Question

In the given circuit if point $C$ is connected to the earth and a potential of $ +2000\,V $ 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 $B$
$V_{A B} =\frac{7500}{5}$
i.e., $V_{A}-V_{B} =1500\, V$
$\therefore 2000-V_{B} =1500$ or $V_{B}=500\, V$