As a result, the effective area
of the coil exposed to the magnetic field lines changes with time, and from
Eq (6 1), the flux at any time t is
FB = BA cos q = BA cos wt
From Faraday’s law, the induced emf for the rotating coil of N turns
is then,
d
d
–
–
(cos
)
dt
d
B
N
NBA
t
t
Φ
ε
ω
=
=
εThus, the instantaneous value of the emf is
ω
ω
= NBA
sin
t
(6 19)
where NBAw is the maximum value of the emf, which occurs when
sin wt = ±1