component are shown below
a) Name the component. ....................................................................................................(1)
b) (i)Calculate the resistance of this component when the potential difference is+0.60 V
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Resistance = .............................(2)
(ii) State its resistance when the potential difference is –0.80 V
.................................................................................................................................... (1)
c) State a practical use for this component
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(Total 5 marks)
Question 24:
a) Define resistivity
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b) (i)The heating element used in a hairdryer consists of a long nichrome wire coiled around an
insulator. The hairdryer operates at 230 V and has a power of 1.0 kW. Calculate the
resistance of the heating element
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Resistance =.................................. (3)
(ii) The wire has a cross-sectional area of 1.3 × 10 –7m2. The resistivity of nichrome is1.1 ×10–6
Ω m. Calculate the length of the nichrome wire
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Length =.................................. (3)
(iii)The nichrome wire in this heating element has a diameter of 0.41 mm. A manufacturer
wishes to make a hairdryer of the same resistance but using half the length of nichrome
wire. What diameter wire must be used?
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Diameter = ..................................(2)
(Total 10 marks)
Question 25:
a) Define the term electromotive force (e.m.f.)
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b) A battery of e.m.f. 3.0 V is connected to a 5.0 Ω resistor with a very high resistance voltmeter
placed across the resistor.
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(i) The very high resistance voltmeter gives a reading of 2.8 V. Show that the internal
resistance of the battery is about 0.4 Ω
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(ii) A voltmeter with a resistance of 10 Ω is used instead of the original one. Calculate the
combined resistance of this voltmeter and the 5.0 Ω resistor
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Combined resistance = ..................................(2)
(iii) Calculate the reading on this voltmeter

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Voltmeter reading =.................................. (3)
c) State and explain what the resistance of an ideal voltmeter should be
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(Total 12 marks)
Question 26:
An experiment is set up to investigate how the current I in a filament lamp varies with
the potential difference V across it. The components used are shown below
a) Readings are taken over the full range from 0 V to the cell’s maximum potential difference.
In the space below, draw a circuit diagram for this experiment. (2)
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b) (i)Sketch on the axes below the shape of the graph you would expect the results to give.
(ii) Explain the shape of your graph. You may be awarded a mark for the clarity of your
answer
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(Total 8 marks)
Question 30:
A portable games console has the option of using a rechargeable battery unit which is
recharged by connecting it to a mains adaptor. The adaptor has an input power of 2.5W at
a voltage of 230V.
a) Calculate the adaptor’s input current when it is in use
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Current =....................................................................... (2)
b) The adaptor’s output is marked as: 3 V 0.2 A 0.6 VA
(i) Explain why V A is a unit of power
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(ii) Calculate the efficiency of the adaptor
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Efficiency = ....................................................................... (2)
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(iii) Suggest and explain a reason for the efficiency being less than 100%
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c) (i)The battery unit takes a time of 6 hours to charge fully. Assuming the adaptor’s output
current remains constant, calculate the amount of charge which flows from the adaptor
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Charge =....................................................................... (2)
(ii) Calculate the work done by the adaptor
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Work done = .......................................................................(3)
(Total 12 marks)
Question 32:
Modern technology makes wide use of light-emitting devices. For many years, however,
their use was limited by the lack of materials that could emit blue light efficiently.
a) State one property of blue light which is different from red light
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b) Physicists found that by adding indium to the semiconductor gallium nitride they could vary
the band gap energy of the material from 2.0 to 3.4 eV and so produce a range of light from
red to blue.
(i) Calculate the frequency range which corresponds to the above band gap energies
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Frequency range = ....................................................(3)
(ii) The following diagrams show the ground state and one excited state for the
semiconductor when it is being used to emit red and blue light. Decide which diagram is
showing the band gap of the blue light emitter and add an arrow to show the electron
transition that occurs during the emission of a blue light photon.
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___________________________ ___________________________ (2)
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c) The physicists also found that after this semiconductor material had been heated strongly in
nitrogen its resistivity had dropped from 106 Ω cm to just 2 Ω cm.
(i) State one advantage of this drop in resistivity when the semiconductor is in use
.......................................................................................................................................... (1)
(ii) The length of a rectangular sample of the semiconductor is 0.5 cm. Its width is 0.3cm and
its thickness is 0.4 mm. Calculate the resistance across its length when the resistivity is 2
Ω cm
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Resistance = .............................................................(3)
(Total 10 marks)
Question 34:
The current I in a conductor of cross-sectional area A is given by the formula
I =n A Q v
Where Q is the charge on the charge carrier
a) State the meanings of n and v.
n: .................................................................................................................................
v: ..................................................................................................................................
(2)
b) Show that the equation is homogeneous with respect to units
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c) Two pieces of wire A and B are made of the same material but have different diameters.
They are connected in series with each other and a power supply.
(i) Which terms from the above equation will be the same for both wires?
......................................................................................................................................... (1)
(ii) The diameter of A is twice that of B. Calculate the ratio vA : vB
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(Total 8 marks)
Question 35:
A and B are two lamps
a) Lamp A is rated at 12 V, 24W. Calculate the current in the lamp when it operates at its rated
voltage
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Current in lamp A=.............................. (2)
b) Lamp B is rated at 6.0 V. When it operates at its rated voltage, the current in it is 3.0 A.
Lamps A and B are connected in a circuit as shown below. The values of R1and R2 are chosen
so that both lamps operate at their rated voltage.
(i) State the reading on the voltmeter

............................................................................................................................................ (1)
(ii) Calculate the resistance of R2
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Resistance of R2 = .............................. (3)
(iii) Calculate the current in R1

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Current in R1= .............................. (1)
(iv) Calculate the potential difference across R1
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Potential difference =.............................. (1)

(v) Calculate the resistance of R1
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Resistance of R1= .............................. (1)
(Total 9 marks)
Question 36:
A cell of e.m.f. ε and internal resistance r is connected in a circuit with a resistor of resistance R
.The current in the circuit is I
a) Using the symbols in the diagram, write down a formula for

