Question

In the circuit shown below, the cells A and B have negligible resistance. For $VA_ = 12 V, R_1 = 500 \Omega$ and $R = 100 \Omega$, the galvanometer (G) shows no deflection. The value of $V_B$ is:

• A. $4\, V$
• B. $2\, V$
• C. $12\, V$
• D. $6\, V$

Answer 1

Answer: (B)

Applying Kirchhoff's law in loop 1 , we get, $500 I+$ $100 I=12$
So, $I=\frac{12 \times 10^{-2}}{6}=2 \times 10^{-2} A$
Hence, $V_{B}=100\left(2 \times 10^{-2}\right)=2 V$
Remember that at the condition of no deflection of galvanometer, there is no current through it.