A mobile phone charger and an electric shower both transfer electrical energy. Describe the useful energy transfers that take place in each appliance and explain which appliance has a greater power rating.

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

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

Model answer (4 marks)

A mobile phone charger transfers electrical energy into chemical (potential) energy stored in the battery.
An electric shower transfers electrical energy into thermal energy, heating the water.
The electric shower has a greater power rating than the mobile phone charger.
A greater power rating means more energy is transferred per second; heating a large volume of water requires much more energy per second than charging a phone battery.

Examiner tips

  • Use the exact terms "chemical (potential) energy" and "thermal energy". State the power comparison clearly. Explain why the shower needs more power – link to energy per second and volume of water.

Common mistakes

  • Using vague terms like "useful energy" instead of the specific energy types. Failing to mention that the shower’s power is greater. Not explaining that power is energy per second or why heating water needs more power.

Mark scheme (4 marks)

  1. The mobile phone charger transfers electrical energy to chemical (potential) energy (stored in the battery).
  2. The electric shower transfers electrical energy to thermal energy (to heat the water).
  3. The electric shower has a greater power rating (than the mobile phone charger).
  4. A greater power rating means more energy is transferred per second, and heating a large volume of water requires much more energy per second than charging a phone battery.

Key terms in this question

power rating · electrical energy

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