AQA GCSE Physics

Revision Notes

1.1.16 Improving Efficiency

Higher Tier Only

Improving Efficiency

  • The efficiency of a device can be improved by reducing the amount of unwanted energy that is produced (usually heat, light or sound)
  • Machines waste energy due to:
    • Friction between their moving parts
    • Air resistance
    • Electrical resistance
    • Noise

Reducing Friction

  • In a mechanical system, for example, there is often friction, which can result in unwanted heat being produced
  • This friction can be reduced by:
    • Adding bearings to prevent components from directly rubbing together
    • Lubricating parts

Reducing Electrical Resistance

  • Electrical systems can also produce heat due to the presence of resistance
  • High resistance within electrical components can cause them to become very hot
  • Heat loss can be reduced by:
    • Using components with lower resistance
    • Lowering the current to reduce the amount of heat produced

Reducing Air Resistance

  • Air resistance causes a force between the moving object and the air that opposes its motion
  • Heat is produced as a result and is lost to the surroundings
  • Heat loss can be reduced by:
    • Streamlining the shapes of moving objects
  • For example, a racing cyclist adopts a more streamlined posture to reduce the effects of air resistance
    • Also, the bicycle, clothing and helmet are designed to allow them to go as fast as possible

Racing cyclist, downloadable AS & A Level Physics revision notes

Many factors such as posture, clothes and bicycle shape must be considered when trying to reduce air resistance

Reducing Noise

  • Sound created by machinery causes energy transfer to the surroundings
  • This noise can be reduced by:
    • Tightening loose parts to reduce vibration
    • Lubricating parts

Exam Tip

When answering questions about improving efficiency, it is helpful to identify the useful energy output and the wasted energy output(s). Remember, the efficiency of a device is improved by increasing the USEFUL energy output of the device.

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