U=0 2 59 35 S 5×24×1 5+24+1 35 78 7-2535 X一U 78 闪四 西南交通大学西南交通大学 2¢ 1 I & 2 I & 1 - 1¢ U1 & + 1Ω 2 5Ω 4Ω 2Ω a I & b I & 0 1 2 21 2 = = U U I Y & & & , 7 5 1 I I a & = & , 5 1 1 I I b & = & 1 1 78 35 I & = U& 令 U2 = 0 & S U I Y U 78 35 4 1 4 1 5 2 5 2 1 0 1 1 11 2 = + ´ + + ´ = = & = & & 2 1 1 1 78 18 78 35 35 7 25 ) 7 5 5 1 I & I & b I & a ( I & ´ U& = - U& - = - = - = S U I Y U 78 18 0 1 2 21 2 \ = = - & = & &