Power (physics)

2017-01-16T16:49:09Z

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In [[physics]], '''power''' (symbol: ''P'') is how fast [[Work (physics)|work]] is done or [[energy]] is given from one thing to another. In the [[SI]] system of measurement, power is measured in [[watt]]s (symbol: W).

It may take a certain amount of work to make a change in the world, such as lifting a heavy weight to a higher level. It makes no difference if the weight is lifted slowly or quickly. The same amount of work will have been performed. The difference between a slow lift and a quick lift is that a quick lift requires more power. This means the work can be done in a shorter time if there is more power available.

As a rate of change of work done or the energy of a subsystem, power is:

:<math>P=\frac{W}{t}</math>

where
:''P'' is power,
:''W'' is [[Work (physics)|work]], and
:''t'' is [[time]].

Power is also equal to force times velocity (or speed).

== Power in optics ==

In [[optics]], or [[radiometry]], the term ''power'' sometimes refers to [[radiant flux]]. This is the average rate of energy transport by electromagnetic radiation, measured in [[watt]]s. But the term "power" is also used to express the ability of a [[Lens (optics)|lens]] or other optical device to [[:wikt:focus|focus]] light. It is measured in [[dioptre]]s (inverse [[metre]]s), and is equal to one over the [[focal length]] of the optical device.

[[Category:Physical quantity]]
[[Category:Basic physics ideas]]

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Power (physics)