Ohms Law gives the relation between voltage and current. Whenever an electric potential difference (V) is applied across two points of the conductor, the current (I) flows through it. The flow of current is opposed by the resistance (R) of the conductor. The value of resistance (R) will remain constant for all value of voltages and currents. This relation was expressed first of all by a German Scientist, George Simon Ohm that is why it is called Ohm’s Law.

Ohms law
Graph Represents Ohm’s Law

Ohm’s Law states that current flowing between two points of the conductor is directly proportional to applied voltage or potential difference between two points of conductor. Provided the temperature and other physical conditions of the conductor do not change.


V α I

In other words, Ohm’s Law can also be defined as,

The ratio of potential difference across any two points of a conductor to the current flowing through the conductor is always constant. This constant is called resistance (R).

The linear relationship (I α V) does not apply to all non-metallic conductors. For example for silicon carbide, the relationship is given by V = kIX where k and x being constants; x is always less than unity.

All resistors do not obey Ohm’s law. A resistor that obeys Ohms’s law is known as linear resistor and a resistor that does not obey Ohm’s Law is called non-linear resistor.

Drawbacks or Limitations of Ohm’s Law

  • Ohms Law is not applied to non-linear resistors.
  • Ohms law is not applicable to unilateral components, such as semiconductor components, because semiconductor devices have no current and voltage characteristics same in both direction like bilateral component , Means current do not vary proportional to the applied voltage in semiconductor.
  • It is not applied to arc lamps.
  • Electrolytes where enormous gases are produced on either electrode.
  • It is not applied to unilateral elements.

Advantage of Ohm’s Law

  • It makes the calculation easy and simple.

Applications of Ohm’s Law

  • Ohms Law applies to linear circuits to find resistance, current and voltages. It makes the calculation easy and simple.