00:02
So because the inverse square nature of the electric field, any location where the field is zero must be closer to the weaker charge.
00:08
In this case, it's q2.
00:09
And you consider magnitude when it comes to charges, not just positive or negative.
00:15
So also in between the two charges, the fields due to the two charges are parallel to each other and cannot cancel.
00:22
Thus, the only place where the field can be zero are closer to the weaker charge q2, but not in between the two charges.
00:28
So the electric field here, e is going to be equal to k, which is 1 over 4 pi epsilon, not.
00:39
It's going to cancel, so we're not going to worry about that, really, times the magnitude of the charge q2 divided by the distance squared, which is x here, minus k times the charge q1, divided by d, the distance between them, plus x.
01:07
Squared and we want to know where the electric field is zero so this is going to be equal to zero.
01:13
Okay, so then we'll be fine that q2 magnitude here.
01:21
We're not considering positive or negative times d plus x squared is equal to charge q1 times x squared.
01:40
Therefore x is equal to the square root of the magnitude of q2 divided by the square root of q1 minus the square root, again magnitude of q2, times the distance between d.
02:15
So this comes out to equal 18 centimeters, and this is to the left of charge q2.
02:27
So this we can write left of charge q2.
02:40
And box that in as our solution for part a.
02:46
I'll start a new page for part b here.
02:53
So the potential due to the positive charge is positive everywhere, and the potential due to the negative charge is negative everywhere.
02:59
So since the negative charge is smaller in magnitude than the positive charge, any point where the potential is zero must be closer to the negative charge...