1. The problem statement, all variables and given/known data Two point charges Q1= +5.00 nC and Q2 = -3.00 nC are seperated by 35.0cm. What is the electric potential at a point midway between the charges? 2. Relevant equations V = Ke(q/r), PE = Vq 3. The attempt at a solution This question is from Serway textbook. The answer is 103J/C. I understand the answer was obtained by Ke(5 nC- 3 nC)/ 17.5cm. But I wonder why do we subtract the two? Shouldn't we add them? For example, if +1charge were put at the mid point, the charge would feel both repelled and attracted by positive and negative charges, hence the summative force of the two. But the answer tells that the charge would have the potential energy that is partially cancelled out.