Q: A coil of 800 turns and 50 cm^2 area makes 10 rps about an axis in its own plane in a magnetic field of 100 gauss perpendicular to this axis. What is the instantaneous induced emf in the coil?

Sol: A = 50 cm^{2} = 50 × 10^{-4} m^{2}

N = 10 rps , N = 800

B = 100 gauss = 100 × 10^{-4} T = 10^{-2} T

Now, e = e_{0} sin ωt = NBAω sin ωt

e = 800 × 10^{-2} × 50 × 10^{-4} × 2π × 10 sin(20πt)

or , e = 2.5 sin (20πt) volts.