posted by Ann on .
Two charges, -37 µC and +3 µC, are fixed in place and separated by 2.8 m.
(a) At what spot along a line through the charges is the net electric field zero? Locate this spot relative to the positive charge. (Hint: The spot does not necessarily lie between the two charges.)
how many m from the positive charge, not between the two charges?
This question is pretty weird, but basically what you want to do is set these two charges up in an equation with the distance and have them equal to zero.
K(q_1)/(r+2.8)^2 - k(q_2)/r^2 = 0
q_1 - the first (negative) charge
q_2 - the second (positive) charge
r - this is the distance between the two charges where the net charge will equal zero
2.8 - this value will be different for other people I'm assuming, so it's just the original distance between the charges, so it basically stands for d.
At this point I'm hoping that you know how to solve for r using basic algebraic skills.
This is the right equation and I used it so it works. Also make sure you know that the spot is outside the two charges, not inside, which is why it's subtraction.
* As a side note, the K is Coulombs constant, however solving symbolically you will find that these will cancel
My final equation after all of this looked something like this:
sqrt(q_1/q_2) = 1 + d/r