00:01
Here we're going to be looking at some things with two electrodes that form capacitor plates.
00:08
So if we looked at these edge on, they would just look like straight lines, like a typical capacitor symbol.
00:16
But i'm showing them sort of at an angle so we can tell that they are circular capacitor plates.
00:26
And we're going to go through a process to figure out the charge on the plate.
00:32
The electric field and the potential.
00:35
And what is important is the electrodes are going to stay connected.
00:46
Okay, so the process we're going to go through is starting with the capacitance, we will calculate it from the area and the epsilon knot over the spacing between the two plates.
01:02
Actually, let me call that delta x, just so it's a little bit clearer, delta x.
01:12
And epsilon zero is just a constant 8 .85 times 10 to the minus 12 ferrads per meter.
01:27
Okay, so we'll get it in units of capacitance.
01:30
So that's going to be our first step because we'll be changing those electrodes around.
01:35
The next step we're going to do is find the charge on the plates by simply taking c times the delta v across the plates.
01:52
Our next step will be to find the electric field is found from the potential difference across the plates divided by delta x.
02:05
And the last step is to find delta v.
02:08
And let me point out there's nothing we have to do there.
02:13
We're going to keep the electrodes connected.
02:17
And as long as nothing else is getting connected, that voltage difference is going to stay 13 .4 volts.
02:31
Okay, so let's dig in.
02:34
The first situation that we're going to look at, we'll call that b, is the plates are going to stay the same area.
02:42
So the diameter of the plates is going to stay 10 .7 centimeters.
02:51
And i neglected to mention that the area up here is pi times the radius squared for a circle.
03:02
So the radius is half the diameter.
03:05
And we want to get everything in terms of si units.
03:10
So this is going to be 0 .0.
03:16
0535, yeah.
03:25
And let's go ahead and figure out the area in square meters.
03:43
Okay, and the spacing between the plates, we are going to change that and make it 1 .08 centimeters.
03:54
So we'll get that into meters.
04:02
Yes, okay.
04:04
And now we can determine our first thing, which is the capacitance.
04:09
And we'll leave the units, but the capacitance should come out to be in faradays.
04:36
And that turns out to be 7 .37 times 10 to the minus faradays, which is reasonable for air gap capacitor.
04:52
They are typically in the very small pico faraday type range.
05:05
Okay.
05:08
So the next thing we can do is determine the q on the plates...