The electric dipole moment is a vector quantity whose magnitude is equal to the product of charge on one dipole and distance between them. Its direction is from - q to + q.
Electric dipole moment is a vector quantity. Derivation of electric field at a point of equatorial plane: Consider a point P on broad side on the position of dipole formed of charges + q and - q at separation 2l.
From figure,
∴ Resultant electric field at P is E = E1cosθ + E2cosθ
If dipole is infinitesimal and point P is far away, we have l < < r, so l2 may be neglected as compared to r2 and so equation (3) gives
i.e. electric field strength due to a short dipole at broadside on position
Its direction is parallel to the axis of dipole from positive to negative charge.
