Question

State Joule's law of heating.

Hint:

This law explains why wires get hot when used and why fuses blow when current exceeds a safe limit.

Answer 1

Joule’s Law of Heating:

Joule’s law of heating states that: The heat produced in a conductor due to the flow of electric current is directly proportional to: – The square of the current flowing through it.
– The resistance of the conductor.
– The time for which the current flows.

Mathematical Expression: \[ H \propto I^2 \] \[ H \propto R \] \[ H \propto t \] Combining all three relations: \[ H = I^2 R t \] where
H = heat produced
I = current
R = resistance
t = time

Explanation:
– If current increases, heat produced increases rapidly because it depends on the square of current.
– Higher resistance produces more heat.
– More time of current flow results in more heat generation.

Conclusion:
According to Joule’s law, the heat produced in a conductor is given by: \[ \boxed{H = I^2 R t} \] This principle is used in electric heaters, irons and toasters.