Question

Question #dbcca

Answer 1

The simple case of an electric dipole is when a positive charge and a negative charge separated by a distance `r` .

The electric dipole moment `vec mu or vec p`, is the product of the electric charge q and the distance `d` separating the two charges:
`vec mu = q*vec r`

`mu` is the dipole moment vector
`q` is the magnitude of the charge, and
`vec r` is the vector representing distance between the charges

When you have many charges, a dipole is a separation of the positive charges from the negative ones, you'll have two poles.

Here's an example :

The Oxygen is more electronegative so it'll pull the electrons toward it self, the electrons are negatively charged so you'll have a negative charge around the Oxygen `(-)` and the Hydrogen will have a small electron density around it `(+)` which forms an electric dipole.

The overall electric dipole moment is the vector addition of all the electric dipole moments :

another example :

Sources:
https://en.wikipedia.org/wiki/Electric_dipole_moment
https://en.wikipedia.org/wiki/Dipole
http://chemwiki.ucdavis.edu/Core/Physical_Chemistry/Atomic_Theory/Dipole_Moments