00:01
Okay, so we have a charged rod of length l with charged density lambda.
00:06
We want to figure out the electric field at a.
00:09
So here's what i'm going to do.
00:11
I'm going to take a little chunk of this.
00:17
The width of that chunk is dx.
00:20
The charge on that chunk is lambda dx, dq.
00:25
And then x is this distance.
00:33
All right.
00:34
And then the electric field at a is k -s -b, or d -a, d -e, is k -s -b -d -q, a plus l over 2 plus x, quantity squared.
01:09
And, of course, k -s -b, that's 9 times 10 to 9 ferrets per meter.
01:21
It's probably a better unit to use.
01:25
No, it's meters per ferret.
01:51
So there's our de.
01:54
And then our electric field, and by the way, this points in the negative i direction, as they all do.
02:04
So we don't have to actually worry about adding vectors.
02:11
So our electric field...