  In this paper we discuss the phenomenon of resonance that we predict will
occur when a superconducting coil is submitted simultaneously to a magnetic
field and to an external force. When both the force and the magnetic field are
constant in time the coil should oscillate mechanically around an equilibrium
position like an ideal harmonic oscillator, and should have induced in it an
alternating current of same frequency. We obtain an expression for the
resonance frequency, which is directly proportional to the applied magnetic
field and depends also on the wire superconducting properties. We discuss also
a setup with no built-in magnet, in which the coil is driven by a mechanical
oscillator, and thus the force varies cyclically with time. A measurable
alternating current may be induced in the device for an amount of magnetic flux
as small as one flux quantum, so that the device is an excellent magnetometer.
