Electrical Engineering ⇒ Topic : Important points of electromagnectic induction

The following points may be noted carefully

• The basic requirement for inducing e.m.f in a coil is not the magnetic flux linking the coil but the change influx linking the coil. No change influx, no e.m.f induced in the coil.
• The change in flux linking the coil can be brought about in two ways. First, the conductors (or coils) are moved through a stationary magnetic field as is the case with d.c. generators.Secondly, the conductors are stationary and the magnetic field is moving as is the case with a.c. generators. In either case, the basic principle is the same i.e. the amount of flux linking the conductors (or coils) is changed.
• The e.m.f and hence current in the conductors (or coils) will persist so long as the magnetic flux linking them is changing.

Note. We have seen that when magnetic flux linking a conductor changes, an e.m.f. is induced in it. An equivalent statement is like this : When a conductor cuts magnetic field lines , an e.m.f is induced in it. If the conductor moves parallel to the magnetic field lines, no e.m.f. is induced. This terminology is very helpful in visualising the concept of production of e.m.f