a. Bạn tự vẽ sơ đồ mạch điện nha.
b. Ta có: \(I2=\dfrac{U1}{R1}=\dfrac{6}{5}=1,2A\)
\(\Rightarrow I_b=I1-I2=1,2-\dfrac{3}{3}=0,2A\)
\(\Rightarrow R_b=\dfrac{U2}{I_b}=\dfrac{3}{0,2}=15\Omega\)
c. \(R=p\dfrac{l}{S}\Rightarrow l=\dfrac{RS}{p}=\dfrac{25\cdot10^{-6}\cdot15}{1,10\cdot10^{-6}}=\dfrac{3750}{11}\left(m\right)\)