Question

If the deflection of the galvanometer in the bridge circuit shown in the figure is zero, then the value of $R_x$ in ohms is_______$\Omega$.

• A. 33.33

Answer 1

The correct option is A 33.33

Since, current through the galvanometer is zero, thus $V_x=V_y,$ (no voltage drop so net current flow through galvanometer) is zero, circuit could be further simplified as

$V_A=\frac{\left(200||200\right)}{\left(200||200\right)+100}\times 2=1V$

$V_x=\frac{100}{100+100}{V}_A=0.5V$

$V_y=\frac{R_x}{R_x+100}\times 2$

$V_x=V_y$

Thus,
$\frac{1}{2}=\frac{2Rx}{100+Rx}$

$\therefore R_x=33.33\Omega$