PHYS 212 Lecture 3: Flux 1/25/17
Document Summary
Flux: electric field * area * cos of the angle between electric field and normal vector. Gauss"s law (one of maxwell"s equations) total flux through closed gaussian surface if g. s. has multiple faces (e. g. a cube), add all of the face"s fluxes to get total. Useful for finding if often written as . Symmetry gives us the direction of . Can make a g. s. that meets some combination of these: Perpendicular to (cid:1866) on faces where e isn"t constant. Justification of gauss"s law for a point charge, the electric field is a sphere. Surface area of a sphere = 4 r2. (cid:3046)(cid:3043) (cid:3032)(cid:3045)(cid:3032) = (cid:3045)(cid:3045)= (cid:2869)40(cid:3044)(cid:3045)(cid:3118)(cid:4666)4(cid:2024)(cid:1870)(cid:2870)(cid:4667)= (cid:3044)0 for a point charge with arbitrary g. s. Split g. s. into radial (flux is zero) and sphere (flux adds to (cid:3044)0) portions for multiple charges: find flux due to each field then superposition. (cid:1869)(cid:3032)(cid:3041)(cid:3030)(cid:3042)(cid:3046)(cid:3032)(cid:3031) (cid:3046)(cid:3043) (cid:3032)(cid:3045)(cid:3032)=(cid:3045)(cid:3119)(cid:3119) where a = the total radius of the sphere and r is the.
