In the circuit shown the cells $A$ and $B$ have negligibleresistances. For $V_{A}=12 \mathrm{~V}, R_{1}=500 \Omega$ and $R=100 \Omega$ the galvanometer $(G)$ shows no deflection. The value of $V_{B}$ is :

• A

  $4 V$
• Correct answer
  B

  $2 \mathrm{~V}$
• C

  $12 \mathrm{~V}$
• D

  $6 V$

Solution

Since deflection in galvanometer is zero so current will flow as shown in the above diagram. current, $I=\frac{V_{A}}{R_{1}+R}=\frac{12}{500+100}=\frac{12}{600}$ So $\quad V_{B}=I R=\frac{12}{600} \times 100=2 V$

Hence, the correct answer is option: 'B'.