# Power (physics)

In physics, **power** is the amount of energy transferred or converted per unit time. In the International System of Units, the unit of power is the watt, equal to one joule per second. In older works, power is sometimes called *activity*.[1][2][3] Power is a scalar quantity.

Power | |
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Common symbols | P |

SI unit | watt (W) |

In SI base units | kg⋅m^{2}⋅s^{−3} |

Derivations from other quantities | |

Dimension |

Part of a series on |

Classical mechanics |
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Power is related to other quantities; for example, the power involved in moving a ground vehicle is the product of the aerodynamic drag plus traction force on the wheels, and the velocity of the vehicle. The output power of a motor is the product of the torque that the motor generates and the angular velocity of its output shaft. Likewise, the power dissipated in an electrical element of a circuit is the product of the current flowing through the element and of the voltage across the element.[4][5]