Joule's Laws

Joule's laws are a pair of laws concerning the heat produced by a current and the energy dependence of an ideal gas to that of pressure, volume, and temperature, respectively. They are named after James Prescott Joule.

Joule's first law, also known as the Joule effect, is a physical law expressing the relationship between the heat generated by the current flowing through a conductor. Joule studied this phenomenon in the 1840s. It is expressed as:

where is the heat generated by a constant current flowing through a conductor of electrical resistance, for a time . When current, resistance and time are expressed in amperes, ohms, and seconds respectively, the unit of is the joule. Joule's first law is sometimes called the Joule–Lenz law since it was later independently discovered by Heinrich Lenz. The heating effect of conductors carrying currents is known as Joule heating.

Joule's second law states that the internal energy of an ideal gas is independent of its volume and pressure, depending only on its temperature.