Joule’s Law of Heating | Joule’s Law of heating class 10

Last updated on April 13th, 2023 at 02:31 pm

In this post, we will discuss the heating effect of current, and Joule’s Law of heating. Class 10 students should find this useful as this post covers Joule’s Law of Heating class 10 syllabus. Joule’s law statement, formula, and brief explanation are also given here.

Joule’s Law of Heating | Joule’s Law of Heating for class 10

We will first state Joule’s law, and then discuss the formula that is used to calculate the heat produced by electric current.

State Joule’s law of heating | Joule’s Law of Heating statement

Joule’s law of heating states that the heat produced due to electric current is (i) directly proportional to the square of the current for a given Resistance (ii) directly proportional to resistance for a given current and (iii) directly proportional to the time of passage of current.
Joule’s law of electrical heating can be expressed by the equation H = I²Rt, where H is the heat caused by an electric current, I through a conductor of resistance, R for a time, t. 

Joule’s Law of Heating formula | Joule’s law of Heating class 10 formula

Joule’s law of electrical heating can be expressed by the equation H = I²Rt, where H is the heat caused by an electric current, I through a conductor of resistance, R for a time, t. 

Also, read this post to solve numerical: Heating effect of electric current class 10 Numericals

Explain Joule’s law of heating | What is Joule’s law of heating

In a conductor, due to thermal agitation, the free electrons are always in random motion making collisions with ions or atoms of the conductor.

When a voltage V is applied between the ends of the conductor, resulting in the flow of current I, the free electrons are accelerated. Hence the electrons gain energy at the rate of VI per second. The lattice ions or atoms receive this energy from the colliding electrons in random bursts. This increase in energy is nothing but the thermal energy of the lattice.

Thus for a steady current I, the amount of heat H produced in time t is
H = VIt …..… (1)
For a resistance R, V= IR
Hence,
H = I²Rt …….. (2) and
H =(V²/R) t ………(3)

The above relations were experimentally verified by Joule and are known as Joule’s law of heating.

With the help of equation (2) above we can state Joule’s law. From this equation, we find the following:

H α I²

H α R

H α t

Also by equation (3) above, H =(V²/R) t, the heat produced is inversely proportional to resistance for a given Voltage (PD) applied between the ends of the conductor.

Verification of Joule’s law

Joule’s law is verified using Joule’s calorimeter. It consists of a resistance coil enclosed inside a copper calorimeter.