In: Physics
What is the magnitude of the force per unit area between two infinite, uniformly charged plates with a surface charge density of +4.20
Consider an
infinite plane which carries the uniform charge per unit area
. Suppose that the plane coincides with the
-
plane (i.e., the plane which satisfies
). By symmetry, we expect the electric field on
either side of the plane to be a function of
only, to be directed normal to the plane, and to point
away from/towards the plane depending on whether
is positive/negative.
Let us draw a cylindrical gaussian
surface, whose axis is normal to the plane, and which is cut in
half by the plane--see Fig. Let the cylinder run from to
, and let its cross-sectional area be
. According to Gauss' law,
![]() therefore, ![]() so force F= Charge (q)* Electric Field (E). force per unit area (F/A)= q*E/A. F/A= (q/A)*E. F/A= ![]() -------------------------F/A=( ![]() For two plates of oppsite sign charge density, force is equal in magnitude but different in direction. Ans A) F/A=(4.20 |