Transcript Chapter 23

23. Gauss’s Law
part(I)
Flux is represented by the number of electric field lines
penetrating some surface.
(a) Uniform field penetrating perpendicular surface: F = E A
(b) Uniform field penetrating surface at an angle: F = E A cos
q = E • A = En A
(c) Position dependent field: F = lim  Ei • DAi
(d) Flux through a closed surface:
Fc = § E • dA = § En A
Gauss’s law:
Fc = qin/eo
Applications:
•Spherical charge distribution/ spherical shell
•Cylindrically symmetric charge distribution
•Plane (infinite) sheet
24. Gauss’s Law
part(II)
Gauss’s law with conductors:
When there is no net motion of charge within the conductor, the
conductor is in electrostatic equilibrium.
A conductor in electrostatic equilibrium has the following
properties:
•The electric field is zero everywhere inside the conductor
•Any charge on an isolated conductor resides on its surface
•The electric field just outside a charged conductor is
perpendicular to the surface of the conductor and has a
magnitude s/e0
•On an irregularly shaped conductor, charge tends to accumulate
at locations where the radius of curvature of the surface is the
smallest; i.e., at sharp points.