例: B 求:电动势 解:G0ab0=E0ab+60=- Φ =0 d × Eoab =-8b0 =E0b oB0b<0, 2 b→a→0 × 例: 例:求电动势 解:6w=,×B)-a b -[VBcos(-0dl, 2nx cos0 to -dx, dx 2n 33 例: B b a O 求:电动势 解: 0 dt d m OabO Oab bO Oab bO Ob b = 0 , 2 1 2 BOb a b a O O 例: V I M N V I M N MN MN 例:求电动势 V b l I 0 l a 解: V B dl b a L ab ( ) ( ) V b = , b aVBcos( )dl I V B B dl = , cos ( cos ) 2 0 cos 0 0 dx x I V l l l 0 l a = dx , x l l IV l 2 0 cos 0 0 x dx x