The change in flux linkages can be caused in which of the following ways ?

The correct answer is D. All of the above.

The change in flux linkages can be caused in any of the following ways:

• The flux is constant with respect to time and is stationary and the coil moves through it. This is the case when a coil is placed in a uniform magnetic field and then moved through the field. The flux linkages will change because the area of the coil that is in the field is changing.
• The coil is stationary with respect to flux and the flux varies in magnitude with respect to time. This is the case when a coil is placed in a time-varying magnetic field. The flux linkages will change because the magnitude of the flux is changing.
• Both the changes mentioned above occur together, i.e., the coil moves through a time varying field. This is the case when a coil is placed in a non-uniform magnetic field and then moved through the field. The flux linkages will change because both the area of the coil that is in the field and the magnitude of the flux are changing.

In all of these cases, the change in flux linkages will induce an emf in the coil. The magnitude of the emf will be proportional to the rate of change of the flux linkages.