P1.3 Transferring Electrical Energy

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  • Created by: Aisham36
  • Created on: 23-10-15 19:19

Electrical Appliances

  • Electrical appliances - extremely useful, transfer electrical energy to other forms of energy
  • Common electrical appliances: lamps, electrical mixers, speakers, tvs
  • Many electrical appliances transfer energy by heating - useful in things eg. kettles, but energy is often wasted - appliances designed to waste as little energy as possible
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Electrical Power

  • Power - rate at which appliance transfers energy
  • E is energy transferred in kilowatt-hours, kWh
  • P is power in kilowatts, kW
  • t is time in hours, h


  • E is energy transferred in joules, J
  • P is power in watts, W
  • t is time in seconds, s

Power Formula: Work Done (j) / Time Taken (s) = Energy Transferred / Time Taken 

To calculate the cost of mains electricity given the cost per kilowatt-hour.

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The cost of using electricity

Power (W) = energy transferred (J) / time taken (s)

The more powerful a device is, the faster the rate at which it transforms energy.  

Energy transferred (kWh) = power (kW) × time (h)

Total cost = number of units × cost per unit

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