1. In normal use, the current in the television set is 0.31A.

(i) Explain how a

fuse works to protect the television set if there is a fault.
Ans: When the circuit exceeds the fuse rating, the thin metal wire in the fuse
melts.
2. A radio wave passes through the ground and refracts at the boundary
between soil and rock. The diagram shows three wavefronts of the wave
before and after refraction. The wave is also reflected at the boundary
between the soil and the rock. Complete the diagram to show three
wavefronts after the wave has been. Reflected at the boundary.

(ii) Explain why the radio waves passing through the rock have a smaller
wavelength than the radio waves passing through the soil.
Ans: The rock is more optically dense than soil. So, when the waves go from a
less dense to a more denser medium, the waves slow down and bends
towards the normal. The frequency of the waves remains constant. So as v=f,
when speed increases, wavelength also decreases. (The wavefronts also get
bigger.)
3. The drawing shows a camel and a person in a desert.
 4. Describe a method you could use to find the pressure a person exerts on
the ground when standing on two feet.
Ans: Measure the total area of both feet in contact with the ground by placing
both feet on a graph paper, drawing around the feet (and then counting the
number of squares) to get the area. Then measure the weight of the person
using a scale (W=MG) Finally find the pressure using p= F/A
5. The diagram shows a part of the knee called the patella. The patella has
been removed from a person’s knee.

The patella is a small, irregularly shaped bone that is denser than water. Describe
how to find the mass and the volume of the patella bone.
Ans: Find the mass using a balance ( make sure the balane is zeroed beforehand)
find the volume using the displacement method by fully submerging it in a
measuring cylinder. Measure the initial and final volumes on the measuring
cylinder by reading at eye level and the finding the difference to get the volume
 6. Alternating current is supplied to the transmitter coil. Diagram 2 shows a
gold ring in the soil below the metal detector.

Explain why there is an alternating current in the gold ring.

Ans: Since A.C is supplied to the transmitter coil, a changing magnetic field is
produced around it. The gold ring cuts the field lines from the changing magnetic
field which induces a voltage in the gold ring. (Since direction of magnetic field is
constantly changing, a.c is induced.)
(c) Diagram 3 shows the circuit for the receiver coil.

As a result of the alternating current in the gold ring, there is an

alternating current in the receiving coil.
Explain how an alternating current in the receiving coil causes a sound to be.
emitted from the loudspeaker.
Ans: There is now an alternating current in the loudspeaker which produces a
changing magnetic field around the loudspeaker which interacts with the
magnetic field from the permanent magnet inside the loudspeaker. This produces
a force on the loudspeaker cone. Due to the a.c, the direction of magnetic field is
constantly changing and so does the direction of force produced. Therefore, the
loudspeaker cone vibrates.

7. Describe how the teacher could measure the count rate from a radioactive
source and correct the count rate for background radiation.
Ans:
A car is travelling in a straight line along a road. The car passes a person
standing at the side of the road.

Before passing the person, the driver of the car presses the car’s horn. The
horn
makes a loud sound of constant frequency.
The horn continues to make a sound until after the car has passed the person.
Discuss the differences in the frequencies of the sound heard by
• the driver of the car
• the person at the side of the road
Ans: In relation to the driver, the frequency of the sound does not change as the distance
between the driver and the horn remains constant throughout. (there is no relative movement
between driver and the horn) In relation to the person at the side of the road, the frequency
heard is different to that of the driver as the Doppler Effect applies here. As the car approaches
the person, the wavefronts gets closer together and so the wavelength decreases. The speed of
waves is constant so as v=fλ, frequency is higher. As the car moves away from the person, the
wavefronts become further apart and so the wavelength increases. As v=fA, frequency is lower.

8. A student investigates how the current in a 60 resistor varies with the voltage across the
resistor.
(a) The student has access to this equipment
 12 V battery . .
 ammeter and voltmeter
 60 resistor
 variable resistor
 switch
 connecting wires
Draw a circuit diagram to show how the student could connect this equipment to carry out the investigation .

(b) Describe a suitable method the student could use for this investigation.

Ans: Measure the voltage using the voltmeter and the current using the ammeter Vary the
voltage across the resistor by altering the resistance of the variable resistor. Take repeat
readings and find average at each voltage Switch off current in between readings (Not using full
range of voltage so current doesn't get too high)

(c) (i) Complete the current–voltage graph by drawing a line that shows the

expected results of the investigation.

 (ii) The student repeats their investigation with a 120Ω resistor.

Explain how a current–voltage graph for a 120Ω resistor compares with the current–voltage
graph for the 60Ω resistor.

Ans: The line will still be the same shape and go through the origin However the line will have a
lower gradient, half the gradient to be precise because larger resistance will result in a lower
current in the circuit.

(c) Explain how diagram 1 shows a uniform magnetic field.

Ans: The field lines are straight - evenly spaced – parallel

9. Describe how the teacher could measure the count rate from a radioactive source and
correct the count rate for background radiation.

Ans: Measure the count rate from the source using a Geiger-Muller tube and counter Then, measure
the count rate without the source (to get count rate for background radiation) Measure the
background count several times and calculate mean Subtract the background count from the original
readings

10. Diagram 2 shows the path of the ray of light as it travels through the optical fibre.

Explain the path of the ray of light as it travels through the optical fibre.

Ans: The light ray undergoes total internal reflection as the light ray travels from more dense to
less dense medium and the angle of incidence is greater than the critical angle.
11. Explain which of these stars has the highest surface temperature.

Ans: Rigel because color of star depends on surface temperature. Red (coolest) -> Blue
(hottest).

