# Electric power

**Definition of electric power**

The power learned in the work and Energy is defined as the work done during a certain time interval. Work is a process of energy change so that power can be understood as a change in energy that occurs during a certain time interval.

Electric power is a change in electrical energy during a certain time interval. In a review of electrical potential, it is explained that changes in electric potential energy occur when an electric charge passes through an electric potential difference.

**Equation of electric power**

Mathematically the change in electric potential energy (ΔEP) is proportional to the charge (Q) and the electric voltage (V), expressed by the equation ΔEP = Q V. Power is a change in electrical potential energy over a certain time interval, mathematically expressed through equation 1:

The electric charge that flows during a certain time interval is an electric current, mathematically expressed through the equation I = Q/t. Equation 1 can be changed to equation 2:

Based on these two equations it can be concluded that changes in electrical energy during a certain time interval occur when an electric current passes through a certain electric potential difference. Electric power is proportional to the strength of the electric current and electric potential, so if the electric current and/or electric potential increase, the electric power also increases.

If an electric current flows through a resistor that has a constant electrical resistance, the electric power can be calculated using equation 3 or equation 4.

**Unit of electric power**

Based on equation 1, the International System unit of Energy is Joule and the International System unit of time is second so that unit of the electric power is Joule/second, abbreviated J/s. Joule/second is also called Watt. 1 Watt = 1 Joule/second.

Based on equation 2, the unit of electric potential is Volt and the unit of electric current is Ampere so that the unit of electric power is Volt Ampere, abbreviated VA.