Power (Oxford AQA IGCSE Combined Science Double Award)

Revision Note

Written by: Leander Oates

Reviewed by: Caroline Carroll

Machines, such as car engines, transfer energy from one energy store to another constantly over a period of time
The rate of this energy transfer, or the rate of work done, is called power
Time is an important consideration when it comes to power
Two cars transfer the same amount of energy, or do the same amount of work to accelerate over a distance
If one car has more power, it will transfer that energy, or do that work, in a shorter amount of time

Energy transferred per unit time

$P = \frac{E}{t}$

Where:
- P = power in watts (W)
- E = energy transferred in joules (J)
- t = time in seconds (s)
Energy transferred is equivalent to work done

energy transferred = work done

$P = \frac{W}{t}$

Where:
- P = power in watts (W)
- W = work done in joules (J)
- t = time in seconds (s)

Calculate the energy transferred when an iron with a power rating of 2000 W is used for 5 minutes.

Answer:

Step 1: List the known values

Step 2: Write down the relevant equation

$P = \frac{E}{t}$

Step 3: Rearrange for energy transferred, ΔE

$E = P \times t$

Step 4: Substitute in the known values

$E = 2000 \times 300$

$E = 600 000 J$

Since work done = force × distance, work done provides a mathematical link between forces and energy. This is commonly used in exam questions.

Last updated: 3 April 2024

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