Naming this “the Mechanical Equivalent of Heat,” he set out to discover its value. To do so, Joule connected his dynamo to a falling weight via a system of ropes and pulleys. As the weight fell, it turned the dynamo, generating first electricity and then heat, which as before warmed a tube of water. Joule could now equate the height by which a known weight fell to the amount of heat that was created. In other words, he could measure the Mechanical Equivalent of Heat.
