Question

The minimum value of effective capacitance that can be obtained by combining $3$ capacitors of capacitances $1pF$, $2pF$ and $4pF$ is

• A. $\frac{7}{4}pF$
• B. $\frac{4}{7}pF$
• C. $1pF$
• D. $2pF$

Answer 1

Answer: (B)

$\frac{4}{7}pF$

Minimum capacitance is obtained when these three capacitors are connected in series with each other.

Effective capacitance of series combination $\frac{1}{C_{eff}}=\frac{1}{C_1}+\frac{1}{C_2}+\frac{1}{C_3}$

$\therefore$ $\frac{1}{C_{eff}}=\frac{1}{1}+\frac{1}{2}+\frac{1}{4}$

$⟹$ $C_{eff}=\frac{4}{7}pF$