The size (length) of the dipole is the distance between the point charges times the magnitude of the charges. This leads to another possible definition: an electric dipole moment is a vector pointing from a negative electric point charge to a positive electric point charge, where both charges are of the same magnitude. Where we used q 1 = −| q| and q 2 = | q|. The first moment of this charge distribution is Where the charges are of opposite sign and equal magnitude. The charge distribution is written in terms of Dirac delta functions In this definition a dipole is a vector depending on the characteristics of the charge distribution.Ĭombining the two definitions, one considers two point charges: q 1 at position r 1 and q 2 at position r 2. In physics, one meets the following related, but different, definition: an electric dipole moment (often briefly "dipole") of an electrostatic charge distribution ρ( r) is its first moment, R << R then, seen from the distance R, the dipolar charge distribution is a point dipole. In general one is interested in the electric potential field due to the dipolar charge distribution at a distance R from the midpoint of the dipole. Small is a relative concept and requires further specification. Usually it is added to this definition that the distance r between the two point charges is small-if this is the case the dipole is a point dipole. In chemistry, an electric dipole is a charge distribution consisting of two electric point charges of opposite sign and equal magnitude.
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