Login processing...

Trial ends in Request Full Access Tell Your Colleague About Jove

22.15: Electric Dipoles and Dipole Moment

JoVE Core

A subscription to JoVE is required to view this content. Sign in or start your free trial.

Electric Dipoles and Dipole Moment

22.15: Electric Dipoles and Dipole Moment

Consider two charges of equal magnitude but opposite signs. If they cannot be separated by an external electric field, the system is called a permanent dipole. For example, the water molecule is a dipole, making it a good solvent.

Theoretically, studying electric dipoles leads to understanding why the resultant electric forces around us are weak. Since electric forces are strong, remnant net charges are rare. Hence, the interaction between dipoles helps us understand electrical interactions in ordinary objects around us.

When a permanent dipole is placed in a uniform electric field, it experiences no net force. However, it orients itself along the field so that the positive charge end points toward it. This interaction between the dipole and the electric field can be scrutinized by calculating the net torque it experiences.

Simple vector algebra leads to an interesting observation. The net torque depends on a cross-product of a new vector, called the electric dipole moment, and the electric field. The dipole moment is proportional to the magnitude of each charge and the separation between them.

If a molecule has a large separation between its positive and negative charge centers, it has a higher dipole moment. If the charge separated is itself high, its dipole moment is larger.

The dipole moment points from the negative charge to the positive charge. In the absence of any other torque, the dipole rotates and aligns with the field. The observation implies that the potential energy is associated with the orientation of the dipole with respect to the external electric field.

Suggested Reading


Electric Dipoles Dipole Moment Permanent Dipole Water Molecule Solvent Electric Forces Net Charges Electrical Interactions Uniform Electric Field Net Force Positive Charge End Torque Vector Algebra Electric Dipole Moment Magnitude Of Charge Separation Of Charges Molecule Separation Higher Dipole Moment Negative Charge To Positive Charge

Get cutting-edge science videos from JoVE sent straight to your inbox every month.

Waiting X
Simple Hit Counter