12. Explain how the atoms exert a pressure on the walls of the container.

Ans: The atoms collide with the walls of the container which exerts a force on the walls.
Pressure is force on an area so the atoms exert pressure.

13. Explain why the pressure of the gas in the container decreases as its temperature
decreases volume of the container does not change.

Ans: As temperature decreases, the average kinetic energy of atoms inside the container
decreases. This causes them to collide with the walls of container with less force and less
frequently.

14. Explain how the balloon reaches terminal velocity. You should use ideas about forces acting
on the balloon in your answer.

Ans: When released, both weight and drag acts on the balloon but weight is greater than drag.
This resultant force causes acceleration. Drag increases with speed and so acceleration
decreases. When acceleration becomes zero, weight = drag at terminal velocity.

15. Describe the difference between nuclear fusion and nuclear fission.

Ans: Fission is the splitting of a nucleus (into two daughter nuclei and releasing neutrons and
energy in the process.) Fusion is the joining of two nuclei (to form a single nucleus)

16. State the name of a detector the teacher could use to detect the radiation from each source.

Ans: Geiger-Muller tube (and counter)

17. The firework makes a sound with constant frequency. As the firework moves upwards,
people on the ground notice that the frequency of the sound they hear changes. This is
called the Doppler effect. Explain how the Doppler effect causes the observed frequency of
sound to change for the people on the ground.

Ans: As the firework moves upwards, the wave fronts spread out behind the firework (towards
the ground) which in turn causes the wavelengths between each sound wave to increase. As
per v=f^, for a constant speed of waves, when wavelength increases, frequency must decrease.
Thus, observed frequency decreases.
18. Describe how the orbit of a comet compares with the orbit of a planet.

Ans: Orbit path of comet is longer Speed of comet varies but speed of planet does not Both
planet and comet orbit a star is at center of planet's orbit but not at center of comet orbit Plane
of comet's orbit is different to plane of planet's orbit. Orbit of a comet is more elliptical (while
orbit of planet is more circular).

19. Sound waves and light waves can have different frequencies and wavelengths. Describe
three other differences between sound waves and light waves. You may draw diagrams to
support your answer.

Ans: Sound wave is longitudinal while light wave is transverse. Light wave is an electromagnetic
wave but sound is not. Light can travel through a vacuum Light travel faster (in air) than sound.
Light slows down in denser medium while sound speeds up

20. Force and velocity are examples of vector quantities.State what is meant by the term vector
quantity.

Ans: A quantity that has both magnitude and direction.

21. State what is meant by the term electric current.

Ans: Rate of flow of charge.

22. State what is meant by the principle of conservation of energy.

Ans: Energy cannot be created or destroyed (it can only be transferred from one store to
another)

23. The actual speed of the car when it has fallen 18 m is lower than the value calculated in (a).

Describe the energy transfers occurring from immediately before the car was released to when
the car has fallen 18 m. Refer to stores and transfers in your answer.

Ans: Immediately after it was dropped, energy is transferred mechanically from its gravitational
store to its kinetic store and does so as it drops. Energy is also transferred to the thermal store
of the car and its surroundings mechanically and by radiation as well.
24. Diagram 1 shows a simple loudspeaker.The coil is connected to an alternating current (a.c.)
supply.

Ans:

Describe how the loudspeaker produces sound.

Ans: When an alternating current is passed through the coil, a changing magnetic field is
produced around the coil. This interacts with the magnetic field from the permanent magnet,
producing a force on the coil. This causes the coil to oscillate which in turn causes the paper
cone to vibrate. The cone forces air to vibrate and thus longitudinal waves are formed.

25. Radon is a radioactive gas that contributes to background radiation.(a) Describe what is
meant by the term background radiation.

Ans: Radiation from sources in the environment. Radiation that exists around us all the time...

26. State what is meant by the term half‐life.

Ans: The time taken for the activity of a sample to halve

27. Explain why the coil starts to rotate when there is a current in the coil.

Ans: When current flows in the coil, a magnetic field is produced around the coil which interacts
with the magnetic field from the permanent magnet. This produces a force on the coil. The
forces act in opposite directions at opposite ends of the coil so it rotates.

28. Give two uses of total internal reflection.

Ans: Optical fibres & Periscope

29. The magnet is made of a magnetically hard material.Describe what is meant by the term magnetically hard.

Ans: Magnetic materials that are difficult to magnetise and difficult to demagnetise They retain their magnetism.
 30. Diagram 3 shows the loudspeakers connected in series to a cell. Diagram 4 shows the
loudspeakers connected in parallel to the same cell.

Comment on how the total resistance of the loudspeakers in diagram 3 compares

with the total resistance of the loudspeakers in diagram 4.

Ans: In diagram 4, cell voltage is no longer shared between the loudspeakers as voltages in parallel
are the same. Therefore, the current through each speaker doubles which means the current from
the power supply is four times higher. As R=V/I, when current increases by four times, total
resistance is a quarter of that from the series case.
31. Diagram 2 shows the boat moving towards an observer.

Ans: This is due to the doppler effect. The wavefronts of waves towards the observer get
squashed together and so the wavelengths between the wavefronts decrease... As v=fλ, for a
constant speed of waves, when wavelength decreases, frequency must increase (from the
observer's perspective)

32. Describe an investigation that could be used to determine the shape of the magnetic field
around a bar magnet.

Ans: Place multiple plotting compasses around the bar magnet Mark down the direction the
arrow is pointing and join the arrows to form a continuous field line Repeat the process for
another line.

33. Explain the shape of the graph from A to C.

34. You should use ideas about forces to help your answer.
35.

36.