1. The problem statement, all variables and given/known data A dielectric of dielectric constant 3 fills three fourth of the space between the plates of a parallel plate capacitor. What percentage of the energy is stored in the dielectric? E(r) = 3, distance between plates = d, thickness (t) = (3/4) * d, C=capacitance of the capacitor, q= charge of the capacitor, V= potential difference, A =area of plates, E(0) = permittivity of free space 2. Relevant equations E = C(V^2)/2, C = E(0)A/( (d-t) + t/E(r) ), C= q/V 3. The attempt at a solution I solved this (sort of) as follows: The capacitance C' if there was no dielectric = E(0)A/ d The capacitance C with the dielectric = 2 E(0)/ d [ after giving t = 3/4 d and simplifying ] The energy E' in the absence of dielectric = C'(V^2)/2 The energy E in the presence of the dielectric = C(V^2)/2 = 2E' percentage of energy in dielectric = (2E' - E')/2E' * 100 = 50 % I don't know if this approach is correct. Please help.