Ta có:
$I_{1}=\dfrac{U_{V_{1}}}{R_{1}}=\dfrac{2}{R_{1}}$
$I_{V_{1}}=\dfrac{U_{V_{1}}}{R_{v}}=\dfrac{2}{R_{v}}$
$I_{2}=\dfrac{U_{V_{2}}}{R_{2}}=\dfrac{3}{2R_{1}}$
$I_{V_{2}}=\dfrac{U_{V_{2}}}{R_{v}}=\dfrac{3}{R_{v}}$
Ta có: $I_{1}+I_{V_{1}}=I_{2}+I_{V_{2}}$
$⇔\dfrac{2}{R_{1}}+\dfrac{2}{R_{v}}=\dfrac{3}{2R_{1}}+\dfrac{3}{R_{v}}$
$⇔\dfrac{1}{2R_{1}}=\dfrac{1}{R_{v}}$
$⇒\dfrac{R_{v}}{R}=2$