A student notices that the motor in an old electric fan gets very hot during use. Explain how the manufacturer could improve the efficiency of the fan motor, and describe the effect this would have on the waste energy transfer.

WJEC GCSE Physics (Wales) — 1.3 Making use of energy · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

An old electric fan motor transfers electrical energy when running. Much of this energy is wasted as heat in the motor.

Model answer (4 marks)

Lubrication of the moving parts reduces friction in the motor.

Reducing friction means less electrical energy is lost as heat.

A greater proportion of the electrical energy input is then usefully transferred to the kinetic energy of the fan blades.

The waste energy transfer is reduced, so the motor produces less heat.

Examiner tips

  • Use the exact terms ‘lubrication’, ‘friction’, ‘waste energy’, ‘heat’ and ‘kinetic energy’ as the mark scheme does.
  • Show the cause–effect chain: lubrication → less friction → less heat → more useful energy.
  • Keep each point short and to the point to fit the 4‑mark answer.

Mark scheme (4 marks)

  1. Lubrication (of moving parts) reduces friction in the motor
  2. Reducing friction means less energy is dissipated/wasted as heat
  3. A greater proportion of the electrical energy input is usefully transferred (to kinetic energy of the fan blades)
  4. The waste energy transfer is reduced / the motor produces less heat

Key terms in this question

efficiency · waste energy transfer

Related

More Making use of energy questions

▶ Try answering this question with AI marking (free) →