GCSE Standard Questions: The Generator

Q1. The diagram shows the inside of an oil pipeline and a student's design for a meter to measure the flow of oil.

  • As oil flows through the pipeline, the oil rotates a turbine wheel.
  • Above the turbine wheel is a coil of wire connected to a data logger.
  • There is a magnet in the rim of the turbine wheel. The turbine wheel spins and this induces a varying potential difference (p.d.) across the ends of the coil.
  • This varying p.d. is recorded by the data logger.

(a) Complete the sentence below by suggesting a word for dotted space: The faster the oil flows through the pipeline, the ...?... the maximum p.d. across the coil.

(1 mark)

(b) Explain why a varying p.d. is induced across the coil even when the rate of flow of oil remains constant.

(3 marks)

(c) Suggest two changes to the design of the meter which would increase the maximum p.d. across the coil for the same flow of oil.

(2 marks)

(Total 6 marks)

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)

Q3. The diagram below shows a generator. When the coil is rotated around the axle, a current is produced and the lamp lights up.

(a) Explain the purpose of the slip rings and brushes.

(2 marks)

(b) Explain how this generator gives an a.c. rather than a d.c. output.

(2 marks)

(c) In this design, the generator effect occurs because the coil rotates in a magnetic field. How else can a generator effect occur?

(1 mark)

(Total 5 marks)

Q4. The diagram shows a student's design for a simple wind speed gauge.

(a) Explain why the wind causes the a.c. voltmeter to give a reading. The explanation has been started for you.

The wind causes the plastic cups to turn. This causes the spindle and magnet to turn..............

(2 marks)

(b) The gauge is not sensitive enough to measure light winds. Suggest one way that the design can be modified to make the gauge more sensitive.

(1 mark)

(Total 3 marks)