To prevent contact failure in a ground conductor electrically connecting a coil for a generator using an iron core coil with an iron core, resulting from oscillation.

The iron core coil is constituted by inserting an either projecting part 1a of the U-shape iron core 1 in a through hole 4a of a bobbin 4 around which an exciter coil 2 is wound so that earth of the coil may be connected to the iron core through the ground conductor 11. The ground conductor is brought into contact with the iron core, sandwiched between the iron core and the bobbin. The projection 12 which protrudes on the iron core side is provided at the ground conductor to bring the projection into contact with the iron core. The projection is brought into contact with the iron core by elastic return force of the bobbin, thus obtaining complete electrical connection of the ground conductor with the iron core.