How far the distances between test charges and another charges(test charge have no resultant force)?
There are two forces in the problem which you must calculate. The force from what we will call charge one which is the charge on the left of the test charge and the force between the test charge and charge 2 The electrostatic force is defined as F = k (Q1)q/(R1)r^2 where k is a constant, Q1 is charge one, and q is the test charge, and R1 is the distance between the two Since the test charge experiences no resultant force or no net force, it is stationary, that is to say that both forces we are considering are equal. So k (Q1)q/(R1)^2 = k (Q2)q/(R2)^2 it is given that Q1 = Q2, so you can eliminate them from both sides. You can also eliminate k and q from both sides. You are left with 1/(R1)^2 = 1/(R2)^2. obviously R1 = R2 so now that we have determined that the test charge is in the middle of the other charges, simply divide their distance by 2 to get (C) 15 cm. *It can also be concluded from our equivalence equation that the test charge can have any value since it cancels out on both s
