The main difference at this stage, between the time-dependent and time-independent fields, is in the process of induction:
A time-dependent field produces an electric field and that, in turn, induces currents in conducting materials. This induction is
fundamental to the operation of many very important devices, including transformers and generators. There are two
mechanisms of induction: one is due to change in the magnetic flux; the other due to motion in the magnetic field. Both
are discussed since they can exist simultaneously in the same device and because both are important in design.