Physics P1 Electrical Energy


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  • Created by: Phoebe
  • Created on: 08-06-12 16:07

3.1-3 Electrical Appliances

  • An electrical appliance is designed for one particular purpose and should waste as little energy as possible
  • The power of an appliance is the rate at which it transfers energy
  • Power=Energy/Time
  • Energy=Power x Time
  • Time=Energy/Power
  • Efficiency=Useful power out/Total power in (x100%)
  • The kilowatt-hour is the energy supplied to a 1kW appliance in 1 hour
  • Total cost=number of kWh x cost per kWh
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3.4 Cost effectiveness matters

  • Cost effectiveness means getting the best value for money

To compare the cost effectiveness of different appliances we must consider a number of different costs, including:

  • purchase cost
  • installation cost
  • running costs
  • maintenance costs
  • environmental costs
  • possible interest charged if a loan has been taken

The payback time is the time it takes for an appliance to pay for itself in terms of energy saving e.g.

  • Loft insulation costs £600. It saves £80 per year. How long is the payback time? 600/80=7.5 years
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