00:01
This question involves calculating the work done and moving a charge in an electric field made by other charges.
00:11
The nice thing about it is though is that to calculate work all we have to do is know what the potential difference is between the two points and we can multiply that times the charge that's being moved to get the work.
00:25
And the nice thing about potential is that it's a field.
00:31
So all you have to do is calculate what the potential is at each point by adding up algebraically the two potentials caused by each charge and then once you know the potential at each point we can find the potential difference and from that we can get the work.
00:48
So we proceed as follows.
00:50
The potential at point b is going to equal coulomb's constant k times q1 over r1, that's a distance from q1 to point b, plus coulomb's constant times q2, that's charge 2, divided by r2 which is a distance that r2 is away from point b.
01:24
So we can factor out the k here.
01:30
So this gives us k times q1.
01:34
Let's go ahead and start plugging in the numbers now.
01:38
Q1 is 10 times 10 to the minus 9 and the distance is 0 .08.
01:52
I'll leave off all the units here just to make it a little bit easier to read...