Pearson Edexcel International GCSE (9–1) · PHYSICS · Unit
Magnetism and Electromagnetism
293 practice questions
Topics covered
Practice questions
211–220 of 293
Question 211
4 marks · Normal
Answer and see the solution →Electricity is transmitted over long distances from power stations to towns.
Explain in detail, using scientific ideas about current and voltage, how transformers help to reduce energy loss during this transmission.
(a)[2 marks]Describe what happens to the current in the transmission wires when a step-up transformer increases the voltage.
(b)[2 marks]Explain why this change in current is important for energy loss.
Question 212
4 marks · Normal
Answer and see the solution →A village receives electricity from a National Grid. The voltage on the transmission cables is 132,000 V.
(a)[2 marks]Give two reasons why a step-down transformer is needed before the electricity enters homes.
(b)[2 marks]The step-down transformer reduces the voltage to 230 V. Explain what happens to the current in the secondary coil compared to the primary coil, assuming no energy is lost.
Question 213
3 marks · Normal
Answer and see the solution →Explain, using scientific ideas, why it would be inefficient and impractical to transmit electricity at low voltage but high current.
Question 214
4 marks · Normal
Answer and see the solution →Draw a labelled diagram of a transformer. Include the following labels: primary coil, secondary coil, soft iron core, input (AC supply), and output.
Question 215
5 marks · Easy
Answer and see the solution →A transformer is used in a small wind turbine system to supply electricity from the generator to a farmhouse.
(a)[2 marks]Describe how a transformer works, including its main parts.
(b)[1 mark]State why an alternating current (a.c.) is necessary for a transformer to work.
(c)[2 marks]Explain how using a transformer in a National Grid system helps reduce energy losses during transmission.
Question 216
4 marks · Easy
Answer and see the solution →A coil of wire is connected to a sensitive ammeter as shown. A bar magnet is moved into and out of the coil.
Magnet and coil apparatus. (a)[1 mark]State what effect moving the magnet into the coil has on the ammeter reading.
(b)[2 marks]Explain why a current is induced in the coil when the magnet is moved.
(c)[1 mark]State two changes you could make to increase the size of the induced current.
Question 217
6 marks · Normal
Answer and see the solution →An electric motor uses electromagnets and is connected to the National Grid.
(a)[3 marks]Describe how an electric current in a coil produces a force, and explain how this makes the coil rotate in an electric motor.
(b)[3 marks]Transformers are used in the National Grid. Explain why step-up transformers are used to transmit electricity from power stations.
Question 218
5 marks · Normal
Answer and see the solution →A coil of wire is moved quickly through a magnetic field in a generator, which is connected to a step-down transformer.
(a)[2 marks]Describe how electromagnetic induction occurs in the coil when it is moved through the magnetic field.
(b)[1 mark]Explain how changing the speed of movement of the coil affects the size of the induced voltage.
(c)[2 marks]A step-down transformer connected to the generator has 3000 turns on its primary coil and 600 turns on its secondary coil. The input voltage to the primary is 240 V a.c. Calculate the output voltage of the secondary coil.
Question 219
5 marks · Normal
Answer and see the solution →A solenoid is used as an electromagnet and is part of a moving-coil loudspeaker. The speaker is powered by an alternating current produced by a generator.
(a)[2 marks]Describe the magnetic field pattern produced around a solenoid when current flows through it.
(b)[2 marks]Explain why the core of the solenoid in an electromagnet should be made from iron and not steel.
(c)[1 mark]Explain briefly how the movement of a generator's coil produces an alternating current to power the speaker.
Question 220
5 marks · Normal
Answer and see the solution →A power station uses large generators and transformers to supply electrical energy to homes.
(a)[2 marks]Explain why the electricity generated by the power station must pass through step-up transformers before long-distance transmission.
(b)[2 marks]A step-up transformer has 120 turns on its primary coil and 2,880 turns on its secondary. If the input voltage is 11,000 V a.c., calculate the output voltage.
(c)[1 mark]Describe one danger associated with transmitting electricity at high voltages.