Question

What is Joule’s heating effect? How can it be demonstrated experimentally? List its four applications in daily life.

Answer 1

Hint: We know that when current passes through a conductor for a particular time there is a heating effect. This heating effect is known as the joules heating effect. According to joules heating effect the heat produced will be the product of current voltage and the time for which current flows through the conductor

Complete step by step solution:
Joules heating effect is the effect in which a conductor gets heated when current is passed through it for a particular time. Suppose a current, I flow through a conductor for a time t, the potential difference across it is V. Then according to joules heating effect, the heat produced is given as
$H = IVt$................(1)
 Where I is the current, V is the potential difference and t is the time taken.
From Ohm's law we know that voltage is a product of current and resistance.
$ \Rightarrow V = IR$
 Hence, we can write the equation 1 as
$ \Rightarrow H = I \times IR \times t$
$ \Rightarrow H = {I^2}Rt$
This is the equation for heat produced according to the joules heating effect.
In order to prove it experimentally let us immerse a conductor through which current flows into a vessel containing water. let the initial temperature of the water be ${\theta _1}$ and the final temperature of the water be ${\theta _2}$ .
The heat absorbed by the water is given as the product of mass of the water and the change in temperature.
$ \Rightarrow H = m\Delta \theta $
$ \Rightarrow H = m\left( {{\theta _2} - {\theta _1}} \right)$
This value will be equal to the value given by Joule’s heating effect.
$ \Rightarrow m\left( {{\theta _2} - {\theta _1}} \right) = {I^2}Rt$
Hence, we can prove the joule heating effect.
The common applications of Joule heating effect in our daily life are
1.Electrical bulb works using joules heating effect.
2.Electrical fuse used for protecting household appliances also uses the joules heating effect
3.Joules heating effect is also used in the iron box.
4. Appliances such as electric oven, room heaters, geysers also use joules heating effect.

Note: The joule's heating effect is an irreversible process. That is, if we supply current in one direction through a resistor then the resistor gets heated. But we cannot cool the resistor by reversing the direction of current. So, this process is not reversible.