Question

câu 1

câu 2

câu 3

Answer 1

\(\dfrac{1}{R}=\dfrac{1}{R1}+\dfrac{1}{R2}+\dfrac{1}{R3}=\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{6}=1\Rightarrow R=1\Omega\)

\(\Rightarrow I=\dfrac{U}{R}=\dfrac{6}{1}=6A\)

Chọn B

Answer 2

Câu 2:

\(U=IR=0,6\cdot6=3,6V\)

Chọn A

Câu 3:

\(\left\{{}\begin{matrix}P=I^2R\\P'=\left(\dfrac{I}{4}\right)^2\cdot2R=\dfrac{1}{8}I^2R\end{matrix}\right.\)\(\Rightarrow P'=\dfrac{P}{8}\)

Chọn D