The Electrical dipole moment reference article from the English Wikipedia on 24-Jul-2004
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Electrical dipole moment

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In physics, the electric dipole moment for a pair of opposite chargess of magnitude q is defined as the magnitude of the charge times the distance between them and the defined direction is toward the positive charge.

It is a useful concept in atoms and molecules where the effects of charge separation are measurable, but the distances between the charges are too small to be easily measurable. It is also a useful concept in dielectrics and other applications in solid and liquid materials.