Power

This lesson covers power and how to calculate it using $P = \frac{E}{t}$P=tE​ and $P = \frac{W}{t}$P=tW​, as required by the Edexcel GCSE Combined Science specification (1SC0). Understanding power allows you to compare how quickly different devices transfer energy.

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What Is Power?

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

• A powerful device transfers energy quickly.
• A less powerful device transfers the same amount of energy, but more slowly.

The unit of power is the watt (W).

$1 \text{ W} = 1 \text{ J/s}$1 W=1 J/s

One watt means one joule of energy is transferred per second.

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The Power Equations

There are two versions of the power equation:

$P = \frac{E}{t} \qquad \text{and} \qquad P = \frac{W}{t}$P=tE​andP=tW​

where:

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

Both equations say the same thing — power is energy (or work done) divided by time.