emf = N d flux /dt
emf = 660 B pi r^2 d/dt (sin 2 pi t/T)
when t = .024, t/T = 1/8
T = .192 second
so
emf = -660 (pi r^2) (2 pi/T)B cos (2 pi t/T)
now I do not know what "average means. Obviously the average of a cosine function is zero.
You might guess they mean magnitude in which case
.095 = 660(pi r^2)(2 pi/T) B
or they might mean root mean square or something in which case multiply that B by 1.414
A circular coil (660 turns, radius = 0.037 m) is rotating in a uniform magnetic field. At t = 0 s, the normal to the coil is perpendicular to the magnetic field. At t = 0.024 s, the normal makes an angle of 45o with the field because the coil has made one-eighth of a revolution. An average emf of magnitude 0.095 V is induced in the coil. Find the magnitude of the magnetic field at the location of the coil.
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