What is Electric Dipole?

Many objects found in nature can be successfully analyzed as isolated bodies having net charge, as we have done so far. Others show different kinds of behavior. One type of behavior is characteristics of an object that has no net charge but instead consists of equal positive and negative chares +q and –q separated by a fixed distance d. for example, an ionic molecule such as NaCl (in the high temperature vapor state, not the familiar crystalline from) is electrically natural but can be considered as a Na+ ion joined to a Cl-ion. For another example, a similar type of behavior of the water molecule is in part responsible for the large solubilities of many substances in water.

The configuration of two equal and opposite charges separated by a distance is called an electric dipole. In equation that describe electric dipoles, we find that the magnitude of the charge q on each of the components and their separation d often occur together as the product qd. It is convenient to define this quality as the electric dipole moment p.

P = qd

It turns out that quantity behaves like a vector. We define the vector electric dipole moment to have magnitude p = qd and a direction pointing from the negative charge to the positive charge along the line joining the two charges.

The electric dipole moment for a pair of opposite charges 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. Applications involve the electric field of a dipole and the energy of a dipole when placed in an electric field.