# Electric Dipole Moment

1. May 24, 2012

Hi friends as all know that the direction of electric dipole moment vector is from negative charge towards the positive charge. I am pretty confuse that this direction is allotted to the dipole moment vector with some reason or just by convention.

2. May 27, 2012

### Simon Bridge

Mostly by convention - it is done this way to make the signs consistent with the rest of physics.

3. May 29, 2012

### tiny-tim

yes, it seems anomalous …

the polarisation field P is the sum of the electric dipole moments p, and:

·E = ρtotalo
·D = ρfree
but
·P = -ρbound

because of that, we have D = eoE + P, making it looks as if D is the total electric field, instead of E

(also, it means that the energy of an electric dipole p in an electric field E is minus p·E)​

Last edited: May 29, 2012