(i) the rate of conversion of chemical energy in the cell,
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(ii) the power dissipated in the resistor of resistance R,
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(iii) the power dissipated in r
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(3)
b) Use these formulae to write an equation based on conservation of energy in the circuit
................................................................................................................................................ (1)
c) The current I in the above circuit is given by the formula I=ε/(R+r). A laboratory E.H.T. supply
is designed to produce a maximum potential difference of 5 kV. Give atypical value for the
internal resistance of this supply and explain why it has this value
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(Total 7 marks)
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Question 39:
A gardener installs a solar powered fountain in a sunny part of his garden. He has the following
data about the solar panel from the manufacturer.
Under best conditions:
Voltage across terminals12.0 V
Power available5.9 W
The solar panel provides power to a water pump.
a) (i)Calculate the maximum current in the pump. Assume that the resistance of the connecting
cable is negligible
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Current = .......................................................... (2)
(ii) Show that the electrical resistance of the pump is about 24 Ω
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b) He decides to install another identical fountain in a shady area of the garden. He has to place
the solar panel some distance away from the pump so that it is in the sunlight. He then uses
a much longer connecting cable. The connecting cable to this pump has a total resistance of
2.0 Ω. The circuit is equivalent to that shown below.
Calculate
i) the current in this circuit
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Current =.......................................................... (2)
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(ii) the power available to the pump

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Power = ............................................................ (2)
c) State one way in which the power available to the pump in the shady area could be
improved. The positions of solar panel and fountain cannot be changed
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(Total 9 marks)
Question 44:
Listed below are five physical quantities.
Charge current potential difference resistance resistivity
Select from this list the quantity that fits each description below. You may use each quantity
once, more than once or not at all.
(i) A quantity which can be measured in joules per coulomb

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(ii) A quantity which equals the product of two other quantities in the list
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(iii) A quantity which equals the rate of change of another quantity in the list
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(iv) A base quantity in the SI system
(v) ......................................................................................................................................
(Total 4 marks)
Question 45:
a) A thermistor has a negative temperature coefficient. Explain with reference to the equation
I =nAQv what happens to its resistance when its temperature increases
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b) This thermistor is connected as shown in the diagram. Assume the battery has negligible
internal resistance.
This circuit can be used as an electrical thermometer to monitor the temperature of a water
bath.
(i) State how each meter responds when the temperature of the water is decreased.
Ammeter: ..........................................................................................................
Voltmeter: .........................................................................................................
(2)
(ii) Which meter is used to indicate temperature?
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(1)
(iii) State another assumption that you made
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(1)
(Total 7 marks)
Question 46:
The graph shows the I–V characteristics for two conductors. One is a length of nichrome wire
and the other is the tungsten filament of a lamp.
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a) Making reference to Ohm’s law, explain the shape of the tungsten filament graph. You may
be awarded a mark for the clarity of your answer
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b) (i)Calculate the resistance of the tungsten filament when the potential difference across it is
8.0 V
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Resistance = ...............................(2)
(ii) Both conductors are connected in parallel with an 8.0 V supply. Calculate the current that
will be drawn from the supply
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Current = ...............................(2)
(Total 8 marks)
Question 47:
A heater used on the rear window of a car consists of five strips of a resistive material joined as
shown in the diagram.
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When it is in use, the potential difference applied to the heater is 12 V and the heater
generates32 J of energy each second.
a) (i)Calculate the total resistance of the heater

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Total resistance = ............................... (2)
(ii) Calculate the resistance of a single strip
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Resistance = ............................... (2)
–8
b) Each strip has a cross-sectional area of 4.0 × 10 m and is made from a material of2
resistivity 1.1 × 10 –6Ω m. Calculate the length of each strip

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Length = ............................... (3)
c) The car manufacturer wants the rear window heater to be more powerful. Explain how this
could be achieved without altering the dimensions of the individual strips or the potential
difference across them
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(2)
(Total 9 marks)
Question 48:
a) Define the e.m.f. of a battery
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b) (i)A battery of e.m.f. ε and internal resistance r is connected into a circuit as shown below.
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When the switch is open the voltmeter reads 12.0 V and when the switch is closed it reads
8.0 V. Calculate the current in the circuit when the switch is closed
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Current = ............................... (2)
(ii) Determine the value of r
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r =............................... (2)
(iii) The switch remains closed. Calculate the power dissipated in the 4.0 Ω resistor
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Power = ............................... (2)
(iv) Calculate the energy wasted in the battery in five minutes

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Energy = ............................... (3)
(Total 10 marks)
Question 55:
A student investigates the use of rechargeable cells in a torch.
The diagram shows the circuit used to obtain readings of voltage and current for the torch bulb.
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The results obtained are voltage = 2.68 V, current = 0.31 A.

a) (i) Calculate the resistance of the torch bulb.
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Resistance =................................................................... (2)
(ii) The cells form a battery with an emf of 2.80 V.

