A parallel plate capacitor with plate area A and separation d is initially filled with a dielectric with a permittivity e = er*e0 (er > 1). You have charged up the plates, Q on top plate and -Q on bottom plate. If you pull out the dielectric, without disturbing the charge on the plates:
i) Will the electric field inside change (how much if yes)? Will the stored energy in the capacitor change (how much if yes)?
ii)If the original stored energy was 2x10-5 J and the work required to pull out the dielectric was 7x10-5 J, what is the relative permittivity er of the dielectric?