Electricity Exercises 1
Electricity Exercises 1
Electricity Exercises 1
Electricity Exercises
1.
Which of the following statements is/are correct about the circuit above?
A) (1) only
B) (3) only
C) (1) and (3) only
D) (1), (2) and (3)
2. If the electron flow rate through a resistor is 3.76 x 1018 each second, what is the current
passing the resistor?
-19
(Given: Charge of an electron = -1.6 x 10 C)
A) 0.6 A
B) 2A
C) 1.88 x 1018 A
D) 6.25 x 1019 A
A
3. In the following circuit, if the p.d. (voltage) across bulb A is 3 V and the p.d. voltage
across bulb B is 2 V.
(1) The charge flow rate through bulb A is higher than that
through bulb B.
(2) Bulb A consumes 1 J of energy more than bulb B, for each
coulomb of charge.
(3) The current flowing in the bulb A is 5 A.
A) (1) only
B) (2) only
C) (1) and (2) only
D) (1), (2) and (3)
4. The e.m.f. of which of the following batteries is different from the others?
A) B)
C) D)
5. Which of the following is the correct connecting of a voltmeter for measuring voltage
across a resistor?
A) B)
C) D)
A) (1) only
B) (1) and (3) only
C) (2) and (3) only
D) None of the above
7. The relation of the current passing through a conducting wire changes with the voltage
across is shown in the figure below. If the temperature of the wire does not change when
current passes the wire.
A) (1) only
B) (2) only
C) (1) and (2) only
D) (2) and (3) only
When the current passes through the metal wire is 1 A, the temperature of the wire is
25 oC. What is the current passes through the metal wire when the temperature of the
wire is 200 oC?
A) 0.417 A
B) 0.6 A
C) 1 A
D) 1.5 A
A
10. In the following figure, if switch K is closed, then
11. Current of I amperes passes through a bulb for t minutes. How much charge has passed
through the bulb?
A) It C
B) 60It C
I
C) C
60t
t
D) C
I
12. Energy of 12 J is supplied when 6 C of positive charges pass through a supply. What is the
e.m.f. of the supply?
A) 2 V
B) 12 V
C) 24 V
D) 12 J
13. If each resistor in the following circuit is with resistance R,
4
A) R
3
B) 2R
8
C) R
3
D) 6R
14. In the following circuit, the e.m.f. of the battery is V and the resistance of each resistor
is R.
16. If each resistor in the following circuit is with resistance R. When the switch S is closed,
then
Reading of A1 Reading of A2
A) Increases Decreases
B) Decreases Increases
C) Increases Increases
D) Decreases Decreases
17. A student wants to measure the resistance of a resistor, and it is known that the
resistance is less than 10 ohms. Which circuit should be used?
A) B)
C) D)
18. In the following circuit, the resistance of R2 is half of that of R1. When S1 is closed, the
ammeter reads 1.6 A.
What is the reading of the ammeter when both S1 and S2 are closed?
A) 0. 6 A
B) 2.8 A
C) 3.6 A
D) 4.2 A
19. Four identical bulbs are connected as following circuit.
20. In the following circuit, the voltage across the battery is 2V. If the resistance of of R1 =
A,R2 = 2A, R3 = 3A and R4 = 4A, then what is the voltage across R3?
V
A)
3
3V
B)
10
6V
C)
31
12V
D)
31
21. In the following circuit, the voltage of the cell is 1 V, and the three resistors are
identical, each having a resistance of 1 i .
What is the ratio of the current passing through R1, R2 and R3?
A) 1 : 2 : 3
B) 3 : 2 : 1
C) 5 : 1 : 1
D) 5 : 3 : 1
Directions: Each question below consists of two statements. Decide whether each of the two
statements is true or false. If both are true, then decide whether or not the second
statement is a correct explanation of the first statement. Then select option A, B, C or D,
according to the following table.
D False True
1.
1st statement 2nd statement
The brightness of a bulb with fixed The larger p.d. across the bulb, the
resistance depends only on the p.d. more the energy is given to the bulb
across it. by each coulomb of charge.
2.
The resistance of a metal wire The metal wire does not follow Ohm's
increases with its temperature. law.
3.
When a resistor is added to a circuit, Equivalent resistance of a circuit
total current flowing in the circuit increases if resistors are connected in
must be decrease. series.
