If the net flux through a gaussian surface is zero, which of the following statements are true?
1) There are no charges inside the surface. 2) The net charge inside the surface is zero. 3) The electric field is zero everywhere on the surface.
The number of electric field lines entering the surface equals the number leaving the surface.
Statements (b) and (d) are true. Statement (a) is not necessarily true since Gauss' Law says that the net flux through the closed surface equals the net charge inside the surface divided by eo. For example, you could have an electric dipole inside the surface. Although the net flux may be zero, we cannot conclude that the electric field is zero in that region.
A spherical gaussian surface surrounds a point charge q. Describe what happens to the: flux through the surface if
1) The charge is tripled, 2) The volume of the sphere is doubled, 3) The shape of the surface is changed to that of a cube,
The charge is moved to another position inside the surface;
1) If the charge is tripled, the flux through the surface is tripled, since the net flux is proportional to the charge inside the surface 2) The flux remains unchanged when the volume changes, since it still surrounds the same amount of charge. 3) The flux does not change when the shape of the closed surface changes. 4) The flux through the closed surface remains unchanged as the charge inside the surface is moved to another position. All of these conclusions are arrived at through an understanding of Gauss' Law.
A solid conducting sphere of radius a has a net charge +2Q. A conducting spherical shell of inner radius b and outer radius c is concentric with the solid sphere and has a net charge –Q as shown in figure 4.18. Using Gauss’s law find the electric field in the regions labeled 1, 2, 3, 4 and find the charge distribution on the spherical shell.
نلاحظ أن توزيع الشحنة على الكرتين لها تماثل كروي، لذلك لتعيين المجال الكهربي عند مناطق مختلفة فإننا سنفرض أن سطح جاوس كروي الشكل نصف قطره r.