(Wheatstone bridge) Show that if $R_{x} / R_{3}=R_{1} / R_{2}$ in the figure, then $I=0 .(R_{0}$ is the resistance of the . instrument by which $I$ is measured.) This bridge is a method for determining $R_{x^{\prime}} . R_{1}, R_{0}, R_{3}$ are known. $R_{3}$ is variable. To get $R_{n}$ make $I=0$ by varing $R_{3}$ Then calculate $R_{B}=R_{2} R_{1} / R_{2}$.