设两个半环式的螺线管的自感系数为L, L=2+2M L<L/2 E1=-(L+M,)=-(L+M) dt t (D′=,+M=)=-(L+M) dt dt E=61+2=-(2+2M)2比较:g=设两个半环式的螺线管的自感系数为L’ ， I I d t d I L M d t d I M d t d I (L ) ( )  1 = −  + = −  + d t d I L M d t d I M d t d I (L ) ( )  2 = −  + = −  + dt d I (2L 2M )  =  1 +  2 = −  + 比较： dt dI  = −L L = 2L + 2M L’< L / 2