Arrangement to give constant magnetic couple - involves rotating magnetic assembly which does not cut any magnetic lines

摘要

To generate a constant couple a magnet is placed at a fixed distance from a wire. A current passing through this wire causes a force on the wire and an equal and opposite force on the magnet end. When the magnet and wire are attached to the same rotatable body at different distances from the axis of rotation then a turning couple results. The perfected embodiment has a bar magnet mounted inside a rectangular coil through which current is passed. Preferably an annular ring of soft iron is placed coaxially with the axis of rotation and in the same plane as the magnet. Rotation is said to take place with no flux cutting and hence with no back e.m.f.