Therefore,
there is no change in the magnetic flux through coil C1 and the current in
coil C1 drops to zero When the key is released, the current in C2 and the
resulting magnetic field decreases from the maximum value to zero in a
short time This results in a decrease in magnetic flux through coil C1
and hence again induces an electric current in coil C1* The common
point in all these observations is that the time rate of change of magnetic
flux through a circuit induces emf in it