**Ohm’s Law**

**Definition **: According to the Ohm’s law at constant temperature, the current flowing through a conductor is directly proportional to the potential difference across the conductor.

Thus, if I is the current flowing through a conductor and V is the potential difference (or voltage) across the conductor, then according to Ohm’s law.

I ∞ V (when T is constant)

where R is a constant called the **resistance of the conductor. **

Equation (i) may be written as,

V = I × R ……(ii)

**Unit of resistance**

The SI unit of resistance (R) is ohm. Ohm is denoted by the Greek letter omega (Ω).

From Ohm’s law,

Now, if, V = 1 volt and I = 1 ampere

Thus, 1 ohm is defined as the resistance of a conductor which allows a current of 1 ampere to flow through it when a potential difference of 1 volt is maintained across it.

**Results of Ohm’s law **

- Current flowing through a conductor is directly proportional to the potential difference across the conductor.

- When the potential difference in a circuit is kept constant, the current in inversely proportional to the resistance of the conductor.
**I****∝****1/R** - The ratio of potential difference to the current is constant. The value of the constant is equal to the resistance of the conductor (or resistor).
*V*/*I*=*R*