A solenoid has a coil C of wire wound tightly about its centre, as shown in the figure below.
The coil C has 96 turns. The uniform magnetic flux 
(in Weber) in the solenoid is given by the expression
where 
is the current (in amperes) in the solenoid.
Calculate the average electromotive force (e.m.f.) induced in coil C when a current of 
is reversed in the solenoid in a time of 
.
The d.c. supply in the figure above is now replaced with a sinusoidal alternating supply. Describe qualitatively the e.m.f. that is now induced in coil C.
.
