Assuming that the magnetic field intensity is B, the length of the conductor bar is L, the rotation angular velocity is W, and the induced electromotive force is ε, then the rotation angle is θ = WT after t seconds from 0, the change of magnetic flux is δ φ = B× δ S = B× L θ/2 = BLWT/2, and the induced electromotive force is ε = D φ/DT = δ φ/δ T = BLWT/2 ÷.