00:02
When trying to find the electric potential at a given point from multiple charges, it's important to remember that you can just find the individual contribution from each charge and then add up all those potentials.
00:17
What i mean by that is, so we have the basic formula for the electric potential due to a point charge.
00:24
You might see it written out explicitly as 1 over 4 pi epsilon knot.
00:28
You might see it written out as just a k for the kulon constant.
00:31
Either way, the value is roughly 9 times 10 to the 9th, and then the units are newton, meter squared, per kulam squared.
00:40
And that'll work out to give you electric potential when you multiply by point charge and divide by.
00:47
So what do i mean by the individual contribution? well, there's a charge here that is 40 .1 centimeters away from the point.
00:54
There's a charge here that is also 40 .1 centimeters away from the point.
00:58
And a third charge in the corner that is a little bit further away.
01:02
You can use our good old pythagorean theorem to find that.
01:06
But if i use each of these values in this equation here, i can get three different electric potentials, and then just add them all together, and that's the total potential there due to all three charges.
01:22
I think what can trip people up pretty easily here is the units.
01:26
You need things in meters and couloms.
01:31
Things are given to us in centimeters and microcoolums.
01:35
So we just need to keep that in mind.
01:38
Let's do one of them real quick.
01:41
This is the potential at point a due to this charge.
01:44
It's a very large number.
01:46
It comes to about 345 .6 kilobolts.
01:49
And that comes about by our 9 times 10 to the 9 for our constant in the front.
01:55
This 15 .4 is going to be 15 .4 times 10 to the minus 6 because that's what micro means.
02:03
A microculom is 10 to the minus 6 coulomb.
02:08
And the distance are, that's going to be divided in there is 40 .1 centimeters or 40 .1 times 10 to the minus 2 meters.
02:20
If you plug that into a calculator, this is the number you're going to get...