Question

Four condenser each of capacity $4\mu F$ are connected as shown in figure $V_p-V_q=15$ volts. The energy stored in the system is

• A. $2400$ ergs
• B. $1800$ ergs
• C. $3600$ ergs
• D. $5400$ ergs

Answer 1

The correct option is B $1800$ ergs

The resultant capacitance is,

$\frac{1}{C}=\frac{1}{4}+\frac{1}{8}+\frac{1}{4}=\frac{5}{8}$

$C=\frac{8}{5}=1.6\mu F$

Energy stored in capacitor is,

$E=\frac{1}{2}C{V}^2$

$=\frac{1}{2}\times 1.6\times {10}^{-6}\times {15}^2$

$=0.8\times 225\times {10}^{-6}J$

$=1800erg$