Electrical Energy (Cambridge O Level Physics)

• Everyday appliances transfer energy from the mains supply to the appliance
  • For example, a heater will transfer energy electrically to the thermal store of the heating element

• The amount of energy an appliance transfers depends on:
  • The time the appliance is switched on for
  • The power of the appliance

• A 1 kW iron uses the same amount of energy in 1 hour as a 2 kW iron would use in 30 minutes
• A 100 W heater uses the same amount of energy in 30 hours as a 3000 W heater does in 1 hour

Calculating Electrical Energy

• To calculate electrical energy use the equation

• Where:
  • E = energy (joules, J)
  • V = voltage (volts, V)
  • I = current (amps, A)
  • t = time (seconds, s)