Question

A parallel plate capacitor filled with a medium of dielectric constant $10$ , is connected across a battery and is charged. The dielectric slab is replaced by another slab of dielectric constant $15$. Then the energy of capacitor will :

• A. increase by $50 \%$
• B. decrease by $15 \%$
• C. increase by $25 \%$
• D. increase by $33 \%$

Answer 1

Answer: (A)

$E \Rightarrow \frac{1}{2}( KC ) v ^{2}$
$\therefore \%$ change
$\Rightarrow \frac{\frac{1}{2} K _{2} CV ^{2}-\frac{1}{2} K _{1} CV ^{2}}{\frac{1}{2} K _{1} CV ^{2}}$
$=\frac{ K _{2}- K _{1}}{ K _{1}} \times 100$
$\Rightarrow \frac{15-10}{10} \times 100=50 \%$