Pearson Edexcel International GCSE (9–1) · PHYSICS · Unit
Magnetism and Electromagnetism
293 practice questions
Topics covered
Practice questions
191–200 of 293
Question 191
2 marks · Normal
Answer and see the solution →State the purpose of a soft iron core in a transformer.
Question 192
3 marks · Normal
Answer and see the solution →A transformer is used to produce an output voltage of 48 V from a 240 V a.c. mains supply. The primary coil has 960 turns.
Calculate the number of turns needed on the secondary coil to achieve this output voltage.
Question 193
3 marks · Normal
Answer and see the solution →Explain why transformers cannot be used with a direct current (d.c.) supply.
Question 194
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 195
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 196
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 197
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 198
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 199
1 mark · Easy
Answer and see the solution →State the main purpose of a step-up transformer in the National Grid.
Question 200
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?