Question

Which flows from point A to B, when switch is closed.

Answer 1

Rearranging circuit as shown in fig;

$q=CV$

$C_{eq}$ of total circuit $=\frac{20}{7}\mu F$

$q=25\times \frac{20}{7}=\frac{500}{7}\mu C$

Now apply KVL;

$20=\frac{20\times 25}{7\times 5}+\frac{q_1}{2.5}$

$\Rightarrow q_1=\frac{100}{7}\mu C$

$\Rightarrow q_2=\frac{400}{7}\mu C$ - Charge flow from B to A

$\Rightarrow -\frac{400}{7}\mu C$ - Charge flow from A to B