Tóm tắt:
\(R_1
\) // \(R_2\) // \(R_3\)
\(U_{AB}=30V\\
R_2=30\Omega\\
R_3=10\Omega\\
I_{AB}=10A\\
R_1=?\Omega\)
Giải
Ta có R1 // R2 // R3
\(\Rightarrow\left\{{}\begin{matrix}U_1=U_2=U_3=U_{AB}=30V\\I_1+I_2+I_3=I_{AB}=10A\end{matrix}\right.\)
\(\Rightarrow U\left(\frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{R_3}\right)=I\\
\Leftrightarrow\frac{1}{R_1}+\frac{1}{30}+\frac{1}{10}=\frac{I}{U}=\frac{1}{3}\\
\Leftrightarrow\frac{1}{R_1}=\frac{1}{3}-\frac{2}{15}=\frac{1}{5}\\
\Rightarrow R_1=5\Omega\)
Vậy \(R_1=5\Omega\)
Chúc bạn học tốt !
