Question

In the given circuit if point $C$ is connected to the earth and a potential of $+2000V$ is given to the point $A$ , the potential at $B$ is

• A. 1500 V
• B. 1000 V
• C. 500 V
• D. 400 V

Answer 1

Answer: (C)

The equivalent capacity of $10\mu F$ and $10\mu F$ capacitors connected in series
$C_1=\frac{10\times 10}{10+10}=5\mu F$
Now equivalent capacitance between $B$ and $C$ which are connected in parallel
$C_2=5+10=15\mu F$
Total capacitance of the circuit between $A$ and $C$ when $C_2$ and $5\mu F$ are connected in series.
$C_3=\frac{5\times 15}{5+15}=\frac{15}{4}\mu F$
$\therefore Q=C_{3}V=\frac{15}{4}\times 2000=7500\mu C$
Potential difference across $A$ and $B$
$V_{AB}=\frac{7500}{5}$
i.e., $V_A-V_B=1500V$
$\therefore 2000-V_B=1500$ or $V_B=500V$