Question

State Joule's Law of heating and derive an expression for heat energy.

Answer 1

Dear Student ,

Joule’s law of heating states that when a current ‘i ' passes through a conductor of resistance ‘r’ for time ‘t’ then the heat developed in the conductor is equal to the product of the square of the current, the resistance and time.

H = i ² rt

The reason behind the heat produced is the collision of the free electrons with the lattice ions or atoms while accelerating in presence of the external electric field.

Now,
we know that

volt= work done/ total charge or v = w/q

from this, we get,
w= vq

and, we know that
current i = q / t

so,
q = it

And, We know, from ohms law
v = ir

putting this in the previous equation (i.e. w =vq)
we get w = (ir)(it)

w = irit = i²rt joule

as work is stored as heat
so,
H = I²RT Joules

Regards