Joule's experiment converts

Joule's experiment converts work into heat

Accurate investigation of the relationship between heat developed and mechanical work spent was taken up by the British Scientist James Prescott Joule. The main aim of his investigations was to determine exactly the ratio between the work done and the quantity of heat produced.

Joule used different arrangements for doing the work, W in different ways and measured the corresponding amount of heat, H produced in each case.  In all the cases he found that the expenditure of the same amount of work always produced the same amount of heat.  Every time he found that 4186 joule of work was spent to produce the same amount of heat which could raise the temperature of one kg of water through 10C.  He established the relation, W/H to be a constant quantity. The constant relation W/H was represented symbolically by the letter ‘J’.  J is known as Joule's mechanical equivalent of heat.  ‘Symbolically, we can write :

                           W/H = J  or W = JH