Question

If the equivalent capacitance between $P$ and $Q$ of the combination of the capacitors shown in figure below is $30\mu F$ , the capacitor $C$ is

• A. $60\mu F$
• B. $30\mu F$
• C. $10\mu F$
• D. $5\mu F$

Answer 1

Answer: (A)

$C^{\prime }=C_1+C_2+C_3$
$=20+20+20$
$=60\mu F$
$\frac{1}{C^{\prime \prime }}=\frac{1}{C^{\prime }}+\frac{1}{60}$
$\frac{1}{30}=\frac{1}{C^{\prime }}+\frac{1}{60}$
$\frac{1}{C^{\prime }}=\frac{1}{30}-\frac{1}{60}$
$\frac{1}{C^{\prime }}=\frac{2-1}{60}$
$\frac{1}{C^{\prime }}=\frac{1}{60}$
$\Rightarrow$ $C^{\prime }=60$