A mathematical equation that shows the relationship between electric voltage, current and resistance. Ohm’s Law was named after Bavarian mathematician and physicist Georg Ohm.

Ohm’s Law can be stated as three mathematical equations, all derived from the same principle. In the following equations, V is voltage measured in volts, I is current measured in amperes and R is resistance measured in ohms:

V = I x R

R = V / I

I = V / R

Knowing any two of the values of a circuit, one can determine the third using Ohm’s Law. For example, if a circuit has a current of 2 amperes, and a resistance of 1 ohm, then according to Ohms Law, voltage equals 2 (V = 2 x 1).

Typically, Ohm’s Law is only applied to DC circuits and not AC circuits.

Note well: The letter “E” is sometimes used in representations of Ohm’s Law for voltage instead of “V.”