Work and energy transfer

When energy is transferred mechanically or electrically, work is done. For example, a force can transfer energy by moving an object, or an electric current can transfer energy to a component.

The work done is equal to the energy transferred. Both are measured in joules ($$\mathrm{J}$$).

Work done by a constant force

For a constant force, the work done is the force multiplied by the distance moved in the direction of the force:

Here, $$W$$ is work done in joules, $$F$$ is force in newtons ($$\mathrm{N}$$), $$d$$ is distance moved in the direction of the force in metres ($$\mathrm{m}$$), and $$\Delta E$$ is energy transferred in joules.

For example, if a constant force of $$10\ \mathrm{N}$$ moves an object $$3\ \mathrm{m}$$ in the direction of the force, the work done is $$10 \times 3 = 30\ \mathrm{J}$$. The energy transferred is also $$30\ \mathrm{J}$$.

Only movement in the direction of the force counts in this calculation. If there is no movement in that direction, the force does no work. One joule is equal to one newton metre: $$1\ \mathrm{J} = 1\ \mathrm{N,m}$$.