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Electric power

Electric power is the energy converted in a component each second, for example into heat in a resistor or light in a bulb. Combined with Ohm's law, the power can be written in three equivalent ways, useful depending on which quantities you know.

P = UI

electric power

P = RI^2

power in terms of current and resistance

P = \dfrac{U^2}{R}

power in terms of voltage and resistance

Symbols

$P$	power	W
$U$	voltage	V
$I$	current	A

Example

A heater has $R = 24$ Ω and is connected to $U = 230$ V. The power is $P = U^2/R = 230^2/24 \approx 2204$ W.

Pick the form of

P

that matches the quantities you know – they all give the same answer.

Practise electricity for free →

← Ohm's law · Series connection →

Part of Foundations of Physics: Electricity.