AQA - GCSE Science: Double Award H - Paper 3 - Friday 16 June 2000 1.30 – 3.00pm
1. Microwaves are used to cook food.
(a) Explain how microwaves cook food in a microwave oven.
(2)
(b) Explain how microwaves escaping from the oven can harm you.
CHECK YOUR ANSWERS
2 The diagram shows atoms of carbon- 12 and carbon- 14.
The symbols represent the particles found in atoms
Use words from the list to complete the sentences.
electrons isotope molecule neutrons
nucleus protons orbit
Particles with the symbol in the diagram are called
Particles with the symbol and together make up the . of an atom.
Carbon-14 has more . than carbon-12.
(3)
3 (a) The diagrams show the readings on a domestic electricity meter in February and May.
(i) Calculate the number of Units of electricity used between the two meter readings.
Number of Units
(ii) One Unit costs 8 p.
Calculate the cost of the energy used between the two meter readings.
Cost
(b) Use the equation to calculate the number of Units used by a 2000W electric fire in 3 hours
Number of Units used .
(c) A lamp is connected to a 230V supply. The current flowing through the lamp is 0.26A.
(i) Calculate the power of the lamp.
Power
......................W(2)
(ii) Calculate the amount of electrical charge which flows through the lamp in 30 hours
Charge
......................... C (3)
4 The diagram shows the position of a heater and a window on the outside wall of a room.
The heater is switched on and warms the air. The warm air transfers energy round the room.
(a) (i) On the diagram, use arrows to show the path taken by the air which is warmed by
the heater.
(ii) Name this type of energy transfer to the room .
(1)
(iii) Explain, as fully as you can, why the warmed air moves round the room in this way.
(4)
(b) Energy transfer from the room to the outside can be reduced by fixing a sheet of metal foil to the wall behind the heater.
Explain why the metal foil reduces energy transfer to the outside.
(c) Give two other ways of reducing the transfer of thermal (heat) energy from the room to the outside.
5. During nuclear fission in a nuclear reactor, atoms of uranium‑235 are bombarded by neutrons.
(a) Describe, as fully as you can, what happens in the reactor as a result of this bombardment.
(b) When the uranium‑235 is used up, the waste material from the reactor must be stored for a long time.
Explain, as fully as you can, why the waste material must be stored for a long time.
(c) A radioactive isotope has a half-life of 80 years.
Calculate the fraction of the isotope which would decay in 240 years.
6. The diagram shows a steel block in three different positions, A, B and C on a bench.
(a) (i) Calculate the area of the steel block in contact with the bench when in position C.
Area cm2
(ii) The weight of the steel block is 15 N. Calculate the pressure exerted on the bench by the steel block when in position C.
Pressure .N/cm2
(b) In which position, A, B or C does the steel block exert the greatest pressure on the bench?
Position
Explain your answer
7 A plastic ruler is rubbed with a duster.
(a) The ruler becomes negatively charged.
(i) Explain how this happens.
(ii) State what charge is left on the duster. (4)
(b) The diagram shows how electrical charges are used in paint spraying of car doors.
As they leave the nozzle the paint droplets are given a positive charge.
The car door is given a negative charge.
(i) The charged paint droplets spread out much more than uncharged paint droplets.
Explain why this happens.
(ii) Giving the car door a negative charge improves the paint spraying process.
(c) (i) Give one situation in which static electricity is dangerous.
(ii) Explain how the electric charge, in this situation, can be discharged safely.
8 A student carries out an experiment with a steel ball bearing and a tube of thick oil.
The diagram shows the apparatus used.
The student releases the ball bearing and it falls through the oil.
(a) Two forces X and Y act on the ball bearing as it falls through the oil. This is shown on the diagram.
Name force X
Name force Y
(b) The graph shows how the speed of the ball bearing changes as it falls through the oil.
(i) What is happening to the speed of the ball bearing between points A and B? (1)
Explain, in terms of forces X and Y, why this happens
(ii) What is happening to the speed of the ball bearing between points C and D?
Explain, in terms of forces X and Y, why this happens.
(c) Use the graph to help you to calculate the distance travelled by the ball bearing between points C and D.
Distance ......................................................... cm
9 The diagram shows how electrical energy is transmitted from a power station to the consumer.
(a) (i) What is the purpose of Transformer A?
(ii) Why is it necessary to have Transformer B between the power lines and the consumer?
(b) Explain, as fully as you can, why electricity is transmitted at very high voltages through the power lines.
(c) Explain why these transformers only work using alternating current (a.c.).
10 (a) Complete the following sentences about waves.
Waves travelling across the surface of water are waves.
The disturbance in the water isthe direction
in which the wave is travelling.
Sound waves in air are waves.
The disturbance of the air is the direction in which the wave is travelling.
waves can travel through a vacuum.
When a wave moves through a gap it spreads out. This is called
(6)
(b) The diagram shows apparatus used to find the position of a flaw in a metal casting. The cathode ray oscilloscope is producing a visual display to show how the ultrasonic waves are partly reflected at different boundaries.
Explain, as fully as you can, how ultrasonic waves are used to find the position of the flaw in the metal casting.
(c) The diagram shows a TV and radio transmitter and a house, separated by a hill.
(i) Explain why the radio waves can be received at the house.
(ii) Suggest one reason why the TV waves cannot be received at the house.
11 (a) Describe, in as much detail as you can, the orbit of a planet in the Solar System.
(b) Give two different uses of artificial satellites which orbit the Earth.
(c) Comets are rarely seen. Explain this in terms of their orbits.