A parallel plate capacitor of capacitance C0 has plates of area A with separation d between them.When it is connected to a battery of voltage V0, it has charge of magnitude Q0 on its plates.It is then disconnected from the battery and the space between the plates is filled with a material of dielectric constant 3.After the dielectric is added, the magnitudes of the capacitance and the potential difference between the plates are:
A)C0, V0.
B)C0, V0.
C)C0, V0.
D)3C0, V0.
E)3C0, 3V0.

Question

A parallel plate capacitor of capacitance C0 has plates of area A with separation d between them.When it is connected to a battery of voltage V0, it has charge of magnitude Q0 on its plates.It is then disconnected from the battery and the space between the plates is filled with a material of dielectric constant 3.After the dielectric is added, the magnitudes of the capacitance and the potential difference between the plates are:
A)C0, V0. 
B)C0, V0. 
C)C0, V0. 
D)3C0, V0. 
E)3C0, 3V0.

Quizplus · Accepted Answer

The capacitance of a parallel plate capacitor is given by:
C = εA/d
where ε is the permittivity of the medium between the plates, A is the area of the plates, and d is the distance between them.

When the dielectric material of constant k = 3 is introduced, the capacitance becomes:
C' = kεA/d = 3εA/d = 3C
So the capacitance increases by a factor of 3.

The potential difference between the plates remains the same, as the battery was disconnected and the charge on the plates remained the same. Therefore, the answer is D) 3C0, V0.

A Parallel Plate Capacitor of Capacitance C0 Has Plates of Area