Ohm’s Law

Ohm’s Law

The electricity is the flow of charges from positive to negative or vice – versa. It is also said the flow of electrons. The one of important law of electricity is Ohm’s law. This is also called a fundamental law of electricity. It gives the relationship between basic electrical quantities. These basic quantities are current, resistance and voltage.

We know that resistance is the opposite force which restricts the flow of electricity. The voltage is the electromotive force which is the reason for the movement of electrons and this is the cause of flow of electric current which is measured in ampere. What is the relation between these three main quantities? How they are connected with each other? How the reduction in one quantity can affect the other? All these questions are answered by Ohm. Let’s discuss about this law and its applications.

What is Ohm’s Law?

It states that “the current through the conductor is directly proportional to the potential difference across its ends provided the temperature remains constant.

Consider a conductor across which voltage is applied,

Ohm’s Law

Current starts flowing through a conductor, we can also express current in terms of Voltage and Resistance as V = IR.


V = Voltage applied to the conductor,

R = Resistance of the conductor,

I = Current flowing through the metal conductor.

The Electric Current flows from high potential to the low potential point. This is due to the fact that the resistance offered by the point at low potential point is less and hence current gets easy path to flow.

Ohm’s Law Formula: We know that when Voltage is applied across any conductor its Voltage increases.

I α V

But every Conductor offers some resistance so Current can be expressed as \(I\,=\,\frac{V}{R}\).


R = the constant of proportionality and is known as the resistance of the given conductor,

V = potential difference across the ends,

I = current in the Conductor.

The ohm’s law is the relation between three variables Voltage (V), Current (I) and Resistance (R):

We can rewrite above equation in two different equations as V = IR.

We will call this ohm’s law current equation.

In terms of Resistance it is expressed as \(R\,=\,\frac{V}{I}\),

We will call this ohm’s law resistance equation.

How to find Ohm’s Law?

Problem: A 10 V battery is connected to the electric bulb of resistance of 20 ohms. Find the current flowing through the electric bulb?

Solution: Given,

Voltage (V) = 10 Volts

Resistance (R) = 20Ω

The current flowing through the electric bulb is given by \(I\,=\,\frac{V}{R}\),

\(I\,=\,\frac{10}{20}\) = 0.5 Amperes.

So, the current flowing through the bulb is 0.5 amperes.