Joule heating effect

The Joule heating effect is the physical phenomenon whereby the passage of electric current in a metallic conductor produces heat.

The effect is the physical phenomenon on which the heating of the cathode filament of a x-ray tube depends. The electric current flowing through the tungsten filament of a x-ray tube usually varies between 3 and 8 A, generated by applying a voltage of between 10 and 20 V to the filament itself, i.e. it is a low voltage current (cf. high voltage tube current).

History and etymology

The name of the effect is in honor of the scientist, James Prescott Joule (1818-1889), who discovered it. The unit of energy, the joule (symbol J) is also named after him.