Pearson Edexcel International GCSE (9–1) · PHYSICS · Chapter
Electromagnetism
68 practice questions
Topics covered
Practice questions
61–68 of 68
Question 61
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 62
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 63
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 64
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 65
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 66
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 67
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 68
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.