V_r = Potential at distance r, from a point charge Q.

• The voltage in space around a charge Q is negative if Q is negative and positive if Q is positive. This means that the sign of the charge is import in calculating the potential of a set of charges.
  
  
• The potential is a scalar quantity, not a vector. Thus, the potential of a group of charges is just the mathematical sum of potentials due to each charge.

• In two-dimensions, the electric potential V(x,y) can be pictured as a surface where the potential is plotted along the z-axis. See Rotating Surface Plot of the Electric Potential of Two Point Charges QT Movie (100K)