Electrical Power

This lesson covers electrical power and the equations used to calculate it, as required by the Edexcel GCSE Combined Science specification (1SC0). You will learn to use $P = IV$P=IV, $P = I^2R$P=I2R and $P = \frac{V^2}{R}$P=RV2​ and apply them to compare electrical devices.

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What Is Electrical Power?

Power is the rate at which energy is transferred (or the rate at which work is done).

$P = \frac{E}{t}$P=tE​

where:

• P = power in watts (W)
• E = energy transferred in joules (J)
• t = time in seconds (s)

Quantity	Unit	Equivalent
Power	Watt (W)	1 W = 1 J/s
	Kilowatt (kW)	1 kW = 1000 W

A 60 W lamp transfers 60 joules of energy every second.

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The Three Power Equations

For electrical circuits, power can be calculated using three related equations.

Equation 1: P = IV

$P = IV$P=IV

where:

• P = power in watts (W)
• I = current in amperes (A)
• V = potential difference in volts (V)