Pearson Edexcel International GCSE (9–1) · PHYSICS · Chapter
Electromagnetism
68 practice questions
Topics covered
Practice questions
41–50 of 68
Question 41
3 marks · Normal
Answer and see the solution →Explain why transformers cannot be used with a direct current (d.c.) supply.
Question 42
4 marks · Normal
Answer and see the solution →The diagram shows a transformer. The secondary coil has 300 turns and produces a voltage of 15 V.
(a)[3 marks]The primary coil has 1200 turns. Calculate the input voltage.
(b)[1 mark]State whether this transformer is step-up or step-down. Give a reason for your answer.
Question 43
1 mark · Normal
Answer and check →Which change would increase the output voltage of a transformer, assuming the input voltage stays the same?
- A.Increase the number of turns on the secondary coil
- B.Decrease the number of turns on the secondary coil
- C.Increase the number of turns on the primary coil
- D.Use d.c. instead of a.c.
Question 44
3 marks · Normal
Answer and see the solution →A student investigates transformers using different numbers of turns on the secondary coil, measuring output voltages. Her results:
Transformer investigation results Turns on Secondary Coil Output Voltage (V) 100 4.0 200 8.1 300 12.0 400 15.8 (a)[1 mark]Describe the relationship between the number of turns on the secondary coil and the output voltage.
(b)[2 marks]Estimate the output voltage if the secondary coil had 500 turns.
Question 45
4 marks · Normal
Answer and see the solution →A transformer is used to power a device that needs 6 V a.c. from the mains (230 V a.c.). The current in the primary coil is 0.10 A. Assume the transformer is 100% efficient.
(a)[3 marks]Calculate the current in the secondary coil.
(b)[1 mark]Explain why the secondary current is greater than the primary current.
Question 46
3 marks · Normal
Answer and see the solution →Describe two reasons why thick, insulated copper wire and a plastic-coated soft iron core are used in transformer construction.
Question 47
1 mark · Easy
Answer and see the solution →State the main purpose of a step-up transformer in the National Grid.
Question 48
2 marks · Easy
Answer and see the solution →Electricity leaves a power station at 25,000 V. A step-up transformer increases the voltage for transmission.
(a)[1 mark]Explain why increasing the voltage is important before transmitting electricity.
(b)[1 mark]What effect does increasing the voltage have on the current in the transmission cables?
Question 49
1 mark · Easy
Answer and check →What is the typical voltage in household sockets after passing through a step-down transformer in the UK?
- A.400,000 V
- B.25,000 V
- C.230 V
- D.9 V
Question 50
1 mark · Easy
Answer and see the solution →Name the type of transformer used to increase voltage for transmission in the National Grid.