As shown in the figure, line a is the image of the sinusoidal alternating current generated when the coil rotates at a constant speed in a uniform magnetic field. After adjusting the rotation speed of the coil, the image of the sinusoidal alternating current generated is shown in line B A. The instantaneous value of alternating current a is u = 10sin0.4 π TVC. The maximum value of alternating current B is 203vd. In the figure, the magnetic flux passing through the coil is zero at t = 0

A. According to the graph, if the period TA = 0.4s, TB = 0.6s, then the ratio of the two rotating speeds Na: NB = TB: TA = 3:2. So a is wrong. B. according to the graph, the maximum voltage um = 10V, the period TA = 0.4s, ω = 2 π t = 5 π rad / s, the instantaneous value expression of AC voltage is u = umsin, ω t = 10sin5 π TV

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