Question

Giúp mik với ạ m.n

Answer 1

Bài 9:

\(MCD:R_1//R_2\)

\(\Rightarrow R=\dfrac{R_1R_2}{R_1+R_2}=\dfrac{30\cdot60}{30+60}=20\Omega\)

Ta có: \(U=U_1=U_2=IR=0,6\cdot20=12V\)

\(\Rightarrow\left\{{}\begin{matrix}I_1=\dfrac{U_1}{R_1}=\dfrac{12}{30}=0,4A\\I_2=\dfrac{U_2}{R_2}=\dfrac{12}{60}=0,2A\end{matrix}\right.\)

Ta có: \(I'=\dfrac{I}{3}=\dfrac{0,6}{3}=0,2A\)

\(\rightarrow I'=I_3=I_{12}=0,2A\)

\(\Rightarrow R_3=\dfrac{U_3}{I_3}=40\Omega\)