In a rotating frame, to first order in ω, the main effect is a coriolis force This unbalanced force will cause electrons to react by setting up a magnetic field vector B that the magnetic force balances the coriolis force.
where is the number of turns of the ring. If ω changes (and there is time for the electron to rearrange) then B also changes and so does Φ. An emf will be induced and a current will flow. This is
The total charge flowing through the ballastic galvanometer, as the ring is stopped, is