Pearson Edexcel International GCSE (9–1) · PHYSICS · Unit
Magnetism and Electromagnetism
293 practice questions
Topics covered
Practice questions
101–110 of 154 · Normal
Question 101
4 marks · Normal
Answer and see the solution →The diagram below shows part of a National Grid system used to distribute electricity from a power station to homes.
A simplified National Grid: Power Station, Step-up Transformer, Transmission lines, Step-down Transformer, Homes. (a)[2 marks]Explain why step-up transformers are used after the power station before transmission.
(b)[2 marks]Explain why step-down transformers are used near homes before the electricity enters houses.
Question 102
4 marks · Normal
Answer and see the solution →A step-up transformer in the National Grid has 120 turns on its primary coil and 6,000 turns on its secondary coil. The primary coil is connected to an alternating voltage of 8 V.
(a)[3 marks]Calculate the voltage across the secondary coil.
(b)[1 mark]Explain whether this transformer increases or decreases the current in the secondary coil compared to the primary coil, assuming 100% efficiency.
Question 103
2 marks · Normal
Answer and see the solution →Give two reasons why high voltages are dangerous in the National Grid and must be reduced before entering homes.
Question 104
3 marks · Normal
Answer and see the solution →The table shows information about two types of transformers.
Transformer data Type of transformer Number of primary turns Number of secondary turns Use in National Grid X 300 9000 Y 4000 200 Complete the table by stating the use of each transformer in the National Grid: either 'step-up' or 'step-down'.
Question 105
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 106
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 107
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 108
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 109
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 110
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.