Joule effect

Joule effect and Joule's law are any of several different physical effects discovered or characterized by English physicist James Prescott Joule. These physical effects are not the same, but all are frequently or occasionally referred to in the literature as the "Joule effect" or "Joule law" These physical effects include:
"Joule's first law" (Joule heating), a physical law expressing the relationship between the heat generated and the current flowing through a conductor. 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. Magnetostriction, a property of ferromagnetic materials that causes them to change their shape when subjected to a magnetic field. The Joule effect (during Joule expansion), the temperature change of a gas (usually cooling) when it is allowed to expand freely. The Joule–Thomson effect, the temperature change of a gas when it is forced through a valve or porous plug while keeping it insulated so that no heat is exchanged with the environment. The Gough–Joule effect or the Gow–Joule effect, which is the tendency of elastomers to contract if heated while they are under tension.

Between 1840 and 1843, Joule carefully studied the heat produced by an electric current. From this study, he developed Joule's laws of heating, the first of which is commonly referred to as the Joule effect. Joule's first law expresses the relationship between heat generated in a conductor and current flow, resistance, and time.

The magnetostriction effect describes a property of ferromagnetic materials which causes them to change their shape when subjected to a magnetic field. Joule first reported observing the change in the length of ferromagnetic rods in 1842.

In 1845, Joule studied the free expansion of a gas into a larger volume. This became known as Joule expansion. The cooling of a gas by allowing it to expand freely is occasionally referred to as the Joule effect.