Watt

The watt (symbol: W) is the SI unit of power. It is named in honour of the physicist James Watt (1736–1819).

Definition

The watt is the rate a source of energy uses or produces one joule during one second, so the same quantity may be referred to as a joule per second, with the symbol J/s. It can also be written as kg·m²·s⁻³.

It is equivalent to one volt ampere (1 V·A) or 1/746 of a horsepower. The power of a light bulb is measured in watts.

1000 watts is called a kilowatt, written as kW. In many countries, electric bills are based on how many kilowatt-hours are being used.

1000000 watts is called a megawatt, written as MW. This is used to describe how much electricity is needed by a large town.