Question

What do you understand by the thermal effect of electric current?

Answer 1

Hint: Flow of electric current through a conductor causes free electrons to collide with their atoms due to which major fraction of kinetic energy gets converted into heat energy and temperature of the conductor rises.

Formula used:
$W={{I}^{2}}Rt$

Complete step by step answer:
Conductors are the type of materials that allow the flow of charge, or electric current, in one or more directions. They are commonly made up of metals such as silver, copper or aluminum, and referred to as electric conductors.

The heat energy released on passing electric current in a conductor is called ‘Joule heat’ and this effect is known as ‘Joule’s effect of heating’.

Let’s consider $Q$ amount of coulomb charge passes through the conductor in a time interval of $t$ seconds, resulting in $I$ amount of current flowing through the conductor. The amount of heat energy produced will be given by,

$W=VQ$

where $W$ is the work done and$V$is the potential difference across two points in circuit

We know, $Q=It$
$W=VIt$

Also, $V=IR$ according to Ohm’s law

It gives, $W={{I}^{2}}Rt$

Joule’s law of thermal heating states that: The heat produced per unit time, on passing electric current through a conductor at a given temperature, is directly proportional to the square of electric current.

Heat energy produced $H={{I}^{2}}Rt$

Heat generated in a circuit depends upon three factors:
(i) The resistance $R$ of the conductor. High value of resistance will produce more heat in the circuit.
(ii) The time $t$ for which current flows in the circuit. The longer the current flows, the larger the amount of heat will be produced.
(iii) The value of current $I$ in the circuit. The higher the current, larger the amount of heat will be produced.

Additional information:
We can calculate the value of heat produced in calories by:

$W=JH$

Where, $W$ is the mechanical energy in Joule
$H$ is the heat energy in calories
$J$ is the Joule’s constant

Value of Joule’s constant $J=4.2\dfrac{\text{Joule}}{\text{Calorie}}$
$J$ is also known as the mechanical equivalent of heat.

$H\text{ (cal) = }\dfrac{{{I}^{2}}Rt\text{ (joule)}}{J}$

Note: While finding the amount of heat produced, students should prefer working in SI units only, to avoid any kind of calculation error. Later, units of heat can be changed from Joule to Calories.