# Gauss’ law

Gauss’ law

4E You have four point charges T q and -2q If possible describe how you would place a closed surface that encloses at least the charge 2q (and perhaps other charges) and through whichb the net electric flux is (a) O. (b) -r- 3qlEu’ and (c) -2qIE 5E A point charge of 1.8 p.C is at the center of a cubical Gausian surface 55 em on edge. What i the net electric flux through he surface? ssma buuerfly net  is in a uniform electric field of magnitude E. The rim. a circle of radius a. is aligned perpendicular to the field. Find the electric flux through the netting  Find the net flux through the cube given in Exercise 3 and if the electric field is given by (a) E = 3.00y] and (b) E = -4.ooi + (6.00 + 3.00.1’»).E is in newtons per coulomb and is in meters (c) In each case how much charge is enclosed by the cube.

When a shower b turned on in a closed bathroom, the splashing of the water on the bare tub can fill the room’s air with negatively charged ions and produce an electric field in the air as great as 1000 Ie. Consider a bathroom with dimensions of 2.5 m X 3.0 m x 2.0 m. Along the ceiling, floor and four walls approximate the electric field in the air as being directed perpendicular to the surface and as having a uniform magnitude of 600 e. Also treat those surfaces as forming a closed Gaussian surface around the room’s air What are (a) the volume charge density p and (b) the number of excess elementary charges e per cubic meter in the room 9P It is found expenmentally that the electric field in a certain region of Earths atmosphere is directed vertically down. At an altitude of 300 m the field has magnitude 60.0 N/C: at an altitude of 200 m. the magnitude  Find the net amount of charge contained in a cube 100m on edge. with horizontal face, at altitudes of 200 and 300 m Neglect the curvature of Earth. ism lOP -\t each pour on the surface of the cube show n in  the Clem field ” In the positive direction of z. The length of each edge of the cube is 3.0 111. On the top surface of the cube if   and on the bottom face of thc cube f = +20k N/e nocturne the net charge contained  the cube A charge If i, placed at one corner of a cube of edge  hat r the flux through each of the cube laces” (Hint. Use Gauss’la and symmetry argument.