Power

In this lesson you will learn what power means in physics, how to calculate it, and how to apply it to compare different devices and situations. Power is part of AQA GCSE Combined Science Trilogy (8464), Section 6.1.

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What Is Power?

Power is the rate of energy transfer — how quickly energy is transferred from one store to another. A more powerful device transfers the same amount of energy in less time.

The Equation

$P = \frac{E}{t}$P=tE​

Where:

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

The Watt

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

A device with a power of 1 W transfers 1 joule of energy every second.

Unit	Equivalent
1 kW	1000 W
1 MW	1,000,000 W

Exam Tip: Always convert kilowatts to watts and minutes to seconds before substituting into the equation.

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Rearranging the Equation

$E = P \times t \qquad t = \frac{E}{P}$E=P×tt=PE​

Worked Example 1

A 2000 W kettle is used for 3 minutes. How much energy does it transfer?