Energy and power

When work is done on an object, energy is transferred.

Power is the amount of energy transferred in one second. The more powerful a device is, the more energy it will transfer each second.

Energy transferred = work done, and so we can also say:

Power is the amount of work done in one second.

Power is measured in watts (W).

Calculating power

Power can be calculated using either of these equations:

power = \frac{\text{work done}}{\text{time taken}}power = \frac{\text{energy transferred}}{\text{time taken}}
power in watts (W)power in watts (W)
work done in joules (J)energy transferred in joules (J)
time in seconds (s)time in seconds (s)
Triangle showing work, power and time and their relation to each other.

power = \frac{\text{work done}}{\text{time taken}}

work = power x time taken

time taken = \frac{\text{work done}}{\text{power}}