Power is the rate at which energy is transferred. It is measured as the rate of energy per unit of time or joules per second.
An electrical circuit is a tool that transforms energy from one form to another. An electrical circuit receives energy from a variety of sources such as a battery, electrochemical cell or a generator, among others. When the energy is delivered to the circuit, it is transmitted to the load at a specific point on the circuit.
The rate at which the electrical energy is supplied to the circuit is called power. Power can also be the rate at which the energy is consumed by the load.