.M= HoN N2S 2R 4z×107×50×100×4×10 2×0.2 =6.28×106H 因dI/dt=-50A/s =-M-3.14x107 dt 2 0.2 4 10 50 100 4 10 7 4       = − −  H 6 6.28 10− =  因dI2 /dt =-50 A/s dt dI M 2  1 = − V 4 3.14 10− =  2 12 I M   = R N N S 2 0 1 2 =