00:01
So in this question, we have the volume charge density inside of a solid sphere is row not r over a equals r row.
00:17
And we want the total charge for a.
00:21
So q is the integral of row dv, and then dv is, so it's going to be 4 pi r squared, dr.
00:34
So dv you can think of as concentric shells.
00:39
And we want to integrate that's our dv.
00:42
Maybe we want to multiply by row.
00:43
And then row i'm going to sub in here.
00:45
And i know this is like an unconventional order.
00:47
So sorry for the awkwardness.
00:50
So this is the integral that we want to do.
00:52
Let's take out the constants.
00:54
Keep it simple.
00:55
So we have 4 pi.
00:57
There's a constant.
00:58
And then row over a, row not over a.
01:01
And then we have r cubed dr.
01:06
And then the integral of r cubedy r is r to the fourth over four.
01:10
So that's going to cancel out this four over here.
01:14
Oh, yeah, and then r is going to go from zero.
01:17
What is the actual radius? oh, radius a.
01:21
So we're going to integrate from zero to a.
01:23
So then we're going to do pi, row not, a to the fourth, divided by a is a cubed.
01:36
And we want the electric field strength within this sphere as a function of the distance.
01:43
So in general for that e, we want the, you know the integral of e .da is q enclosed over epsilon knot.
01:55
And then in general, q enclosed, we're going to integrate.
01:59
We're kind of doing the same thing except for we don't integrate out to a.
02:03
We only integrate out to some r...