(20 14? As shown in the figure, the period of uniform rotation of a rectangular coil in a uniform magnetic field is 0.02 seconds, and the rotation axis O 1O2 is perpendicular to the direction of the magnetic field. A, the instantaneous expression from the vertical neutral surface is: i=Imcosθ, then the maximum current value is: im = icos θ = 10.5 = 2a, the effective current value is: I = im2 = 2a, and the electric power consumed by the coil is: P=I2rT=2×2×0.02=0.08J, so AB is an error.

C the maximum induced electromotive force is: Em=Imr=2×2V=4V, and the induced electromotive force in the coil at any time is: e=4cos2πTt=4cos 100πt(V).

When t= 1300s, e=2V, e = n △? △t，

Solution: △? △ t = en = 2 100 = 0.02 WB/s, so c is correct and d is wrong.

So choose: C.