Electrical Energy

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Energy is transferred=Power X Time

  • The total energy transferred by an appliance can be found using this equation:
  • Energy Transferred (in joules)=Power (in W) X Time (in s)
  • Example: How much energy is transferred by a 2500 W kettle left on for 300 s?
  • Answer: Energy=Power X Time = 2500 W X 300 s=750 000 J

Kilowatt-hours (kWh) are "UNITS" of energy

  • Energy is usually measured in joules J
  • But one joule is a tiny amount of electrical energy
  • So your electricity meter records how much energy you use in units of kilowatt-hours, or kWh
  • A kilowatt-hour


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