Ohm's law is a mathematical formula that expresses the relationship between the electromotive force, electric current, and resistance in a circuit. This relationship was discovered by the German physicist Georg Ohm, and was published in 1827. When applied to a direct-current circuit, Ohm's law states that the electromotive force (E), measured in volts, equals the current (I) in amperes multiplied by the resistance (R) in ohms:E = IR