: a law in electricity: the strength or intensity of an unvarying electric current is directly proportional to the electromotive force and inversely proportional to the resistance of the circuit
Relationship between the potential difference (voltage), electric current, and resistance in an electric circuit. In 1827 Georg Simon Ohm discovered that at constant temperature, the current I in a circuit is directly proportional to the potential difference V, and inversely proportional to the resistance R, or I = V/R. Resistance is generally measured in ohms (). Ohm's law may also be expressed in terms of the electromotive forceE of an electric energy source, such as a battery, or E = IR. In an alternating-current circuit, when the combination of resistance and reactance, called impedance Z, is constant, Ohm's law is applicable and V/I = Z.