Abstract: The apparatus comprises a pair of opposed coil assemblies between which a workpiece to be heated is moved, each coil assembly including a plurality of loop windings arranged generally in a plane parallel to the plane of movement of the workpiece between the coil assemblies, the windings being arranged in pairs with the windings in each pair being aligned transversely in the direction of movement of the workpiece, adjacent end portions of the windings of each pair being turned to extend substantially perpendicularly to the plane of the remainder of the windings and away from the plane of movement of the workpiece. The arrangement allows the width of the coil assemblies to be altered in dependence upon the width of a workpiece to be heated.