Plan
1. Power of Gauss’ law : Calculating E field
for symmetric geometries
2. Comparison of three highly symmetric
cases
3. How to calculate E field, if the geometry
lacks a symmetry?
(Gauss’ Law, which will appear
in Ch. 23, is equivalent to
Coulomb’s Law.)
Comparisons
1. Outside a uniformly charged sphere or
1 q total
spherical shell:
E=
4πε0 r 2
2. Field due to a uniformly charged,
infinitely long (i.e., very long) line:
1 λ
E=
2πε 0 r
3. Field due to a charged plane:
σ
no distance dependence
E=
2ε 0
How to calculate E field, if the
geometry lacks a symmetry?
Numerically integrate dE produced by all
charge elements dq. (It is usually easier to
numerically compute the electric potential
V first and then E --- subject of Chapter
24.)