Charge induced on dielectric slab||Force OF attraction on inserting a dielectric

Force On Dielectric Slab

The strength of electric filed in the charged and isolated capacitor is decreased when the dielectric slab is inserted. When the dielectric slab is inserted between the plates of a charged capacitor, electricfield produced due to induced charged, opposite to the external field.

A dielectric is inserted between the plates of an isolated fully-charged capacitor. The dielectric completely fills the space between the plates. The magnitude of electrostatic force on either metal plate decreases, as it was before the insertion of dielectric medium. Due to insertion of dielectric slab in an isolated parallel plate capacitor (the dielectric completely fills the space between the plates), the electrostatic potential energy of the capacitor decreases.

Force on Dielectric Due to Charged Capacitor

A parallel plate capacitor with a dielectric slab with dielectric constant k= 3 filling the space between the plates is charged to potential V and isolated. Then the dielectric slab is drawn out and another dielectric slab of equal thickness but dielectric constant k'= 2 is introduced between the plates. The ratio of the energy stored in the capacitor later to that initially is: