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$\text{Câu 4) C: $\frac{I2}{I1}$=$\frac{R1}{R2}$}$
$\leftrightarrow$ $\text{Có U1=I1.R1}$
$\leftrightarrow$ $\text{Có U2=I2.R2}$
$\rightarrow$ $\text{$\frac{I2}{I1}$=$\frac{R1}{R2}$}$
$\text{Câu 5) A: 0,6A}$
$\text{Có $\frac{U1}{U2}$=$\frac{I1}{I2}$}$
$\rightarrow$ $\text{$\frac{12}{24}$=$\frac{0,3}{I2}$}$
$\rightarrow$ $\text{I2=$\frac{0,3.24}{12}$=0,6A}$
$\text{Câu 6) D: 30$\Omega$}$
$\text{Có công thức: R=$\frac{U}{I}$}$
$\rightarrow$ $\text{R=$\frac{15}{0,5}$=30}$
#TRANPHAMGIABAO
