00:01
In this problem, we have a sphere surrounded by a shell, and in this part of the problem, each of them carries positive 6 microcouple.
00:11
Part a requires us to draw the field lines, and to do that we need to follow two principles.
00:18
One of them is that field lines go from positive charges to negative charges.
00:25
So that means away from positive charges.
00:29
The second idea is that there cannot be field lines inside conducting materials.
00:39
That means that for the sphere our field lines have to start at the surface of the sphere and they have to point away from it.
00:48
And they also have to stop once they get to the shell because the shell is also a conducting material.
00:55
So we have them like that.
00:59
But it's not like these field lines disappear here.
01:02
They continue once they leave the shell.
01:08
So we have them like this.
01:11
But let's not forget that the shell also has some charge.
01:15
So that means that the shell is going to create its own field lines as well.
01:20
And since it has positive six columns as well, we need to draw four field lines, for additional field lines.
01:33
There we go.
01:34
Here we have our diagram.
01:37
Now for part b it is useful to look at a clean diagram once again.
01:43
And we also need to recall gosses law.
01:47
Gus's law states that the integral of the electric field times with respect to area is equal to the charge enclosed over permittivity of free space.
02:05
Now, if we don't have an electric field within the shell, then that means that there must be some charge canceling out the inner spheres charge.
02:19
So the inner spheres charge has positive microculems, 6 microculems.
02:33
That means that the inner portion of the shell must have negative 6 microculems so that they cancel out this inner positive 6.
02:45
Now in the outer portion, you must think, well, if we have positive 6 and we put positive 6, then they add up to 0...