This preview shows page 1. Sign up to view the full content.
SUNY Geneseo, Department of Physics and Astronomy
Physics 125: Analytical Physics II
Types of Gauss’ Law Problems
There are a limited number of Gauss’ Law problems, and certain types of equations that will
always com up in each type.
Notation:
Below, I’ll always use
r
for the radius of the Gaussian surface, and use
a
for the radius
of physical charged objects.
It is rarely the case that you want
r
and
a
to be the same.
Problem Type
Charge
densities likely
to be involved
Conductor with Cavity
Always
use a Gaussian surface that passes through “the meat” of the conductor
(shape is unimportant), so that
0
enc
surrounded
inner surface
0
qQ
Q
ε
=Φ
= =
+
Likely
to want to use charge conservation on the conductor:
conductor
outer surface
inner surface
QQ
Q
=+
Q
,
σ
Spherical Symmetry
Always
use Gaussian surface (sphere with radius
r
), so that
()
2
00
e
n
c
4
E
rq
επ
=
Likely
to want to use some combination of the following to get
q
enc
2
4
qa
σπ
=
3
4
3
ρπ
⎛⎞
=
⎜⎟
⎝⎠
Q
,
,
ρ
Cylindrical Symmetry
(infinitely long)
This is the end of the preview. Sign up
to
access the rest of the document.
This note was uploaded on 05/22/2008 for the course PHYS 125 taught by Professor Iyer during the Spring '08 term at SUNY Geneseo.
 Spring '08
 IYER
 Physics, Gauss' Law

Click to edit the document details