Born in Salford, England. A physicist, he shared in discovering the law of the conservation of energy. Two German physicists, Hermann von Helmholtz and Julius von Mayer, and Irish/Scottish physicist Lord Kelvin, also worked on the law of physics. The law states that energy used up in one form reappears in another and is never lost.

In 1840, he stated a law, now called Joule's Law, that heat is produced in an electrical conductor. The International unit of energy, the joule, is named in his honor.