Explain why the power rating of an appliance is important when considering how much energy it transfers.

AQA GCSE Physics (8463) — 4.2.4 Energy transfers in everyday appliances · Explain · 4 marks · View as Markdown

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

A tumble dryer has a power rating of 2500 W. A phone charger has a power rating of 5 W.

Model answer (4 marks)

Power rating tells how much energy an appliance transfers each second. A higher power rating means more energy is moved in the same time.

Energy transferred is the product of power and time (E = P × t). Therefore, for a given operating time, an appliance with a higher power rating will transfer more energy.

Because more energy is used, the appliance will cost more to run and draw more electrical energy from the supply.

Examiner tips

  • Use the formula E = P × t to link power and energy.
  • Show that higher power gives more energy for the same time.
  • Mention cost/energy consumption as a consequence.
  • Keep the answer concise and use the exact terminology.

Mark scheme (4 marks)

  1. Power rating shows the energy transferred per second (by the appliance)
  2. The greater the power rating, the more energy is transferred (in a given time)
  3. Energy transferred depends on both power rating and time (E = P × t)
  4. An appliance with a higher power rating will transfer more energy (and therefore cost more to run / use more electrical energy from the supply) for the same amount of time

Key terms in this question

power rating

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