A capacitor with square plates of length a on each side and plate separation d i

Question

A capacitor with square plates of length a on each side and plate separation d is charged with an external voltage source to a potential difference V, and then disconnected from the voltage source. Teflon is then inserted between the plates.

Part E - If the capacitor is once again connected to the voltage source, what is the difference between the energy density for the capacitor with the teflon between the plates and without the teflon?

Part F - With the capacitor still connected to the voltage source, what is the difference in charge that the plates can hold with and without the teflon?

PLEASE please all parts!

  E=20V^2/d^2     E=0V^2/2d^2     E=0V^2/d^2     E=0V^2/d^2     E=20V^2/d^2     E=0V^2/2d^2  

Explanation / Answer

partE

with out the teflon

E1 = (1/2)*c1*v^2

c1 = eo*A/d = eo*a^2/d

E1 = (1/2)*eo*a^2*v^2/d

after the teflon is inserted

E2 = (1/2)*c2*v^2

C2 = k*eo*a^2/d

k - dielectric constant of teflon = 2

E2 = 2*eo*a^2*v^2/2d = 2E1

difference = dE = E2 - E1

dE = 2E1 - E1

dE = E1 = eo*a^2*V^2/2d

+++++++++++++

part(F)

without the teflon

Q1 = C1*V = eo*a^2*V/d

with teflon

Q2 = C2*V = k*eo*A*V/d = 2*eo*a62/d = 2Q1

difference = Q2 - Q1 = Q1 = eo*a^2*v/d   <<-----answer

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