Ohm's law

Law that states that, for many materials over a wide range of conditions, the current flowing in a conductor maintained at constant temperature is directly proportional to the potential difference (voltage) between its ends. The law was discovered by German physicist Georg Ohm in 1827. He found that if the voltage across a conducting material is changed, the current flow through the material is changed proportionally (for example, if the voltage is doubled then the current also doubles).

If a current of I amperes flows between two points in a conductor across which the potential difference is V volts, then V/I is a constant called the resistance R ohms between those two points. Hence: V/I = R or V = IR. Not all conductors obey Ohm's law; those that do are called ohmic conductors.