Coulomb’s Law questions for AP Physics C; from College board.
Finding the Location of a Third Charge.
Question
Suppose we have two point charges a distance of
apart, one with on the left and another with . A third charge of is placed along the same line in a location where it will not be moved. Where can the charge be placed?
The charge will not move when all forces applied to it are net 0. In other words, all forces are equal.
Then we use Fundamental Law of Charges to determine which of the two is the best answer. Since opposite charges repel, it makes sense that the third charge would be away from the two charges, rather than in between. Therefore, we pick