Question

The charge flowing through the cell on closing the key $k$ is equal to :

• A. $\frac{CV}{4}$
• B. $4CV$
• C. $\frac{4}{3}CV$
• D. $\frac{3}{4}CV$

Answer 1

The correct option is A $\frac{CV}{4}$

Before closing key K , the equivalent capacitance $C_{eq}=\frac{C(C+C+C)}{C+(C+C+C)}=\frac{3C}{4}$
charge flow $q=C_{eq}V=\frac{3}{4}CV$
After closing K, the equivalent capacitance $C_{eq}^{\prime }=C$ and charge flow $q^{\prime }=C_{eq}^{\prime }V=CV$
Thus net charge flowing $=q^{\prime }-q=CV-\frac{3}{4}CV=\frac{CV}{4}$