Gauss' law is a much simpler way of finding E than Coulomb's law in situations with a large amount of symmetry. Typically, the gaussian surface should have the same symmetry as the problem.

When Gauss' law is used to find E at a point:
The surface should contain the pont in question.

The field should be constant across the surface. (Where the surface is discontinuous, it should be 'piecewise constant' )
 
 

The surface should be chosen so that the field is always perpendicular to the surface.
 
 

E inside (in the interior of) a conductor is zero, so a gaussian surface that is contained in the conducting material surrounds a net charge of zero. This allows you to find the charge induced on conducting surfaces that enclose charged particles.
 
 

Things you should be able to do for the test:
 
 

1. Know how to charge objects by conduction and induction. Know the sign of the charge generated by rubbing various materials.
 
 

2. Use Coulomb's law to find F and E, (magnitude and direction) due to a distribution of point charges. (Or conversely, find the magnitude of point charges from F and E.)
 
 

3. Use Coulomb's law to find F and E, (magnitude and direction) due to a continuous distribution of charge.
 
 

4. Be able to sketch electric field lines, and interpret sketches of field line.
 
 

5. Be able to calculate electric flux through a surface due to an E field.
 
 

6. Be able to use Gauss' law to find flux.
 
 

7. Be able to use Gauss' law to find E.