We are familiar with the different forms of energy that can be transferred from one form to another. Heat is produced by rubbing the palms of hands together. By rubbing two sticks of wood together, a five may be started. When an object is released from a certain height, heat is developed as the weight strikes the ground. These are some examples which show that mechanical energy can be converted into heat energy.

In the reverse way, heat can also be converted into mechanical energy. The steam engine, diesel engine and jet propulsion engine converts heat into mechanical energy. In all these engines, fuel is burned to produce heat and this heat in turn is used to expand the volume of gas and hence mechanical work is done.

This relationship between heat and mechanical energy is dealt in thermodynamics. But we know that energy can be converted from one form into another. Hence, Thermodynamic deals with heat and interrelationship with other forms of energy like mechanical, chemical, electrical, magnetic etc.