Electrical Energy (AQA GCSE Physics)

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Energy & Power

  • Everyday appliances transfer energy electrically from the mains to energy stores within the appliance
    • For example, in a heater, energy will be transferred to the thermal store of the heating element, and then to the thermal store of the surroundings 

  • The amount of energy transferred to and from an appliance 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

Examiner Tip

Remember that kilo (k) means 1000, so 1 kW = 1000 W

Energy Transfers in Appliances

  • As charge (electrons) flows around a circuit, energy is transferred from the power source to the various components 
    • As the electrons pass through the power supply, energy is transferred to the electrons
    • As the electrons pass through each component they transfer energy to the component

current-and-energy-nnew

The current transfers energy electrically from the power source to the components

 

  • Some domestic appliances, such as a remote control, transfer energy electrically from the chemical store of the DC cells and batteries
  • Most larger household appliances transfer energy electrically from the AC mains
  • This energy can often be transferred to the kinetic energy store of an electric motor
  • Motors are used in:
    • Vacuum cleaners - to create the suction to suck in dust and dirt off carpets
    • Washing machines (or tumble dryers) - to rotate the drum to wash (or dry) clothes
    • Refrigerators - to compress the refrigerant chemical into a liquid to reduce the temperature

  • Or, the energy can be transferred to the thermal store of heating devices.
  • Heating is used in:
    • Toasters - to toast bread
    • Kettles - to boil hot water
    • Radiators - hot water is pumped from the boiler so the radiator can heat up a room

2-3-2-washing-machine-and-toaster-new

Energy transfers for a washing machine and toaster

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Ashika

Author: Ashika

Expertise: Physics Project Lead

Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.