00:01
So, first of all, we want to label a drawing of the electric field.
00:05
Okay, so let's figure this out.
00:06
So the plus side of the battery is here, the longer plate.
00:11
So that means that the plus side of the capacitor is the upper plate, the minus side is the lower plate.
00:19
Okay? electric field always goes from plus to minus.
00:29
Okay? so it goes in that direction, and it's a uniform field.
00:40
So basically we can think of it as being a bunch of equally spaced vectors.
00:49
So there's our electric field.
00:56
Okay.
00:57
So the distance between our plates is 10 centimeters.
01:02
That's the same thing as 0 .1 meters, and we need to be in meters, because we're automatically in mks units because it's an electricity problem.
01:12
Okay? we can figure out the magnitude of the electric field, because it's 900 volts divided by 0 .1 meters.
01:27
So that comes out to be 9 ,000 volts per meter.
01:41
Okay.
01:42
So we need that to do the next part.
01:45
So we're supposed to put in two points that we're going to label p and q.
01:53
So a, excuse me, a is two centimeters up here.
02:02
So here's my point a, and then point b is eight centimeters.
02:16
So a is two centimeters from p, and b is eight centimeters from p.
02:30
Okay? and so the work done, if i, we're going to take a charge, q is minus, so we get this formula.
02:52
Let's plug in the numbers...