### GCSE Physics

Energy
Forces
Forces and Motion
Waves in Matter
Electricity
Magnetism and Electromagnetism
Particle Model of Matter
Atomic Structure
Space Physics

# Power and Work Done

## Power

Power is the rate at which energy is transferred, as shown in the equation below.

• P = Power in watts (W)
• E = Energy transferred in joules (J)
• t = Time taken to transfer that energy in seconds (s)

Note: 1 watt = 1 Joule per second

## Work Done

Another definition of power is the rate at which work is done, as shown in the equation below.

This equation is used when a force is used to move an object over a given distance. For example, if you push a car, the energy expended is the work done.

Both energy transferred and work done are measured in joules.

There are two main types of work done:

1. Mechanical

2. Electrical

### Mechanical work

Mechanical work is done when a force moves an object, like kicking a ball.

In this scenario, the chemical energy stored in your leg transfers to kinetic energy as the ball travels a distance.

### Electrical work

Electrical work involves moving electrons, which produces a current. It represents the energy needed to overcome the resistance in a circuit’s wiring.

### Calculating work done

Below is the equation relating work done to the force applied and the distance travelled in the direction of that force.

• W = Work done in joules (J)
• F = Force applied in newtons (N)
• D = Distance travelled in metres (m)

## Example

A child applies 5 N to move a car 3 m. Calculate the work done.

We know that Work done (J) = Force (N) × Distance (m)

So, Work done = 5 N × 3 m = 15 J

Quizzes