Pearson Edexcel International GCSE (9–1) · PHYSICS · Section
TRANSFORMERS AND NATIONAL GRIDS
17 practice questions
Practice questions
1–9 of 9 · Normal
Question 1
2 marks · Normal
Answer and see the solution →State one purpose of a step-up transformer and one purpose of a step-down transformer in the National Grid.
Question 2
4 marks · Normal
Answer and see the solution →The diagram shows a simplified section of the National Grid.
National Grid: transformers and cables (a)[2 marks]Explain why a step-up transformer is used before electricity enters the transmission line.
(b)[2 marks]Explain why a step-down transformer is needed before electricity is supplied to consumers.
Question 3
3 marks · Normal
Answer and see the solution →A section of the National Grid transmits 2000 kW of electrical power at 400,000 V.
(a)[2 marks]Calculate the current in the transmission line.
(b)[1 mark]Explain why this high voltage is used with reference to energy loss.
Question 4
4 marks · Normal
Answer and see the solution →A transformer used in the National Grid has 200 turns on its primary coil and 4000 turns on its secondary coil. The input voltage is 5 V a.c.
(a)[3 marks]Calculate the voltage across the secondary coil.
(b)[1 mark]State whether this transformer is a step-up or step-down transformer. Give a reason for your answer.
Question 5
4 marks · Normal
Answer and see the solution →Electricity generated at a power station must travel long distances before it reaches homes and factories.
(a)[2 marks]Describe the effect a step-up transformer has on current and voltage when used in the National Grid.
(b)[2 marks]Explain why using step-up transformers is important for reducing energy losses in transmission lines.
Question 6
4 marks · Normal
Answer and see the solution →The table below shows the number of turns and voltage in different parts of a section of the National Grid:
Transformer Primary coil turns Secondary coil turns Primary voltage (V) Secondary voltage (V) Step-up 500 10,000 20 Step-down 2,000 200 220 (a)[2 marks]Calculate the output (secondary) voltage of the step-up transformer.
(b)[2 marks]Calculate the input (primary) voltage of the step-down transformer.
Question 7
4 marks · Normal
Answer and see the solution →A simplified diagram representing a section of the National Grid is shown below.
National Grid section (Power station, Step-up transformer, Transmission line, Step-down transformer, Factory) (a)[2 marks]On the diagram, draw and label the sections where the voltage is highest and lowest.
(b)[2 marks]Explain, using the diagram, why a step-down transformer is used before electricity enters a factory.
Question 8
3 marks · Normal
Answer and see the solution →Explain what would happen if only step-up transformers (no step-down transformers) were used in the National Grid. Give two consequences for users and one for the safety of the system.
Question 9
1 mark · Normal
Answer and check →Which statement about transformers in the National Grid is correct?
- A.Step-up transformers increase voltage and reduce current for transmission.
- B.Step-down transformers increase voltage before transmission.
- C.Step-up transformers are only used in homes.
- D.Step-down transformers are used to increase voltage to dangerous levels.