Let us take up the case of a rectangular coil of N turns rotating
in the anticlockwise direction, with an angular velocity of radians per
second in a uniform magnetic field as shown in Fig 3.1. Let the time be
measured from the instant of coincidence of the plane of the coil with the
X-axis. At this instant maximum flux, max, links with the coil. As the coil
rotates, the flux linking with it changes and hence e.m.f. is induced in
it. Let the coil turn through an angle in time ‘t’ seconds, and let it
assume the position as shown in Fig 3.1. Obviously = t.