Abstract: The invention relates to an inductor having two parallel main heating conductors which are interconnected at one of their ends via a bridge-shaped branch and are connected at their other end to a transformer, the connections also forming a bridge-shaped conductor branch. The characterizing feature of the invention is that disposed at least at one end of the parallel main heating conductors is a separate auxiliary inductor which is mounted displaceably in relation thereto and has two conductor portions parallel with the main heating conductors and inductively coupled thereto which are collectively interconnected at one of their axial ends via a bridge-shaped conductor branch determining the end of the heating zone and at the other end via a tunnel-shaped return conductor which over the whole displacement length is disposed beneath the bridge-shaped branch of the main heating conductors and is inductively coupled thereto.