The relationship between electric power, electric current and electric resistance is given by the formula P = I^2 * R, where P is the electric power in watts, I is the electric current in amperes, and R is the electric resistance in ohms. This formula is known as Joule's law and expresses the fact that the electric power dissipated in a resistive element is proportional to the square of the electric current flowing through it and to its resistance. Therefore, if the electric power and the electric resistance of a circuit are known, the electric current can be derived by rearranging the formula as follows: I = sqrt(P/R).

An alternative formula for determining the electric current can be derived from:

\(P\) \(=\) \(I^2\) \(\cdot\) \(R\)

\(I\): the electric current

\(R\): the resistance

\(P\): the electric power

The SI unit of electric is: \(ampere\text{ }(A)\)

## Find I

Use this calculator to determine the electric current when the electric power and the resistance are given.

the resistance

\(R\)

\(ohm\)

the electric power

\(P\)

\(watt\)