Question

Answer 1

a, R1 nt R2=>I1=I2

\(=>Q=I1^2R1t1=\dfrac{U^2t1}{R1}=>R1=\dfrac{U^2t1}{Q}\)

tương tự \(=>R2=\dfrac{U^2t2}{Q}\)

\(=>\dfrac{U^2t}{Q}=\dfrac{U^2\left(t1+t2\right)}{Q}=>t=t1+t2=50'\)

b, r1 // R2(làm tương tự chỉ khác Rtđ)

\(=>Q=\dfrac{U^2.t1}{R1}=>R1=\dfrac{U^2t1}{Q}\)

\(=>R2=\dfrac{U^2t2}{Q}\)

\(=>\dfrac{.Q}{U^2t}=\dfrac{Q}{U^2t1}+\dfrac{Q}{U^2t2}=>\dfrac{1}{t}=\dfrac{1}{t1}+\dfrac{1}{t2}=>t=8'\)