Question

Answer 1

Sơ đồ mạch: `R_1 //// (R_2 nt R_3)`

`a)R_[tđ]=[R_1.(R_2+R_3)]/[R_1+R_2+R_3]=[30.(40+20)]/[30+40+20]=20(\Omega)`

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`b)U=U_1=U_[23]=60(V)`

`@I_1=[U_1]/[R_1]=60/30=2(A)`

`@I_[23]=[U_[23]]/[R_[23]]=60/[40+20]=1(A)=I_2=I_3`

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`c)U_3=I_3.R_3=1.20=20(V)`

Answer 2

Vì R1 // R2, R1//R3

=> 1/Rtđ=1/R1 + 1/R2 + 1/R3

<=> 1/Rtđ= 1/30 +1/40 + 1/20

<=>1/Rtđ = 13/120

=>Rtđ= 120/13=9.23 ôm