Electrical Power
Power in an electrical circuit.
Formula
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Example
A 240 V appliance drawing 5 A uses P = 240·5 = 1200 W.
How it works
Electrical power is the rate at which an electric circuit transfers energy. Since voltage is the energy given to each unit of charge and current is the amount of charge flowing each second, multiplying them gives energy per second, which is power. So P = VI tells you how quickly an appliance, component, or circuit is using or delivering electrical energy.
When to use it
Use this formula when you know the voltage across a device and the current through it and want to find its power rating or energy use rate. It is commonly used for appliances, batteries, lamps, motors, and simple circuit calculations.
Worked example, step by step
A small fan has a voltage of 12 V and draws a current of 0.8 A. P = VI P = 12 × 0.8 P = 9.6 W So the fan uses 9.6 watts of electrical power.
Common mistakes to avoid
- mixing up volts and watts and using the formula with the wrong units
- forgetting to multiply voltage by current, or adding them instead
- using the formula without checking that the current is in amperes and the voltage is in volts
Did You Know?
Power lost in a wire grows with the square of current — the reason for high-voltage transmission.
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