4.
When some resistors are connected Less current is drawn from the battery
to a battery, as compared with a when resistors are connected in series.
parallel circuit, the battery can last
longer if resistors are connected in
series.
5.
If bulbs connected in series, the Energy is given to the bulbs when
current passing them is different. current passes them.
7.
When a voltmeter is connected Voltmeter has a very high resistance.
across a resistor of small resistance,
there would be little current passes
through it.
8.
Birds can stand on an overhead high- Overhead high-voltage cables are
voltage cable without getting insulated by plastic coatings.
electric shock.
Short questions
1. The following diagram shows a labeled '15 Ω, 8 A' rheostat (variable resistor) connected
by wires.
battery
S1
S2
dashboard light
car body
(a) Does the student correct? Give reasons to support your answer.
(5 marks)
(b) How can the student connect the two sets of lights so that the total
brightness of the lights can be increased?
(1 mark)
4. A alarm clock is labeled as “3V”, and it needs two 1.5-V 'AA' cells to operate.
5. A torch requires three 1.5-V cells to work. When the switch is pushed up, the light bulb is
on.
(a) Calculate the current passing the bulb when the switch closed. (3 marks)
(b) Do charges are being used up, if not, then what is being used up in the circuit?
(1 mark)
(a) How does the brightness of the bulb change if the contact is moved towards A?
[1]
(b) If the labelled working voltage of the bulb is 1.5 V, where should be the position
of the contact placed? Show your calculation. (4 marks)
8. The following graph shows how the resistance changes with temperature of three
different materials.
(a) When a tungsten light bulb is switched on, how does the current change with the
first few minutes? Explain your answer.
(3 marks)
(b) Suggest an application for thermister and explain your answer.
(4 marks)
9. If a 7V rechargeable battery is labelled '1100 mAh', that means the battery can provide
1100 mA over one hour. If the camera operates for an hour at 1100 mA, how much charge
has passed the battery? (2 marks)
10. The following figure shows a variable resistor. The resistance of the resistor can be
changed when the contact moved.
11. A student finds that both of the following circuits can change the brightness of the bulb.
(a) Explain why circuit A and circuit B can change the brightness of the bulb briefly?
(4 marks)
(b) Which circuit may switch off the bulb? Why not the other circuit, explain briefly?
(3 marks)
12. A lighting system has three bulbs,
(a) Which way should the bulbs be connected, series or parallel. Suggest a method to
test the connection of the bulbs. (3 marks)
(b) Draw a circuit diagram to show how the bulbs and the switch are connected.
(3 marks)
(a) Draw a circuit diagram to show how the for the above circuit. (3 marks)
(b) What happens to the brightness the bulbs when the switch is closed if internal
resistance of the cells are negligible? Explain you answer briefly. (3 marks)
(c) What happens to the brightness the bulbs when the switch is closed if internal
resistance of the cells are NOT negligible? Explain you answer briefly. (3 marks)
14. A bulb is labeled as '3 V, 0.5 A' is connected in the circuit below.
12 V
A B
'3V, 0.5 A'
(a) A resistor should be connected across AB for the bulb to operate at its labeled
value. What is the resistance of that resistor? (3 marks)
(b) If only 15-Ω resistors are available, draw circuit to operate the bulb with 12V
supply. (2 marks)
15. A student connects the following circuit to find the resistance of the resistor with few
ohms.
(a) In the circuit, what are the readings of the voltmeter and ammeter?
(2 marks)
(b) Draw a correct circuit for the student to find the resistance of a resistor with few
ohms?
(2 marks)
16. The following figure shows the V-I graphs of two resistors X and Y.
(a) Which resistor has a higher resistance? Explain your answer. (2 marks)
(b) If X and Y are connected in series, in which region of the V-I graph, will the total
resistance of the circuit lie? (2 marks)
(c) If X and Y are connected in parallel, in which region of the V-I graph, will the total
resistance of the circuit lie?
(2 marks)
17. A student uses the following circuit to check the validity of the Ohm’s law (i.e. V = IR).
(a) If the resistance of the variable resistor is initially set to few ohms and then the
resistance of it is increased slightly, what do the ammeter’s and voltmeter’s readings
change? (2 marks)
(b) If the resistance of the variable resistor is increased to 20 ki, why the reading of the
ammeter and voltmeter do not follow the ohm’s law? (3 marks)
Long questions
1. (a) A student measures the voltage across a cell. With the following two circuits.
