Electromagnetic induction heater with magnetic flux diffusing members

An electromagnetic induction heater comprising an iron core of a transverse dimension W.sub.1 and having a longitudinal axis, ends and a central part, said iron core being wrapped with an electric wire to form a coil around said core, said ends of said iron core each being fixed to elongated magnetic flux diffusing members having longitudinal axes disposed substantially perpendicularly to the longitudinal axis of said iron core, said magnetic flux diffusing members being connected to a metal plate and each having length W.sub.2 which is greater than said transverse dimension W.sub.1 of said iron core,

• wherein a magnetic flux flows through a closed magnetic circuit comprising said iron core, said magnetic flux diffusing members and said metal plates by connecting said electric wire to a low frequency alternating current power source, the magnetic flux being diffused by spreading from dimension W.sub.1 to length W.sub.2, so that said metal plate is heated by Joule heat, and
• wherein a ratio of said length W.sub.2 to said transverse dimension W.sub.1 is between 2 and 70.