电工基础的题目:`````````````````````````````````````````````````````````````````````````````习题:在题图中,已知E=220v,R1=25Ω,R2=55Ω,R3=30Ω.求:(1)开关S打开时电路中的电流及电阻上的电压.(2)开关S合上后

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电工基础的题目:`````````````````````````````````````````````````````````````````````````````习题:在题图中,已知E=220v,R1=25Ω,R2=55Ω,R3=30Ω.求:(1)开关S打开时电路中的电流及电阻上的电压.(2)开关S合上后
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电工基础的题目:`````````````````````````````````````````````````````````````````````````````习题:在题图中,已知E=220v,R1=25Ω,R2=55Ω,R3=30Ω.求:(1)开关S打开时电路中的电流及电阻上的电压.(2)开关S合上后
电工基础的题目:`````````````````````````````````````````````````````````````````````````````
习题:
在题图中,已知E=220v,R1=25Ω,R2=55Ω,R3=30Ω.求:
(1)开关S打开时电路中的电流及电阻上的电压.
(2)开关S合上后,各电阻上的电压是增大还是减小,为什么?

电工基础的题目:`````````````````````````````````````````````````````````````````````````````习题:在题图中,已知E=220v,R1=25Ω,R2=55Ω,R3=30Ω.求:(1)开关S打开时电路中的电流及电阻上的电压.(2)开关S合上后
开关S打开时,R1、R2、R3处于串联状态,因此:
I=U/(R1+R2+R3)=220/(25+55+30)=2(A)
U1=I*R1=2*25=50(V)
U2=I*R2=2*55=110(V)
U3=I*R3=2*30=60(V)
开关S合上后:
R2处于短路状态,只有R1、R3处于串联状态,因此:
I=U/(R1+R3)=220/(25+30)=4(A)
U1=I*R1=4*25=100(V) 增大
U2=0(V)
U3=I*R3=4*30=120(V) 增大

开关S打开时:
I=U/(R1+R2+R3)=220/(25+55+30)=2(A)
U1=I*R1=2*25=50(V)
U2=I*R2=2*55=110(V)
U3=I*R3=2*30=60(V)
开关S合上后:
R2短路
I=U/(R1+R3)=220/(25+30)=4(A)
U1=I*R1=4*25=100(V) 增大
U2=0(V)
U3=I*R3=4*30=120(V) 增大