James Prescott Joule FRS was an English
physicist and
brewer, born in
Salford, Lancashire. Joule studied the nature of
heat, and discovered its relationship to
mechanical work. This led to the theory of
conservation of energy, which led to the development of the
first law of thermodynamics. The
SI derived unit of energy, the
joule, is named after him. He worked with
Lord Kelvin to develop the absolute scale of
temperature, made observations on
magnetostriction, and found the relationship between the
current through
resistance and the heat dissipated, now called
Joule's law.