The general form of Gauss’s law describes how a charge
creates an electric field in a material, as well as in vacuum.
It is
where ) # 1)0 is the permittivity of the material. (a) A
sheet with charge Q uniformly distributed over its area A is
surrounded by a dielectric. Show that the sheet creates a
uniform electric field at nearby points, with magnitude
E # Q /2A). (b) Two large sheets of area A, carrying opposite
charges of equal magnitude Q, are a small distance
d apart. Show that they create uniform electric field in
the space between them, with magnitude E # Q /A).
(c) Assume that the negative plate is at zero potential.
Show that the positive plate is at potential Qd/A).
(d) Show that the capacitance of the pair of plates is
A)/d # 1A)0/d.