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)

$60\,\mu F$

Answer 2

$C'=C_{1}+C_{2}+C_{3}$
$=20+20+20$
$=60\,\mu F$
$\frac{1}{C''}=\frac{1}{C'}+\frac{1}{60}$
$\frac{1}{30}=\frac{1}{C'}+\frac{1}{60}$
$\frac{1}{C'}=\frac{1}{30}-\frac{1}{60}$
$\frac{1}{C'}=\frac{2-1}{60}$
$\frac{1}{C'}=\frac{1}{60}$
$\Rightarrow$ $C'=60$