Question

In the adjoining circuit, the battery $E_1$ has as emf of 12 volt and zero internal resistance, while the battery E has an emf of 2 volt. If the galvanometer reads zero, then the value of resistance X ohm is

• A. 300
• B. 100
• C. 500
• D. 200

Answer 1

The correct option is B 100

For zero deflection in galvanometer the potential different across X should be 2V
In this condition $\frac{12X}{500+X}=2$
$\therefore X=100\Omega$