Current flowing through a conductor produces heat. This heat depends on quantity of current flowing through the conductor, time and resistance of the conductor. We can write:

H α I²

H α R

H α t

By combining these three relation we get:

H α I²Rt

H = K. I²Rt where K is a constant.

K= (H/(I²Rt))

K= H

for I=1 Amp., R= 1 ohm and t= 1 sec.

K becomes equal to heat generated at this condition. It is found heat generated is 0.24 calorie.

∴ H=0.24 I²Rt

This is also known as Jouls Law of Heating.

Also remember. 1 Calorie = 4.2 Joul

The above video contains explanation of heating effect of current through a conductor. The equation derivation is also shown.

Why 0.24 added while breaking proportionality is clearly explained.