Show that the internal resistance of the battery is about 0.4 Ω.
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(iii)Comment on how well these values match the necessary condition for maximum power
transfer between the battery of cells and the torch bulb.
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b) Each cell is labelled: ‘capacity 2 A h’. (A h is amp hours).
(i) Show that this corresponds to a total stored charge of about 14 000 C for the battery of
two cells.
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(ii) Calculate the time for which the battery could maintain a current of 0.31 A in the torch
bulb.
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Time =............................................................................ (2)
c) The internal resistance of the cells increases as they are used. Explain what effect this will
have on the efficiency of the system.
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(Total 12 marks)
Page 19 of 68
Question 58:
Railway signals rely on a combination of resistors to trigger the correct colour of light. Figure 1
shows a simplified version of the circuit used. The relay can be considered to be equivalent to a
resistor. When the potential difference across the relay is above 3 V it switches on the green
signal. The signal is red when the relay potential difference is less than this value.
a) The ratio of potential differences across the resistors in this circuit varies as the resistances
change. What name is given to a circuit such as this which makes use of multiple resistors in
this way?
................................................................................................................................................ (1)
b) The variable resistor is set to 10 Ω. Τhe relay resistance is 5.0 Ω. Calculate the potential
difference across the relay. Assume the railway track has negligible resistance.
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Potential difference =................................................................ (1)
c) The track is laid in sections of 100 m, with a length l between the rails. Each section of track
is insulated from the next section. Ballast, usually made of broken up rock, is used to
support the track as shown in Figure 2.
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(i) The ballast has a depth of 5.0 cm and a resistivity of 3.4 × 10 2 Ω m. Show that the
resistance of this 100 m section of ballast between the rails is about 100 Ω.
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(ii) The ballast resistance is in parallel with the relay. Calculate the combined resistance due
to the above section of ballast and the 5.0 Ω relay.
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Resistance =........................................................ (2)
(iii) How does the value of the potential difference across the relay and ballast compare with
the potential difference across the relay alone?
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(iv) When a train is on the track the current flows through the wheel axle from rail to rail
causing a short-circuit in parallel with the relay. What would the effect be on the
potential difference across the relay?
………………..........................................................................................................................(1)
(v) When wet the ballast resistance drops considerably and may become as small as 0.5 Ω.
Explain the consequence of this drop in resistance in terms of the signal lights.
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(Total 11 marks)
Question 59:
A 240 V 60W light bulb has a tungsten filament which has a working temperature of 2600 °C.
a) Calculate the resistance of the tungsten filament at this temperature.

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Resistance =................................................ (2)
b) The filament has a cross-sectional area of 3.1 × 10–10m2. Tungsten contains 3.4 × 1028 free
electrons per cubic metre. Determine the drift speed of the electrons in the filament when
the current is 0.25 A.
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Drift speed =............................................... (3)
c) Explain fully why the resistance of a tungsten filament increases with temperature.
You may be awarded a mark for the clarity of your answer.
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(Total 9 marks)
Question 60:
A student sets up the following circuit using a cell of e.m.f.  and internal resistance r.
a) Complete the equation for the total e.m.f. in terms of the other quantities given in the
diagram.
= (1)
b) He measures the current I for different values of resistance R. He then plots a graph of R
against 1/I.
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The equation for this graph is

R= /I -r
(i) Show how this equation is derived from the one you have stated above.
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................................................................................................................................................. (1)
(ii) Use the graph to determine the value for the e.m.f. of the cell. Show all your working.
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E.m.f. =................................... (2)
(iii)Show that when the external resistance is 5  the power dissipated in that resistance is about
0.3W.
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c) The student repeats the experiment adding an identical cell in series. Draw on the graph the
result of this experiment. (3)
(Total 10 marks)
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Question 61:
A variable resistor consisting of a wire and sliding contact has three terminals labelled K, L and
M.
The variable resistor is connected in series with a 6.0 V supply of negligible internal resistance,
an ammeter and a 20 Ω fixed resistor.
a) Label the terminals K, L and M on Figure 2. (1)
b) (i) The variable resistor has a maximum resistance of 10 Ω. The resistance of the fixed
resistor is 20 Ω. Determine the potential difference across the resistor when the sliding
contact is at the mid-point of the variable resistor.
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Potential difference = ................................................. (3)
(ii) What assumption have you made about the ammeter?

.......................................................................................................................................... (1)
c) The same components can be used in a second circuit to vary the potential difference across
the fixed resistor fully from 0 V to 6.0 V. Draw the circuit diagram for this potential divider
arrangement.
(3)
(Total 8 marks)
Question 66:
A student connects a circuit to find the resistance of a washing machine heating element.
a) Complete the circuit diagram below and explain how he uses it to obtain the necessary
measurements to calculate resistance.
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b) The following results are obtained.

Voltage = 3.00 V
Current = 0.12 A
Calculate the resistance of the element from these values.
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Resistance = ............................ (2)

c) The element is marked “1800W, 230 V”.
Calculate the resistance of the element in normal use.
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Resistance =............................ (2)
d) Explain why the two values of resistance you have calculated are different.
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(Total 8 marks)
Question 71:
A child wants to power his model train set from a 12 V battery. He also wants to be able to
control the speed of his trains.
His sister is studying physics and suggests using the following circuit.
She has the following materials to choose from to make the resistor.
a) The resistivity of the materials varies greatly. What type of scale could be used to plot them
most easily on a graph?
…............................................................................................................................................ (1)
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b) (i) She chooses a carbon rod. Explain why this is a good choice.
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(ii) The carbon rod she uses has a cross-sectional area of 3.0 × 10 ±6m2 and a length of 40 cm.
Show that the total resistance of the carbon rod is about 2
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(iii) Assuming that the internal resistance of the battery and the resistance of the connecting
wires is negligible, state the potential difference available to the train set when the
sliding contact is at:
X.................................................... Y....................................................
(1)
(iv) The total resistance of the wires connecting the battery to the resistor is about0.5 Ÿ.
Explain whether this would have a significant effect on the potential difference available
for the train set
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(Total 9 marks)
Question 72:
a) (i) Write the word equation that defines potential difference

................................................................................................................................................ (1)
(ii) The unit of potential difference is the volt. Express the volt in terms of base units only
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
.......................................................................................................................................... (3)
b) A 6.0 V battery of negligible internal resistance is connected to a filament lamp. The current
in the lamp is 2.0 A.
Page 27 of 68
Calculate how much energy is transferred in the filament when the battery is connected for 2.0
minutes
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
.........................................................................................................................................................
Energy transferred = ………………………. (3)
(Total 7 marks)
Question 73:
The current I in a conductor of cross-sectional area A is given by the formula

I =nAQv
Where:
Q: is the charge on a charge carrier.
a) What quantities do n and v represent?
n:
……………………….................................................................................................................................
v:
..................................................................................................................................................... (2)
b) A student has a metal conductor and a plastic insulator of the same dimensions. He applies
the same potential difference across each. Explain how the relative values of n for the metal
conductor and plastic insulator affect the current in each
......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
................................................................................................................................................ (2)
Page 28 of 68
c) The student connects two pieces of copper wire, A and B, in series with each other and a
battery. The diameter of wire A is twice that of wire B. Calculate the ratio of the drift velocity
in wire A to the drift velocity in wire B and explain your answer
......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
................................................................................................................................................ (3)
(Total 7 marks)
Question 74:
The circuit shows a battery of negligible internal resistance connected to three resistors.
a) Calculate the potential difference across the 15Ω resistor

