Why non conducting sphere haive electric field inside?
Answers
Because it is charged spherical shell, the change is not there within the empty space enclosed by the shell. The symmetry of the problem suggests the spherical Gaussian surface inside the shell,centered at the center of the shell. ... Hence, electric field at each point of Gaussian surface is zero.
In electrostatics, we generally assume our conductors to be ideal. This indirectly assumes that charges have free mobility inside the conductor. You must remember that a system is more stable the lower its energy is. A system of free charges always tries to assume a configuration in which its potential is the lowest. (This configuration is achieved because of the interactions between the charges.) The lowest potential energy for a charge configuration inside a conductor is always the one where the charge is uniformly distributed over its surface. This is why we can assume that there are no charges inside a conducting sphere.
Also, the electric field inside a conductor is zero. (This, also, is because of the free movement of charges. If there was a net electric field inside, the charges would rearrange because of it, and cancel it out.) Using Gauss' law on a spherical surface that has the same center as your conductor, (but a radius that is smaller by an infinitesimal amount) you can conclude that the net charge inside the conductor is zero. Therefore, all the charge has to lie on the surface of the conductor. (As this is the only part of the conductor outside your Gaussian surface.)