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:
increase by \( 50\% \)
decrease by \( 15\% \)
increase by \( 25\% \)
increase by \( 33\% \)
