Ohm’s Law

In 1828, Ohm studied the relation between current in a conductor and potential difference applied across it. He expressed this relation in the form of a law, known as Ohm’s law.

According to Ohm’s law, the electric current through a conductor is directly proportional to the potential difference across it, provided the physical conditions such as temperature and pressure remain unchanged.

V ∝ I

V = RI

V/I = R

where constant of proportionality R signifies the electrical resistance offered by a conductor to the flow of electric current. Resistance is the property of a conductor by virtue of which it opposes the flow of current through it.

The SI unit of resistance is ohm. It is expressed by symbol Ω (read as omega).

Most of the metals obey Ohm’s law and the relation between voltage and current is linear. Such resistors are called ohmic. Resistors which do not obey Ohm’s law are called non-ohmic. Devices such as vacuum diode, semiconductor diode, transistors show non ohmic character.