Question

Seven capacitors, a switch $S$ and a source of emf are connected as shown in the figure. Initially, $S$ is open and all capacitors are uncharged. After $S$ is closed and steady state is attained, the potential difference in volt across the plates of the capacitor $A$ is

• A. 12
• B. 15
• C. 17
• D. 19

Answer 1

Answer: (A)

The equivalent circuit is

Above circuit is equivalent to the following circuit :

If $q$ be the charge on each capacitor, then
$\frac{q}{21}+\frac{q}{7}+\frac{q}{28}+\frac{q}{3}+\frac{q}{7}=59$
or $q=84\mu C$
$\therefore$ Potential difference across
$A=\frac{q}{7}=\frac{84}{7}=12V$