A parallel plate capacitor filled with a dielectric of relative permittivity 5 between its plates is charged to acquire an energy E and isolated. If the dielectric is replaced by another of relative permittivity 2, its energy becomes

Options

A. E
B. 0.4 E
C. 2.5 E
D. 6.25 E

Answer

( c)

Explanation

Energy of a Capacitor,
`E = q^(2)/2C rArr E alpha 1/c`
`E_(1)/E_(2) = k_(2)c/k_(1)c =k_(2)/k_(1)`
`E_(2) = 5E/2`
`E_(2) = 2.5E`