Improving Efficiency (Edexcel GCSE Physics: Combined Science)

Higher Tier Only

• The efficiency of a device can be improved by reducing wasted energy transfers
• 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 between the moving parts of the machinery
• This results in unwanted energy transfers by heating to the machinery and the surroundings
• Friction can be reduced by:
  • Adding bearings to prevent components from directly rubbing together
  • Lubricating parts

Lubricating parts of a bicycle to reduce friction

Reducing Electrical Resistance

• In electric circuits there is resistance as current flows through the wires and components
• This results in unwanted energy transfers by heating to the wires, components and the surroundings
• Resistance can be reduced by:
  • Using components with lower resistance
  • Reducing the current 

Reducing Air Resistance

• Air resistance causes a frictional force between the moving object and the air that opposes its motion
• This results in unwanted energy transfers by heating to the object and the surroundings
• Air resistance 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

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

Reducing Noise

• Sound is often created by moving parts of machinery
• This results in unwanted energy transfers by heating to the surroundings as sound waves cause the particles in the air and nearby objects to vibrate
• Sound can be reduced by:
  • Tightening loose parts to reduce vibration
  • Lubricating parts