Question

In the following circuit diagram, the galvanometer reading is zero. If the internal resistance of cells is negligible then the value of x will be

• A. $10\Omega$
• B. $100\Omega$
• C. $200\Omega$
• D. $500\Omega$

Answer 1

The correct option is B $100\Omega$

Applying Kirchhoff's law for outer loop, $12-2=500I\Rightarrow I=\frac{10}{500}=1/50A$
As galvanometer reading is zero so the potential across resistance X is $IX=2$
or, $\left(1/50\right)X=2\Rightarrow X=100\Omega$