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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Jeff Phillips
Loyola Marymount University
Fall 2002