Power is the rate at which energy is transferred, as shown in the equation below.
Note: 1 watt = 1 Joule per second
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:
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 involves moving electrons, which produces a current. It represents the energy needed to overcome the resistance in a circuit’s wiring.
Below is the equation relating work done to the force applied and the distance travelled in the direction of that force.
A child applies 5 N to move a car 3 m. Calculate the work done.