An electric dipole is a system of two equal and opposite charges. Consider a dipole along the vertical axis with a positive charge at point M and a negative charge at point N, separated by distance d. What is the electric potential at point A at a distance r from the origin? The potential at point A is the algebraic sum of the potential due to both the charges. Here, the distance rAM can be rewritten using the Pythagoras theorem. If r is far greater than d, polar coordinates can be used. The terms from the expression can be rearranged by expanding the terms in the parentheses, and further neglecting the smaller terms gives the simplified expression for rAM. A similar analysis gives the expression for rAN. The binomial approximation simplifies these expressions further, and substituting them gives the electric potential due to an electric dipole. The electric potential decreases as the square of the r and depends on the dipole moment's direction, where the dipole moment is the charge multiplied by the separation between the charges.