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GCSE Standard Questions: The Generator

(Electromagnetic Induction)

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.

any two from:

  • to (electrically) connect or to complete the circuit or to allow a current / charge to flow
  • to allow a connection between stationary and moving parts
  • without tangling the wires

(2 marks MAX)

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

The direction of the (induced) current is reversed / alternates every half turn Accept (induced) p.d. across the coil instead of current but do not accept p.d. in the coil.

This is an example of how you have to be careful with electrical terms - current flows in a wire because there is a p.d. across the ends of it - p.d. is like a difference in electrical height!

(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?

You can induce a current in a wire (get the generator effect) by rotating / moving a magnetic field / magnet relative to a coil

(1 mark)

(Total 5 marks)