Efficiency: Energy: Physics: GCSE (9:1)

• Efficiency


  A measure of how good a device is at transferring energy input to useful energy output

  
• Total input energy


  The total amount of energy supplied to a device
• Useful energy output


  The amount of energy that is transferred to useful energy stores
• Wasted energy output

  The amount of energy that is wasted or dissipated to the surroundings
• Efficient device


  A device that wastes very little of its input energy
• Inefficient device


  A device that wastes most of its input energy
• Efficiency = useful output energy transfer ÷ total input energy transfer


  The equation linking efficiency, useful output energy transfer and total input energy transfer
• Efficiency = useful power output ÷ total power input


  The equation linking efficiency, useful power output and total power input
• Percentage efficiency

  Found by multiplying the efficiency by 100
• What is meant by an efficiency greater than 1 or 100%

  More energy is being transferred than is being supplied
• Why can't you have an efficiency greater than 1 or 100%

  This would would break the law of conservation of energy as it would mean that energy is being created
• Reasons devices waste energy

  1) Friction between their moving parts

  2) Heat due to electrical resistance

  3) Unwanted sound or light
• (higher-tier only)

  How to improve efficiency

  Reduce the amount of energy that a device wastes or dissipates to the surroundings
• (higher-tier only)

  Ways to improve efficiency

  1) Lubricate mechanical devices to reduce the friction between moving parts of the machine

  2) Insulate heating devices to reduce the dissipation of thermal energy to the surroundings