Principle of Conservation of Energy:

The principle of conservation of energy states that the energy may neither be created nor destroyed. It may only be got converted from one form into another form. Thus, electrical energy may be transformed into heat energy as in case of electric-iron or in the case of Geysers utilized for heating water. Likewise, electrical energy may be transformed into light energy or mechanical energy and vice-versa. Though, the total energy content in a given system of bodies is constant.

According to principle of conservation of energy, following two points should be noted.

 (i) If some work is done (i.e. supplied) on the body, the energy content of body is enhanced by the amount of this work.

 (ii) If some work has been supplied (i.e. given away) by a body to other parts of the system, the energy content of the body is reduced by the amount of this work given away.

The above referred statements are also termed as Work-Energy equation.