(Ω)R=R1+Rab=2+=5(Ω)I2=I3=I4=I5=I1==0.2(A)答:支路电流I1为0.4A,支路电流I2、I3、I4、I5相等均为0.2A。5(La5D3005).如图D-3所示,已知R1=10Ω,R2=4Ω,R3=6Ω,I3=0.1A。求支路电流I1、I2各是多少?UAB是多少?图D-3答案:解:画等效电路图如图D-3′,由等效电路图可知电阻R2及R3上的电压为图D-3′U2=U3=I3×R3=0.1×6=0.6(V)I2===0.15(A)I1=I2+I3=0.15+0.1=0.25(A)U1=I1R1=0.25×10=2.5(V)则UAB=U1+U2=2.5+0.6=3.1(V)答:支路电流I1为0.25A,I2为0.15A,UAB为3.1V。6(La5D3006).如图D-4所示,已知R1=2Ω,R2=4Ω,R3=3Ω,R4=6Ω,R5=8Ω,I4=0.3A。求RAB、UAB、流经各电阻的电流I1、I2、I3、I5各是多少?图D-4答案:解:等效电路图如图D-4′所示,用电路图化简方法解。R12=R1+R2=6(Ω)图D-4′R1~3=R12∥R3==2(Ω)R1~4=2+6=8(Ω)因为R5=R1~4=8(Ω)RAB=R5==4(Ω)因为R5=R1~4则I4=I5=0.3(A)I=2I4=2×0.3=0.6(A)UAB=I×RAB=0.6×4=2.4(V)U3=UAB-U4=UAB-I4R4=2.4-0.3×6=0.6(V)I3===0.2(A)I1=I2=I4-I3=0.3-0.2=0.1(A)答:RAB为4Ω,UAB为2.4V,I1、I2为0.1A,I3是0.2A,I5为0.3A。7(La5D4007).如图D-5所示电路求R1电阻两端的电压U1是多少?图D-5答案:解:画等效电路图如图D-5′所示。图D-5′则U1=IR1=1×1=1(V)
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