Question

Find charge on positive plate of 8 $\mu F$ (assuming before connecting to battery all capacitors were uncharged)

• A. 36 $\mu C$
• B. 12 $\mu C$
• C. 24 $\mu C$
• D. 6 $\mu C$

Answer 1

The correct option is C 24 $\mu C$

Let s represent series and p represent parallel then to calculate effective capacitance, circuit can be represented by $\left\{12\mu F\right\}\left(s\right)\left\{8\mu F\right(p\left)40\mu F\right\}$
which is equivalent to $\left\{12\mu F\right\}\left(s\right)\left\{12\mu F\right\}$
$=6\mu F$
$\Rightarrow q_{\text{supplied}}=\text{Ceff}.\Delta V=6\times 6=36\mu C$
Now on $8\mu F\&4\mu F$ charge distributes propotional to their capacitance. Then charge on 8 $\mu F$ capacitor is given by
$q=\frac{4}{12}\times 36=24\mu C$