College Physics I – Introduction

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Power

Power is the rate at which work is done or energy is transferred over time. It is measured in watts (W), where one watt equals one joule per second.

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Power ($P$) is mathematically defined as $P = \frac{W}{t}$, where $W$ is work and $t$ is time.
The SI unit of power is the watt (W).
In mechanical systems, power can also be calculated using $P = F \cdot v$, where $F$ is force and $v$ is velocity.
For electrical systems, power can be calculated as $P = V \cdot I$, where $V$ is voltage and $I$ is current.
Efficiency of a system can be determined by comparing the output power to the input power.