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单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,【2-4】,【解】,(a),求各电路的等效电阻,R,ab,,其中R,1,=,R,2,=,1,,,R,3,=R,4,=2,,,R,5,=4,G,1,=G,2,=1S,。,R,1,R,2,R,3,R,5,R,4,a,b,(a),R,4,被短路,R,ab,=,R,1,R,2,R,3,+,R,5,【2-4】,【解】,(b),求各电路的等效电阻,R,ab,,其中R,1,=,R,2,=,1,,,R,3,=R,4,=2,,,R,5,=4,G,1,=G,2,=1S,。,R,3,G,2,G,1,R,4,a,b,(b),R,ab,=(,R,1,+,R,2,),R,4,+,R,3,两个电阻并联:,两个电导串联:,两个电阻串联:,两个电导并联:,【2-4】,【解】,(c),求各电路的等效电阻,R,ab,,其中R,1,=,R,2,=,1,,,R,3,=R,4,=2,,,R,5,=4,G,1,=G,2,=1S,。,R,1,R,2,R,4,R,5,a,b,(c),开关 S 接通或断开时,,R,5,上电流均为零,可开路或短路,R,3,S,R,1,R,4,=,R,2,R,3,,电桥平衡,R,ab,=(,R,1,+,R,3,)(,R,2,+,R,4,),若:,R,1,R,4,=,R,2,R,3,则:,I,5,=0,所以:,可将,R,5,开路,或,短路。,电桥平衡,桥形连接,惠斯通电桥,R,1,R,2,+,_,R,3,R,4,R,5,U,S,I,5,R,S,【2-4】,【解】,(d),求各电路的等效电阻,R,ab,,其中R,1,=,R,2,=,1,,,R,3,=R,4,=2,,,R,5,=4,G,1,=G,2,=1S,。,R,1,R,2,R,2,R,1,a,b,(d),R,1,R,2,=,R,1,R,2,,电桥平衡,R,ab,=,R,1,(,R,1,+,R,2,)(,R,1,+,R,2,),R,1,R,2,R,1,R,2,R,2,R,1,a,b,R,1,R,2,对角线支路,R,2,上电流为零,可开路或短路,c,d,R,cd,=,R,2,(,R,1,+,R,1,)(,R,2,+,R,2,),R,ac,=,R,ad,=,R,1,(,R,1,+,R,2,)(,R,1,+,R,2,),R,bc,=,R,bd,=,R,2,(,R,1,+,R,1,)(,R,2,+,R,2,),5,2,10,8,a,+,U,10,b,U,ab,4A,+,对图示电桥电路,应用,Y,等效变换,求:,(,1,)对角线电压,U,(,2,)电压,U,ab,【解】,图(1),由 图(2)得:,I,1,I,2,R,1,2,8,a,+,U,2,4,2,b,U,ab,4A,+,图(2),R,2,R,3,【2-8】,所以:,又因为:,所以:,2,2,4,8,a,+,U,2,b,U,ab,4A,+,图(2),I,1,I,2,R,3,+,u,S,R,2,0,u,10,i,1,+,u,c,R,4,图示电路中R,1,=,R,3,=,R,4,,,R,2,=2 R,1,,,u,c,=,4,R,1,i,1,,利用电源的等效变换求电压,u,10,。,【2-13】,【解】,R,1,图(1),在图(2)中:,所以:,i,c,3,i,1,+,+,u,S,0,u,10,i,1,R,R,1,图(2),+,由电压源变换为电流源:,转换,转换,由电流源变换为电压源:,R,1,R,2,i,1,i,1,试求图(a)和图(b)的输入电阻R,in,【2-15】,【解】,R,in,R,1,R,2,i,1,i,1,图(a),+,u,i,i,2,法一:利用加压法 得:,R,1,R,2,i,1,i,1,试求图(a)和图(b)的输入电阻R,in,【2-15】,【解】,R,in,图(a),法二:,设受控源的等效电阻为,R,eq,,则,+,R,3,R,1,R,2,+,u,1,u,1,图(b),R,in,+,u,1,R,3,R,1,R,2,+,u,1,【解】,(b)法一:利用加流法 得:,+,u,i,i,1,i,3,图(b),【解】,法二:,+,u,1,R,3,R,1,R,2,+,u,1,+,u,i,i,1,+,R,3,R,1,R,2,+,u,1,u,1,图(b),R,in,【解】,法三:,i,1,R,3,R,1,+,u,1,设受控电流源的等效电阻为,R,eq,,则:,通常有两种求输入电阻的方法:,加压法,加流法,+,u,R,i,i,a,b,u,S,+,+,u,R,i,a,b,i,i,S,
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