Explain jouls heating law ?

Joule's law states the amount of heat production in a conductor is : Directly proportional to the square of electric current flowing through it. Is directly proportional to the resistance of the conductor. Directly proportional to the time for which electric current flows through the conductor. 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. Electric arc and electric welding also work on the principle of heating effect of current. In some cases such as transformers and dynamos, Joule heating effect is undesirable. These devices are designed in such a way as to reduce the loss of energy due to heating.