Power Ratings (AQA GCSE Combined Science: Trilogy: Physics): Revision Note

Power Ratings

• The power of an appliance is the amount of energy it transfers by electrical working every second

• Every electrical appliance has a power rating which tells you how much energy it transfers each second when it is working

• The power rating for domestic electrical appliances is normally given on a label. This will include:

  • The potential difference required to make the device work (e.g. 230 V in the UK)

  • The frequency of the supply (e.g. 50 Hz in the UK)

  • The power rating in watts (this varies for each device)

• The higher the power rating, the faster the energy is transferred

  • For example, a 2000 W kettle means the kettle transfers 2000 J of energy per second

  • A higher power rating means more energy is transferred each second, so more energy is transferred in the same time

  • This energy comes from a store, for example the chemical store of a battery or the supply from the mains, and is transferred to the kinetic store of a motor or to the thermal store of a heater

• The different power ratings of various household appliances are listed in the table below as examples:

• Care must be taken not to plug an appliance into a mains supply that has a voltage much higher than stated on the label, for example in another country that has a higher mains voltage

  • This could make the appliance overheat, catch fire or be damaged

Mains electric appliances, such as this kettle, are fitted with labels that list important information such as the power and voltage of the appliance