Physics 201 Introduction to Electricity & Magnetism 

September 18 Gauss' Law  



Relationship between
flux and charge Gauss' Law
A few points to remember... Gauss' Law gives the relationship between the flux through a surface and the enclosed charge. (These Gaussian surfaces are imaginary surfaces that do not effect the physical system.) Gauss' Law is always true! But, it isn't always useful!
If the flux integral is difficult we don't want to bother with Gauss' Law.
The integral is easy if the electric field is perpendicular or parallel
to the normal of a surface. In other words, if there is significant
symmetry cylindrical, spherical or planar we can select the surface to
be the "right" shape.
Gauss' Law and Coulomb's Law are really the same
thing
Gauss' Law will help us to quickly calculate the
electric field in situations where there is symmetry. If we know
the charge distribution and it has some sort of symmetry to it (planar,
spherical or cylindrical), we can quickly find the electric field everywhere
without having to integrate the small "chunks" of charge (which is typically
a pain).


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