......................................................................................................................................................
Potential difference = …………………………... (1)
b) Calculate the current I1 in the 4.0 Ω resistor
......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
I1=…………………... (3)
c) Calculate the current I2 and the resistance R
......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
I 2 =……………………………….
R= ………………………………. (3)
(Total 7 marks)
Page 29 of 68
Question 75:
Graph A shows how the potential difference across a battery varies with the current supplied.
Graph B shows how the current in a filament lamp varies with the p.d. across it.
a) (i) Use graph A to determine the internal resistance and the e.m.f. of the battery
......................................................................................................................................................
......................................................................................................................................................
Internal resistance = …………………………….
e.m.f = ………………………………
(2)
(ii) The lamp is connected to the battery. Determine the current in the lamp
.......................................................................................................................................... (1)
(iii)Calculate the resistance of the filament lamp when it is connected to the battery
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
Resistance = ………………………….(2)
Page 30 of 68
b) (i) Draw a diagram of a circuit that would enable graph A to be plotted. (2)
ii) Describe how you would use this circuit to obtain the data for the graph
.................................................................................................................................................
.................................................................................................................................................
.................................................................................................................................................
............................................................................................................................................ (2)
(Total 9 marks)
Question 83:
A student carries out an experiment to determine the resistivity of iron using the circuit shown
below.
He uses iron wire with a diameter of 0.50 mm.

Show that the cross-sectional area of this wire is about 2 × 10–7 m2.
..........................................................................................................................................................
..................................................................................................................................................... (2)
Page 31 of 68
The table shows the results he obtained
Complete the third column and use the data to plot a graph of resistance against length ÷ area
on the grid below.
Page 32 of 68
Draw the line of best fit and use this to calculate the resistivity of iron.
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
Resistivity =.................................... (4)
Suggest an explanation for the anomalous results obtained in this experiment.
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (2)
(Total 11 marks)
Question 86:
Two filament lamps are designed to work from a 9.0 V supply but they have different
characteristics. The graph shows the current-potential difference relationship for each lamp.
a) The lamps are connected in parallel with a 9.0 V supply as shown.
Page 33 of 68
(i) Which lamp is brighter? Give a reason for your answer

..............................................................................................................................................
......................................................................................................................................... (2)
(ii) Determine the current in the supply

..............................................................................................................................................
.............................................................................................................................................
Current = …………………… (2)
(iii) Calculate the total resistance of the two lamps when they are connected in parallel
..............................................................................................................................................
..............................................................................................................................................
..............................................................................................................................................
..............................................................................................................................................
..............................................................................................................................................
Total resistance =................................................. (2)
b) The lamps are now connected in series to a variable supply which is adjusted until the
current is 0.8 A.
Compare and comment on the brightness of the lamps in this circuit

....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
............................................................................................................................................... (3)
(Total 9 marks)
Question 87:
A student connects a 9.0 V battery in series with a resistor R, a thermistor and a milliammeter.
He connects a voltmeter in parallel with the resistor. The reading on the voltmeter is 2.8 V and
the reading on the milliammeter is 0.74 mA.
Page 34 of 68
a) (i) Show that the resistance of R is approximately 4000Ω

......................................................................................................................................................
................................................................................................................................................ (2)
(ii) Calculate the resistance of the thermistor

................................................................................................................................................
................................................................................................................................................
...............................................................................................................................................
Resistance =…………………….. (2)
b) The thermistor is mounted on a plastic base that has steel sprung clips for secure connection
in a circuit board.
Another student is using an identical circuit except that the bare metal pins of his thermistor
are twisted together.
Page 35 of 68
Suggest an explanation for how the reading on this student’s milliammeter will compare with
that of the first student
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (3)
(Total 7 marks)
Question 88:
A battery of e.m.f. 6.0 V is connected to a 10Ω resistor as shown in the circuit diagram.
a) Define the e.m.f. of the battery

......................................................................................................................................................
......................................................................................................................................................
................................................................................................................................................ (2)
b) When the switch is open the voltmeter reading is 6.0 V. The internal resistance of the battery
is 0.40 Ω. Calculate the reading on the voltmeter when the switch is closed
......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
Voltmeter reading = ……………………… (3)
c) A second identical battery is connected in parallel with the first one. Describe and explain
qualitatively what would happen to the voltmeter reading if the switch remains closed
......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
................................................................................................................................................ (3)
(Total 8 marks)
Page 36 of 68
Question 91:
A student finds the following information in the instructions for an electric iron.
He knows that the iron is heated by a wire filament controlled by a thermostat. The thermostat
switches the current off when the required temperature is reached.
The student suggests that the filament will have a higher resistance at higher temperatures.
Explain why the resistance of a metal wire would be expected to increase with temperature
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (2)
The student investigates this for each setting by plugging the iron in until it reaches the
required temperature and then unplugging it from the mains power. He then uses a laboratory
d.c. power supply, ammeter and voltmeter to obtain the following results:
The resistances at 110 °C and 150 °C have been calculated.
Calculate the resistance of the filament at 200 °C

..........................................................................................................................................................
.........................................................................................................................................................
Resistance =............................................... (2)
Discuss whether the results support the student’s suggestion that the filament has a higher
resistance at higher temperatures
..........................................................................................................................................................
..................................................................................................................................................... (1)
Page 37 of 68
The student has a power meter to find the power when the iron is plugged into the mains
supply and the setting is .. (Silk/ wool).

The reading is 1200 W.
Calculate the voltage of the mains supply.

