电磁感应习题三 r>R 时:4=B2xr=A=A一B=m r (r<r) B 8丌2R (r>r 8丌2r B 2nr= Po r2 B 2丌R 2电磁感应习题三 作者：杨茂田 2 0 2 2 r RI B  r =   r RI B =  2 0 2  Rr r r >R 时：   =  = l内 i l B d l B r I 2 0   I = 0 rI B 0 2   = = = 2 2 B w m  2 2 4 2 0 8 r RI  ( r  R ) 2 2 2 0 1 8 r I    (r  R ) I rr