Question

Cho R₁ =R₂ = R₃ = R₄ = R₅ = R₆ = R₇ = R₈ có trị số  bằng R = \(21\Omega\)

Tính R_tđ trong AB các TH sau

a) K₁, K₂ đều mở

b)  K₁ mở , K₂ dóng

c) K₁ đóng. K₂ mở

d) K₁, K₂ đều đóng

 

Answer 1

R1=R2=R3=R4=R5=R6=R7=R8=21(om)

a, K1,K2 đều mở R7 nt R8 \(=>Rtd=R1+R2=42\Omega\)

b, K1 mở,K2 đóng  (R4 nt R5 nt R6)//(R7 nt R8)

\(=>RTd=\dfrac{\left(R4+R5+R6\right)\left(R7+R8\right)}{R4+R5+R6+R7+R8}=.,....\)

c,K1 đóng , K2 mở R3//(R1 ntR2)//(R7 nt R8)

\(=>\dfrac{1}{Rtd}=\dfrac{1}{R3}+\dfrac{1}{R1+R2}+\dfrac{1}{R7+R8}=>Rtd=.....\)

d, K1,K2 đóng R3 //(R1 nt R2) //(R4 nt R5 nt R6)//(R7 nt R8)

\(=>\dfrac{1}{Rtd}=\dfrac{1}{R3}+\dfrac{1}{R1+R2}+\dfrac{1}{R4+R5+R6}+\dfrac{1}{R7+R8}=>Rtd=....\)