Introduction to HeatWe know that a nail becomes hot when it is hit with a hammer. Rubbing of hands together generates heat.
A seventeenth-century scientist, Robert Hooke, explained heat as brisk and violent agitation of parts of a body. In the nineteenth century, James Prescott Joule, by his famous experiments showed that mechanical energy and heat energy are equivalent. During rubbing of hands, the mechanical energy spent in overcoming friction is converted to heat. Thus, heat is a form of energy. Energy is the ability to do work. Therefore, heat has the ability to do work.For example, steam engine pulls a train by converting heat into mechanical energy.