Electrical energy itself is not a useful form of energy for us, but it supplies energy to our appliances which transform it into other forms of energy which are useful.
An electric fire, a cooker, a toaster and an electric kettle all convert electrical energy into heat energy.
The power of an appliance is the rate at which energy is transferred.
Appliances in the home have their power ratings stated on their base plates:
Typical power ratings include:
|Appliance||Power rating \[(W)\]|
|Microwave oven (cooking power of \[800\])||1000|
Calculate the power rating of a hair dryer that is used for 2 minutes and uses 100 kilojoules of energy.
To calculate the power rating you need to take the following steps:
\[power = energy \div time\]
\[= 100000 \div (2 \times 60)\]
\[= 830 watts\,(830 W)\]
\[Energy = 830 W\]