Restoring force between two noncoaxial circular coils

Considered here are the forces between two current-carrying circular coils, one of which, the primary coil, has a larger diameter than the other, the secondary. In the case in which the secondary coil´s central axis does not coincide with that of the primary, there exists a transverse force which we call the restoring force. It is found that this force decreases with increasing distance between the coils and changes sign. This paper presents a calculation of this force and its characteristics. Finally, it introduces some experimental results.