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What is Ohm’s Law?

Physics | 7-14 yrs | Interactive

Definition of Ohm’s law

Ohm’s Law is the mathematical relationship between electric current, resistance and voltage.

Ohm’s law states that the current through a conductor, between two points is directly proportional to the voltage across the two points.

The principle is named after the German scientist Georg Simon Ohm.

Ohm’s Law formula

The formula for Ohm’s Law is as follows:

V = IR


V is Voltage
I is Current
R is Resistance

How does Ohm’s Law work?

A continuous flow of free electrons, through the conductors of a circuit is called current. An electric circuit is formed when a conductive path is created to allow the free electrons to continously move.

The force that is motivating the flow of electrons is called voltage. It is a specific measure of potential energy that is always relative between two points.

Free electrons tend to move through conductors with some degree of friction, or opposition to motion. This opposition to movements of free electrons is called resistance.

Using this Law, we are able to analyse electric circuits. If you know any two values, you can analyse the third one. Sometimes electric circuits are complicated, but this equation is so important, it solves those complicated circuit values as well. It is applied in almost all circuit studies.

Practical application of Ohm’s Law

  1. Ohm’s Law is used in electrical heaters to generate heat. The conductor is designed to create resistance to the flow of free electrons and so the resistance creates heat.
  2. Ceiling and other fans, use Ohm’s Law as well. The speed is regulated using Ohm’s Law application.
  3. Light Bulbs emit light using Ohm’s Law

Here is a simple, fun exercise. Walk around your house and see which object uses Ohm’s Law! Make a list and compare it with your friends. Have fun!