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As shown in the figure, a circular coil with a radius of R = 10cm has a total of 100 turns and rotates uniformly at a speed of n = 600r / min around the central axis OO 'perpendicular to the direction of the magnetic field in a uniform magnetic field with magnetic induction B = 5 / π 2 & nbsp; t, The timing starts when the coil turns to the neutral plane. (1) write out the instantaneous value expression of the alternating electromotive force generated in the coil. (2) calculate the instantaneous value of the electromotive force when the coil passes 1 / 60s from the position shown in the figure. (3) calculate the average value of the electromotive force when the coil passes 1 / 60s from the position shown in the figure;
1. Clockwise e = nbswsinwt, where BS = (5 / π ^ 2) π * 0.01 = 0.05 / π, n = 100, n = 10R / s, w = 2 π, n = 20 π
So e = (5 / π) * 20 π sin (20 π T) = 100 sin (20 π T)
2. When t = 1 / 60 s, e = 100 * sin (π / 3) = 50 * sqrt (3) v
3. The initial flux is NBS = 5 / π, 1 / 60s turns π / 3, and the flux is nbscos (π / 3) = 2.5 / π
The average value of EMF is Δ Φ / Δ t = (2.5 / π) / (1 / 60) = 150 / π
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