..........................................................................................................................................................
..........................................................................................................................................................
.........................................................................................................................................................
Voltage =............................................... (3)
(Total 8 marks)
Question 94:
Disposable battery testers are sometimes placed on the packaging of battery packs. When
placed across the battery terminals, the tester changes colour, depending on the amount of
current that the battery provides.
To make a battery tester, you start with a layer of conductive ink that gets wider from one side
to the other. The battery terminals are placed at A and B
This ink is 0.02 mm thick on one such tester. Show that the resistance of section 1 above is
about 30Ω. The resistivity ρ of the ink is 1.6 × 10 ±4 Ω.m
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (3)
Section 2 is 1.0 cm wide. Determine the total resistance between points A and B
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
Page 38 of 68
..........................................................................................................................................................
.........................................................................................................................................................
Total resistance =............................................... (3)
The conductive ink is red. This is covered by a layer of thermochromic ink, which gradually
changes from black to transparent when warmed.
In use, the tester is placed across the battery terminals. Current then flows in the conductive
ink. The thermochromic ink becomes transparent, allowing the colour underneath to become
visible.
Why does the thermochromic ink become warm?
..........................................................................................................................................................
..................................................................................................................................................... (1)
If the battery is low on charge, the thermochromic ink becomes transparent only in section 1 of
the tester. Explain why
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (2)
(Total 9 marks)
Question 97:
Below is a list of words associated with circuits.

Current Volt Resistance
Ohm Charge Ampere
For each of the following choose one example from the above list.
Base unit..............................................................................
Derived quantity...................................................................
Derived unit...........................................................................
Base quantity........................................................................
(Total 4 marks)
Page 39 of 68
Question 98:
Io is one of Jupiter’s moons. Some of the electrons released from the volcanic surface of Io have
an average velocity of 2.9 × 107m s -1 towards Jupiter. The distance between Jupiter and Io is 4.2
× 105 km.
a) Show that the time taken for these electrons to reach Jupiter is about 14 s
......................................................................................................................................................
................................................................................................................................................ (2)
b) In this way a current of 3.0 × 106A is created between Io and Jupiter. Calculate the number
of electrons that arrive at Jupiter every second
......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
Number of electrons =................................ (2)
c) State the direction of the current

................................................................................................................................................ (1)
(Total 5marks)
Question 99:
The circuit diagram shows a 12 V d.c. supply of negligible internal resistance connected to an
arrangement of resistors. The current at three places in the circuit and the resistance of two of
the resistors are given on the diagram.
a) Calculate the potential difference across the 4.0 Ω resistor

......................................................................................................................................................
......................................................................................................................................................
Potential difference =.................................. (1)
Page 40 of 68
b) Calculate the resistance of resistor R2

......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
Resistance of R2=...................................... (2)
c) Calculate the resistance of resistor R1
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
...................................................................................................................................................
Resistance of R1=...................................... (3)

(Total 6 marks)
Question 100:
The circuit shown is used to produce a current-potential difference graph for a 12 V, 24 W

filament lamp.
a) Calculate the current in the filament lamp when the potential difference across it is 12 V
......................................................................................................................................................
......................................................................................................................................................
Current =...................................... (2)
b) (i) Sketch a graph of current against potential difference for this filament lamp
Page 41 of 68
(ii) Explain, with reference to the filament, the shape of your graph, as the potential
difference across the filament increases from 0 V to 12 V
..............................................................................................................................................
..............................................................................................................................................
..............................................................................................................................................
..............................................................................................................................................
..............................................................................................................................................
..............................................................................................................................................
......................................................................................................................................... (4)
(Total 8 marks)
Question 101:
a) A student sets up a circuit and accidentally uses two voltmeters V 1 and V2 instead of an
ammeter and a voltmeter. The circuit is shown below
(i) Circle the voltmeter which should be an ammeter. (1)
(ii) Both voltmeters have a resistance of 10 MŸ. The student sees that the reading on V2 is 0
V. Explain why the potential difference across the 100 Ÿ resistor is effectively zero
..............................................................................................................................................
..............................................................................................................................................
..............................................................................................................................................
......................................................................................................................................... (2)
b) The student replaces the 100 Ÿ resistor with another resistor of resistance R. The reading on
V2 then becomes 3.0 V.
(i) Complete the circuit diagram below to show the equivalent resistor network following
this change.
Label the resistor R.
Page 42 of 68
(ii) Calculate the value of R

................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
R=.............................................................. (3)
(Total 8 marks)
Question 108:
The following notes are taken from some laboratory instructions for using an ohmmeter to
measure resistance.
• Ohmmeters should be zeroed. To do this, touch the leads together and adjust the meter to
read zero ohms.
• The ohmmeter works by placing a small voltage across the resistor. The current that flows in
response to this voltage determines the ohmmeter reading.
• Do not measure the resistance of a resistor while it is in a circuit.
Explain why touching the leads together allows the meter to be zeroed
..........................................................................................................................................................
..................................................................................................................................................... (1)
An ohmmeter is connected across a resistor. The ohmmeter applies a voltage of 0.54 V. The
current through the meter is 0.0081 A. Show that the resistance being measured is about70
..........................................................................................................................................................
..................................................................................................................................................... (2)
Explain why, when using an ohmmeter, the resistance of the resistor should not be measured
while it is in a circuit
..........................................................................................................................................................
..........................................................................................................................................................
Page 43 of 68
..........................................................................................................................................................
..................................................................................................................................................... (2)
By connecting the ohmmeter across a coil of thin copper wire, temperature changes can be
detected.
Explain how, as the temperature rises, changes in the copper lead to changes in the meter
reading
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (3)
(Total 8 marks)
Question 110:
To preserve food effectively, packaging film must isolate food from bacteria in the
environment. The film is thoroughly inspected for holes, but many inspection techniques can
damage it.
A new technique has been developed to check the film. The film is passed between a roller
electrode and a conducting liquid, in which a second electrode is placed, as shown below. The
resistance between the two electrodes is measured; even a pinhole in the film can greatly
reduce this resistance by filling with the liquid and creating a conducting path
Complete the diagram above showing a circuit you could use to measure this resistance. (2)
For undamaged film the resistance measured between the electrodes is very high. Show that
when a circular hole of diameter 1.0 × 10 -4 m is present and fills with the conducting liquid the
resistance measured is about 170 Ÿ. Assume that the resistance through the liquid between the
Page 44 of 68
lower electrode and the film is so small it can be ignored. Resistivity of conducting liquid = 2.7 ×
10 -3 Ω.m, film thickness = 5.0 × 10-4m
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (3)
Using this technique, the following values of resistance were obtained.
Plot a graph of resistance against diameter from these results on the grid below.
Page 45 of 68
Use the graph to determine the diameter of the hole which gives a resistance of 30Ω
..................................................................................................................................................... (1)
(Total10marks)
Question 113:
A student connects the circuit as shown in the diagram.
Page 46 of 68
The reading on the voltmeter is 1.8 V. Calculate the current in the resistor
..........................................................................................................................................................
.........................................................................................................................................................
Current =............................................... (1)
Calculate the resistance of the thermistor
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
Resistance =........................................ (2)
The graph shows how the resistance of the thermistor depends on its temperature.
Determine the temperature of the thermistor.

