When placed in an electric (E) or magnetic (B) field, equal but opposite forces arise on each side of the dipole creating a torque &tau: |
When placed in an electric (E) or magnetic (B) field, equal but opposite forces arise on each side of the dipole creating a torque τ: |
When placed in an electric (E) or magnetic (B) field, equal but opposite forces arise on each side of the dipole creating a torque τ:
which will tend to align the dipole with the field.
Strictly speaking a dipole contains only two point charges (or magnetic poles), however various arrangements of multiple charges have dipole moments and may be treated as an effective dipole. In these cases, the positive end of the dipole corresponds to the effective center of positive charge. Likewise, the negative end corresponds to the effective center of negative charge.
Many molecules have such dipole moments due to non-uniform distributions of positive and negative charges on the various atoms. For example:
(+ve) H-Cl (-ve)
A molecule with a permanent dipole moment is said to be polarised.
With respect to molecules there are three types of dipoles: