Gauss' Law problem types and hints

Gauss' Law problem types and hints - SUNY Geneseo,...

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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 = = + 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)
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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.

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