Temperature =...................................... (1)
If the e.m.f. of the supply were doubled, would the reading on the voltmeter double? Explain
your answer
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
.................................................................................................................................................... (3)
(Total 7marks)
Question 114:
A student is asked to carry out an experiment to find the resistivity of the material of a length of
resistance wire. Draw an appropriate circuit diagram. (2)
Page 47 of 68
List all the measurements the student should take to find the resistivity
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (3)
How should these measurements be used to find the resistivity?

..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (3)
Suggest two precautions the student should take to ensure an accurate result
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (2)
(Total 10marks)
Question 115:
Modern electric showers need to be very powerful because they are required to heat the water
flowing through them very quickly.
The shower is connected to the electrical supply by a copper cable 15 m long. A conductor
inside the cable has a cross-sectional area of 6.0 × 10 -6 m2. The resistivity of copper is 1.7 × 10- 8
m. Find the resistance of the conductor
..........................................................................................................................................................
..........................................................................................................................................................
Resistance =......................................... (3)
The conductors used for most electrical circuits in homes are copper but they have a smaller
cross-sectional area. Suggest why the manufacturer of the shower recommends that the thicker
wire is used in the shower cable
..........................................................................................................................................................
..................................................................................................................................................... (2)
(Total 5marks)
Question 116:
A 12 V car battery is recharged by passing a current of 5.0 A through it in the reverse direction
using a 15 V battery charger. The internal resistance of the charger and the battery are 0.56Ω
and 0.04Ω respectively. The circuit used is shown below.
Page 48 of 68
The terminal p.d. across the battery charger is found by solving the following equation:
Terminal p.d. = 15 V - (5.0 A × 0.56Ω)
Determine the reading on the voltmeter

..................................................................................................................................................... (1)
Write an equivalent equation for the terminal p.d. across the battery
..........................................................................................................................................................
..................................................................................................................................................... (3)
Calculate the rate at which energy is being wasted during the recharging process
..........................................................................................................................................................
..........................................................................................................................................................
Rate =.................................................. (2)
Hence determine the efficiency of the recharging process

..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
Efficiency =.......................................... (2)
The internal resistance of this car battery is 0.04 Ω. Explain why a car battery is designed to
have a very low internal resistance
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (2)
(Total10 marks)
Page 49 of 68
Question 120:
A student does some measurements on two light-emitting diodes (LEDs). She measures the
current I through them at a series of voltages. Her results are shown in the table.
Complete the circuit diagram below to show a circuit that she could have used to obtain these
results.
Page 50 of 68
For both LEDs, the current varies in a similar way. Describe in words this variation
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (3)
Discuss whether the LEDs obey Ohm’s law

..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (2)
Calculate the resistance of the green LED when it has 1.9 V across it
..........................................................................................................................................................
..........................................................................................................................................................
Resistance =.......................................... (2)
Calculate the power dissipated by the red LED when it has 1.7 V across it
..........................................................................................................................................................
..........................................................................................................................................................
.........................................................................................................................................................
Power =................................................ (2)
(Total 12 marks)
Question 123:
State the word equation that is used to define charge.

..........................................................................................................................................................
..................................................................................................................................................... (1)
Define potential difference

..........................................................................................................................................................
..................................................................................................................................................... (1)
A 9.0 V battery of negligible internal resistance is connected to a light bulb.
Page 51 of 68
Calculate the energy transferred in the light bulb when 20 C of charge flows through it
..........................................................................................................................................................
..........................................................................................................................................................
.........................................................................................................................................................
Energy =..................................................... (2)
(Total 4 marks)
Question 124:
A polythene rod was negatively charged by rubbing it with a cloth. The rod was then stroked
several times across the metal cap of a meter used for measuring charge.
The initial reading on the meter was zero.

After 3.8 s the final reading was –6.4 × 10–8 C.
Calculate the number of electrons that were transferred to the metal cap.
……….…………………………………………………………………………….…….……………….………………………………………
……………………………………………………………………………………………………………………………………………………
Number of electrons = …….………… (3)
Calculate the average rate in C s–1 at which charge was transferred to the metal cap.
…….……………………………………………………………………………………………….……….……………………………………
…………………………………………………………………………………………………………………………………………………….
Rate = …………..……… C s–1 (2)

State the base unit for the rate of flow of charge.
………………………………………………………………………………………………………………………………………………. (1)
(Total 6 marks)
Page 52 of 68
Question 125:
A light-emitting diode (LED) is a diode that emits light when it conducts. Its circuit symbol is
A student connects the circuit shown below
She notices that the reading on the high resistance voltmeter remains at 0 V as she slides the
contact between terminals A and B.
Explain this observation as fully as you can

