Power & Domestic Electric Appliances (AQA GCSE Combined Science: Synergy: Physical Sciences): Revision Note

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

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

• 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