Joule’s Law of Heating:
A conductor contains a large number of free electrons. When a potential difference is applied across its ends, these free electrons gain kinetic energy and draft towards the higher potential end. During their motion, they collide with the ion cores as well as with other electrons resulting in the development of heat energy. The heat energy so produced can be obtained from Joule’s Laws.
Statement of Joule’s Law:
1. For a given conductor i.e, for a given resistance (R) and for a given time interval (t), the amount of heat (H) developed in the conductor is directly proportional to the square of the current (i) flowing through it.
H ∝ i2 when R & i are constants.
2. For a given current through a conductor for a given time interval, the heat developed is directly proportional to the time of flow of the current.
H ∝ R2 when i & t are constants.
3. When a given current is sent through a given conductor, the heat developed is directly proportional to the time of flow of the current.
H ∝ t2 when i & R are constants.