..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (2)
The student then disconnects the LED and reconnects the circuit as shown below. She intends
to vary the intensity of the light emitted by the LED by sliding the contact between terminals A
and B
Page 53 of 68
The student cannot detect any light emitted by the LED. Briefly explain why the LED is so dim
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (2)
Draw the circuit that the student should have connected using this apparatus in order to vary
the brightness of the LED and measure the potential difference across it. (3)
(Total 7 marks)
Question 126:
A solar cell is a device that generates a potential difference when certain wavelengths of the
electromagnetic spectrum are incident on it.
The circuit symbol for a solar cell is
The solar cell is used in a circuit with a variable resistor, an ammeter and a voltmeter. Readings
of current I in the circuit and the terminal potential difference V across the solar cell are used to
plot a graph of I against V. Draw a suitable circuit diagram. (2)
The graph shows a set of results obtained in this way. The intensity of the light incident on the
cell remained constant while the readings were obtained
Page 54 of 68
Calculate the power output of the cell at the point marked X on the graph
..........................................................................................................................................................
..........................................................................................................................................................
Power =......................................................... (2)
Describe the variation of the power output of the cell as the current increases from zero to its
maximum value
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (3)
State the e.m.f. of the cell

..................................................................................................................................................... (1)
Calculate the internal resistance of the cell when it is operating under the conditions
represented by point X
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
Internal resistance =...................................... (2)
(Total 10marks)
Page 55 of 68
Question 127:
Tick whether the following statements are true or false. In each case explain your reasoning.
Statement 1
When a battery is connected across a thick wire in series with a thin wire of the same material,
the electrons move faster through the thick wire.
Explanation.......................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (3)
Statement 2
When a battery is connected across a high resistance in parallel with a low resistance, more
power is dissipated in the low resistance.
Explanation.......................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
...........................................................................................................................………………………..(3)
(Total 6 marks)
Question 132:
A student models a stage lighting system using a circuit-drawing computer package and a
spreadsheet. He starts with a power supply of e.m.f. 120 V, and internal resistance 15 Ω. He
assumes that each lamp has fixed resistance 60 Ω. He is interested in the effect of turning on
the lamps one at a time, so that the number of lamps switched on increases from one to six. His
circuit and part of his spreadsheet are shown below.
Page 56 of 68
The student has assumed that the voltmeter would have no effect on any of the values he has
calculated. Explain why this is an appropriate assumption
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (1)
When 6 lamps are on (row 8), how much current flows through lamp X?
..........................................................................................................................................................
.........................................................................................................................................................
Current through X =............................................... (1)
Calculate the value missing from cell E7

..........................................................................................................................................................
.........................................................................................................................................................
Value =.................................................................. (1)
The lamp marked X is the first to be switched on. Explain how lamp X would appear as
successive lamps are switched on
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (3)
What would be a suitable formula for calculating cell C6?

..........................................................................................................................................................
..................................................................................................................................................... (2)
Page 57 of 68
Comment on how the internal resistance of the power supply affects the way in which the
values in column E vary
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (2)
(Total10marks)
Question 136:
Resistivity measurements under the sea have been used to find new sources of fresh water.
Two probes are towed along the seabed behind a small boat
Taking measurements using these probes, resistivity can be calculated at various depths below
the seabed
What measurements are needed to calculate resistivity?

..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (3)
The diagram below displays the resistivities measured in a survey
Page 58 of 68
Line A below has been plotted using some of this data. It shows how resistivity ρ varies with
depth below the seabed 2.0 km from the shore.
Make measurements from this graph to determine the equation of line A

..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (3)
Use the survey results to add another line to show how resistivity varies with depth 2.4 km
from the shore. (3)
The resistivity gradient (the variation of resistivity with depth) is greater in areas where there is
fresh water below the seabed. Suggest the best distance from the shore to drill for fresh water
..................................................................................................................................................... (1)
(Total 10marks)
Page 59 of 68
Question 139:
Four 10 Ω resistors are connected as shown in the diagram
Calculate the total resistance of the combination

..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
.........................................................................................................................................................
Total resistance =................................. (3)
Comment on your answer and suggest why such a combination of resistors might be used
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (2)
(Total 5marks)
Question 140:
Use the axes to draw the current-voltage characteristic of a diode.
Page 60 of 68
Use the axes to draw the current-voltage characteristic of a filament lamp.
(Total 6marks)
Question 141:
A cell of negligible internal resistance is connected in series with a micro ammeter of negligible
resistance and two resistors of value 15 kΩ and 25 kΩ. The current is 150 µA. Draw a circuit
diagram of the arrangement.
(1)
Show that the e.m.f. of the cell is 6.0 V
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (2)
A voltmeter is now connected in parallel with the 25 k resistor. Draw a diagram of the new
circuit.
(1)
Page 61 of 68
When the voltmeter is connected the reading on the micro ammeter increases to 170 µA.
Calculate the resistance of the voltmeter
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
.........................................................................................................................................................
Resistance =......................................... (3)
(Total 7marks)
Question 142:
Lord Kelvin discovered that the electrical resistance of iron wire changed when the wire was
stretched or compressed. This is the principle on which a resistance strain gauge is based. Such
a gauge consists of a length of very fine iron wire cemented between two very thin sheets of
paper.
The cross-sectional area of the wire is 1.1 × 10-7m2 and the gauge length as shown in the
diagram is 2.4 × 10 -2m. The resistivity of iron is 9.9 × 10-8Ω m. Calculate the resistance of the
strain gauge
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
Resistance of strain gauge =.................................. (4)
When this gauge is stretched its length is increased by 0.1% but its cross-sectional area remains
the same. What is the change in the resistance of the gauge?
..........................................................................................................................................................
..........................................................................................................................................................
Change in resistance =........................................... (2)
Page 62 of 68
Explain the effect that stretching the wire will have on the drift velocity of electrons in the wire.
Assume that the other physical dimensions of the wire remain unchanged and that there is a
constant potential difference across the wire
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (3)
(Total 9mark)
Question 148:
A 40 mm strip of light-sensitive material is used in a camera with automatic focus.
The lens is moved automatically until light is sharply focused onto a very short length of this
strip. The graph shows how the resistance R of the total length of the strip varies with light
intensity.
Page 63 of 68
Calculate the resistance per mm of the strip when it is in complete darkness

..........................................................................................................................................................
..................................................................................................................................................... (2)
Bright light of intensity 10 units is focused on an 8 mm length of the strip.

