Question

Four condensers each of capacity $4\mu \text{F}$ are connected as shown in the figure. If $V_P-V_Q=15\text{V}$, the energy stored in the system is

• A. $2400\text{erg}$
• B. $1800\text{erg}$
• C. $3600\text{erg}$
• D. $5400\text{erg}$

Answer 1

The correct option is B $1800\text{erg}$


The net capacitance, $C_{eq}$ is given by,

$\frac{1}{C_{eq}}=\frac{1}{4}+\frac{1}{4+4}+\frac{1}{4}$
i.e. $C_{eq}=\frac{8}{5}\mu \text{F}$

Since, Energy is stored in the capacitor is given by,

$=\frac{1}{2}{C}_{eq}{V}^2$

$=\frac{1}{2}\times \frac{8}{5}\times 15\times 15\times {10}^{-6}$

$=180\times {10}^{-6}\text{J}$

$\because 1\text{J}={10}^7\text{erg}$

i.e. $180\times {10}^{-6}\times {10}^7=1800\text{erg}$