Dipole moment

Definition

A dipole moment is a measure of the separation of positive and negative electrical charges within a system, indicating the polarity of a molecule. It is represented as a vector quantity with both magnitude and direction.

5 Must Know Facts For Your Next Test

1. The dipole moment is calculated as $\vec{p} = q \cdot \vec{d}$, where $q$ is the charge and $\vec{d}$ is the displacement vector between charges.
2. Dipole moments are measured in Debye units (D), where 1 D = $3.33564 \times 10^{-30}$ C·m.
3. In an electric field, a dipole experiences both a force and torque, aligning itself with the field direction.
4. The potential energy of a dipole in an electric field is given by $U = -\vec{p} \cdot \vec{E}$.
5. A molecule with a zero dipole moment is nonpolar, whereas one with a nonzero dipole moment is polar.

Review Questions

• What formula represents the calculation of a dipole moment?
• In what unit is the dipole moment typically measured?
• How does a dipole behave when placed in an external electric field?

Related terms

Electric Dipole:

A pair of equal and opposite charges separated by some distance.

Polar Molecule: A molecule with an uneven distribution of charge, resulting in a net dipole moment.

Torque on Dipole: The rotational effect experienced by an electric dipole when placed in an external electric field, given by $\tau = \vec{p} \times \vec{E}$.