GCSE Standard Questions: The Generator
(Electromagnetic Induction)
Q2. The diagram shows some parts of a torch which works without batteries. The coil is part of a complete circuit with the LED (light-emitting diode). You have to shake the torch for a short time and then it is ready to use.
(a) Arrange the letters, A, B, C, D and E, in the correct order to explain how shaking the torch produces an electric current.
A |
An electric current is induced in the circuit. |
B |
The magnetic field cuts through the coil. |
C |
The magnet moves in and out of the coil. |
D |
A potential difference (p.d.) is induced across the ends of the coil. |
E |
The torch is shaken to and fro |
(2 marks)
(b) Give two changes which you would make to the design of the torch to increase the size of the induced potential difference.
(2 marks)
(c) A few minutes after shaking, the LED gets dimmer and then stops giving out light. A student tests the torch. She shakes it for a period of time. Then she switches it on and times how long the light lasts. These are her results.
Period of time torch is shaken measured in seconds |
How long the light lasts measured in seconds |
30 |
168 |
60 |
312 |
90 |
420 |
120 |
546 |
150 |
654 |
(i) What conclusion can the student come to on the basis of these results?
(1 mark)
(ii) The student's friend says that the results are not reliable. Her friend is correct. Give two reasons why.
(2 marks)
(Total 7 marks)
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