(b) The following circuit can be used to measure the internal resistance of two identical
cells.
The student the date of resistance and current in the following table. The results are
as follows:
R/W 25 10 5 2.5 1
I/A 0.1 0.2 0.3 0.4 0.5
(I) Write down the relation between the total voltage of the cells, internal
resistance of a cell r, current I and the resistance of variable resistor R.
(1 mark)
(ii) Using the data above find the internal resistance of cells.
(4marks )
(a) If the headlights each draws 4 A and the de-mister draws 2 A. The p.d. across the
battery drops from 14.6 V to 13.6 V when the headlights and de-misters are switched
on. Then find the internal resistance of the battery?
(2 marks)
(b) When the driver switches on the starter, 90 A pass through the starter. Then what
is the p.d. across the battery (internal resistance is NOT negligible)?
(3 marks)
(c) What is the voltage across the headlight while the starter motor and the de-
mister are in use? What happens to the brightness of the headlight when current is
passing through the starter? Explain briefly.
(3 marks)
(d) A car battery has to be replaced if its internal resistance increases to a certain
value. How does a high internal resistance affect the work of a battery.
(2 marks)
3. The following shows a set up of a circuit.
(a) Draw a circuit diagram the above setup with correct polarity of all apparatus.
(5 marks)
(b) How would the readings of the ammeter and the voltmeter change if the contact
of the rheostat moves to right? Explain your answer briefly.
(3 marks)
(c) The following table shows the reading of V and A:
(I) Describe the process of the above experiment to obtain the data above?
(3 mark)
(ii) Plot a graph of V against I on graph paper.
(4 marks)
(iii) If the length of the eureka wire is doubled. On the graph in (ii), sketch the
V-I relation.
(1 mark)
4. The following circuit is used to study the p.d. across the bulb and also the current is pass
through the bulb.
(b) Draw a circuit diagram for the above setup with correct polarity of all apparatus.
(5 marks)
(c)The following table shows the reading of the ammeter and voltmeter
p.d.across the bulb (V) / V 1.0 1.8 2.8 4.0 5.0 6.4
Current through the bulb (I) / A 0.3 0.6 0.9 1.3 1.6 1.9
5. (a) Draw a circuit diagram to show how to measure the resistance of a high power light
bulb (around 10 ohms only) by using the following component.
Component provided:
a battery box, an ammeter, a voltmeter, a switch, a rheostat, a light bulb,
several connecting wires
(5 marks)
(b) The following figure shows the voltmeter and the ammeter used in the experiment.
voltmeter
ammeter
(0 − 5 V)
(0 − 500 mA)
(I) What are the readings of the ammeter and the voltmeter means?
(2 marks)
(ii) What is the working power of the light, and how much energy is consumed
in 10 minutes? (3 marks)
(iii) What is the resistance of the light bulb? (2 marks)
(c) If the p.d. across it increases, how do the temperature and the resistance of the
light bulb change? (2 marks)
(a) The above circuit is suitable for measure a resistance with few ohms only,
explain it briefly. And draw a circuit diagram which is suitable for measure a
resistance with several thousands ohms. (5 marks)
(b) Figure b shows the voltmeter and the ammeter used in the experiment.
voltmeter ammeter
(0 − 5 V) (0 − 50 mA)
Figure b
(I) What are the readings of the ammeter and the voltmeter means?
(2 marks)
(ii) What is the resistance of the light bulb? (2 marks)
(c) Sketch a V-I graph for the above experiment, it is known that the temperature of
the filament of the bulb increase with the p.d. across it.
(4 marks)
(d) The variable resistor in the following circuit is use to control the pass the light
bulb.
(I) When the resistance of the variable resistor varies the change in the current
is very small. Why? (3 marks)
(ii) Modify a circuit so that a large change in the current when the variable
resistor varies. (2 marks)
7. The following circuit is used to find out the resistance of a eureka wire is affected by its
length.
Figure a
(I) Plot a graph to show the relation between the length and the resistance of
the eureka wire. (4 marks)
(ii) Write down the relationship between the resistance and the length?
(2 marks)
(iii) If the thickness of the metal wire increases, how would the resistance of
the wire be affected? (2 marks)
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