[2019EM/QUIZ-08]

Electrodynamics                                                Apr 19, 2019
                                     Quiz-VIII

Question 1:
A student was asked to find the electric field inside
a uniformly polarized sphere. The following answer was received.

Sample Answer:


The answer to the above question as given in Griffiths is

\(\vec{E}=-\frac{\vec{P}}{3\epsilon_0}\)

1. Give your comments why is this answer wrong?
2. Give a counter example showing that the conclusion arrived by the student is incorrect.
3. Give steps to derive the correct answer

Question 2:
Consider a parallel plate capacitor with plates having charges \(Q\) and \(-Q\). An insulating medium fills the region between the plates. Assuming that the linear dimensions of the plates are much larger than the separation between the plates, draw a diagram to show

1. the distribution of free charges on the plates.
2. distribution of the bound charges on the surface of the dielectric material.
3. Use Gauss law to obtain \(\vec{D}\). Use your result for \(\vec{D}\) and obtain \(\vec{E}\), the potential difference between the plates and the capacitance.