Joule's Work: 3 Main Findings
Joule's Law is a physical law expressing the relationship between the heat generated by the current flowing through a conductor. In his experiment, he found the amount of heat per second that develops in a wire carrying a current is proportional to the electrical resistance of the wire and the square of the current.
It is closely related to Ohm's Law
(discovered in 1860's).
The Joule is a unit of work that is equal to the work done by a
force of one newton acting through one meter. It was named in
honor of Joule, who first estimated the mechanical equivalent
of heat as 838 ft·lbf of work to raise the temperature of a pound
of water by one degree Fahrenheit in 1843. By refining
experiments, his final value was 772.692 ft·lbf/Btu in 1850, his
closest value to today's accepted value, 4.184 J/Cal.
The Joule-Thompson Effect is the temperature change that
happens when a gas expands without producing work or
transferring heat. For any given pressure, a real gas has a
Joule-Thomson inversion temperature (mJT), above which
expansion at constant enthalpy causes the temperature to rise, and below
which expansion at constant enthalpy causes cooling. At ordinary
temperatures and pressures, all real gases (except hydrogen and helium)
cool when they expand.
