Last edited 17 Oct 2018


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In physics, power is the rate at which physical work of some kind is done, or the amount of energy that is transferred per unit of time. It involves a physical system changing over a specified time.

The equation for power is often written as:

Power = work/time

According to the International System of Units (SI), the unit of power is the joule per second (J/s), which is also known as a ‘watt’ (named after James Watt, the inventor of the steam engine condenser). Another measurement is horsepower, in which power is compared to the power of a notional horse.

Mechanical power is typically described as the time derivative of work, and is the combination of forces and movement.

Power can also relate to electricity; specifically, electrical power is the rate per unit time at which an electric circuit transfers electrical energy. The term 'power generation' describes the process of generating electrical power, and electric generators, or sources such as electric batteries, are commonly used to provide electrical power.

Designing Buildings Wiki has a range of articles relating to power, including: