A student uses a laptop computer for several hours each day. Describe how energy is usefully transferred by the laptop and explain how the waste energy transfer from the laptop could be reduced.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A laptop computer has a power rating of 45 W. When in use, it becomes warm to the touch.
Model answer (4 marks)
The laptop converts electrical energy from the battery into useful work – light from the screen and sound from the speakers. The remaining electrical energy is lost as heat, which is transferred to the surrounding air.
The waste heat can be reduced by lubricating the moving parts such as the cooling fan, which lowers friction and therefore less energy is turned into heat. Heat can also be removed more efficiently by improving the design of the components or by adding thermal insulation to slow the rate of heat transfer to the environment.
The waste heat can be reduced by lubricating the moving parts such as the cooling fan, which lowers friction and therefore less energy is turned into heat. Heat can also be removed more efficiently by improving the design of the components or by adding thermal insulation to slow the rate of heat transfer to the environment.
Examiner tips
- Use the terms "electrical energy", "light", "sound" for the useful transfer; mention "heat" for waste. Show the two ways to reduce waste: lubrication and better design/insulation. Keep the answer concise to fit the 4‑mark structure.
Common mistakes
- Confusing the laptop’s power rating with the amount of useful energy; describing only the battery capacity. Failing to mention the heat transfer to the surroundings or giving irrelevant ways to reduce waste such as turning the laptop off.
Mark scheme (4 marks)
- The useful energy transfer is electrical energy transferred to light (screen) and/or sound (speakers)
- The waste energy transfer is energy dissipated as heat/thermal energy to the surroundings
- Lubrication of moving parts (e.g. the fan) reduces friction, so less energy is dissipated as heat
- Thermal insulation could reduce the rate of heat transfer from the laptop to the surroundings, OR improving component design reduces waste energy transfer, increasing efficiency
Key terms in this question
Related
- All WJEC GCSE Physics (Wales) revision notes →
- How to answer a "Describe and Explain" question →
- Decode the mark scheme abbreviations →
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