00:01
Here we're going to use gauss's law to determine the electric field of an insulating shell that holds a negative charge on it.
00:11
That shell is spherical with radius, let's say, r.
00:16
And the idea in gauss's law is that the electric flux through a closed surface, which is almost never an integral that you want to do, but you use symmetry to simplify that.
00:33
However, that electric flux is proportional to the enclosed charge over epsilon not.
00:42
One of the consequences of galsa's law is that a sphere of charge, provided the charge, cannot move around easily, will behave as if it is a concentrated point charge at its center on the outside of, the sphere.
01:01
However, on the inside, i can draw a little gaussian surface on the inside of the sphere, and there is no enclosed charge.
01:14
So what that tells us is that when r is less than r, big r, the radius of the sphere, the radial electric field is zero.
01:29
When r is bigger than the radius of the sphere.
01:35
Basically, the radial electric field times 4 pi r squared...