Show that the resistance of the 8 mm length is 40Ω
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (2)
The remainder of the strip is in the dark. Calculate its resistance

..........................................................................................................................................................
..................................................................................................................................................... (1)
A cell of e.m.f. 1.2 V and negligible internal resistance is connected across the ends of the strip.
Calculate
The current in the strip

..........................................................................................................................................................
..........................................................................................................................................................
The p.d. across the 8 mm length

..........................................................................................................................................................
..................................................................................................................................................... (4)
Explain why this current decreases as the bright light is more sharply focused onto a smaller
length of the strip
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (2)
(Total11marks)
Question 153:
A student is provided with two filament lamps A and B. Each is rated 12 V 60 W, but lamp A has
a carbon filament and lamp B a tungsten filament
Calculate the resistance of each filament lamp under normal operating conditions
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
.........................................................................................................................................................
Resistance =.............................................. (3)
Page 64 of 68
The graph shows the relationship between the current I and the potential difference V for the
two filament lamps
Describe how the resistances of lamp A and lamp B vary with current.
Lamp A:
..........................................................................................................................................................
..........................................................................................................................................................
Lamp B:
..........................................................................................................................................................
..................................................................................................................................................... (2)
The diagram shows the two filament lamps connected in series across a battery of e.m.f 12 V
and negligible internal resistance. Both filaments glow dimly, but the hlank filament of lamp A is
the brighter
Page 65 of 68
Why does each filament glow only dimly?

..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (1)
Suggest why the filament of lamp A is the brighter

..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (2)
(Total 8 marks)
Question 154:
A 500 W electric toaster operates from the 230 V mains. Calculate the current in the heating
element of the toaster
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
.........................................................................................................................................................
Current =........................................................ (3)
The heating element of the toaster is made of much thinner wire than the wire in its supply
cable. In which of these two wires do the electrons have the greater drift velocity?
..................................................................................................................................................... (1)
Explain your answer. You may be awarded a mark for the clarity of your answer
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (4)
(Total 8 marks)
Question 155:
The diagram shows a type of resistor commonly used in electronic circuits
Page 66 of 68
It consists of a thin film of carbon wrapped around a cylindrical insulator. The diagram below
(not to scale) shows a typical film of carbon, resistivity ρ, before it is wrapped round the
insulator.
Show that the resistance R of the carbon film is given by: ρl/wt
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (2)
This film has length l= 8.0 mm, width w= 3.0 mm and thickness t =0.0010 mm (i.e. t= 1.0 ×
106m).
If the resistivity of carbon is 6.0 × 10-5Ω m, calculate the resistance of the carbon film
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
Resistance =.................................................. (3)
Show that the resistance of a square piece of carbon film of uniform thickness is independent of
the length of the sides of the square
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (2)
(Total 7 marks)
Question 156:
Define the term e.m.f. of a cell

..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... (2)
Page 67 of 68
A student wants to use a graphical method to determine the internal resistance r of a cell of
known e.m.f..
Complete the diagram below showing how the cell should be connected in a circuit to allow the
student to do this.
Sketch the graph the student should plot and state how she could determine r from the graph
..........................................................................................................................................................
..................................................................................................................................................... (2)
(Total 6 marks)
Page 68 of 68

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KHALID YOUSEF AL HINDI @ELECTRICITY QUESTIONS

a) What is wrong with his circuit diagram?

(ii) Use your graph to determine the e.m.f. of the cell.

a) Name the component. ....................................................................................................(1)

(iii) Calculate the reading on this voltmeter

___________________________ ___________________________ (2)

(i) State the reading on the voltmeter

(iii) Calculate the current in R1

Potential difference =.............................. (1)

a) Using the symbols in the diagram, write down a formula for

Under best conditions:

Voltage across terminals12.0 V

The solar panel provides power to a water pump.

(ii) the power available to the pump

Charge current potential difference resistance resistivity

(i) A quantity which can be measured in joules per coulomb

a) (i)Calculate the total resistance of the heater

resistivity 1.1 × 10 –6Ω m. Calculate the length of each strip

(iv) Calculate the energy wasted in the battery in five minutes

The results obtained are voltage = 2.68 V, current = 0.31 A.

(ii) The cells form a battery with an emf of 2.80 V.

b) Each cell is labelled: ‘capacity 2 A h’. (A h is amp hours).

a) Calculate the resistance of the tungsten filament at this temperature.

The equation for this graph is

a) Label the terminals K, L and M on Figure 2. (1)

(ii) What assumption have you made about the ammeter?

b) The following results are obtained.

Resistance = ............................ (2)

a) (i) Write the word equation that defines potential difference

The current I in a conductor of cross-sectional area A is given by the formula

a) What quantities do n and v represent?

a) Calculate the potential difference across the 15Ω resistor

He uses iron wire with a diameter of 0.50 mm.

The table shows the results he obtained

a) The lamps are connected in parallel with a 9.0 V supply as shown.

(i) Which lamp is brighter? Give a reason for your answer

(ii) Determine the current in the supply

Compare and comment on the brightness of the lamps in this circuit

a) (i) Show that the resistance of R is approximately 4000Ω

(ii) Calculate the resistance of the thermistor

a) Define the e.m.f. of the battery

The resistances at 110 °C and 150 °C have been calculated.

Calculate the resistance of the filament at 200 °C

supply and the setting is .. (Silk/ wool).

Calculate the voltage of the mains supply.

Below is a list of words associated with circuits.

c) State the direction of the current

a) Calculate the potential difference across the 4.0 Ω resistor

b) Calculate the resistance of resistor R2

Resistance of R1=...................................... (3)

The circuit shown is used to produce a current-potential difference graph for a 12 V, 24 W

(i) Circle the voltmeter which should be an ammeter. (1)

(ii) Calculate the value of R

Using this technique, the following values of resistance were obtained.

A student connects the circuit as shown in the diagram.

Determine the temperature of the thermistor.

How should these measurements be used to find the resistivity?

Determine the reading on the voltmeter

Hence determine the efficiency of the recharging process

_ _ (2)