Electric dipole moment

Definition

An electric dipole moment is a measure of the separation of positive and negative charges in a system. It is a vector quantity with both magnitude and direction.

5 Must Know Facts For Your Next Test

1. The formula for electric dipole moment $\vec{p}$ is $\vec{p} = q \cdot \vec{d}$, where $q$ is the charge and $\vec{d}$ is the displacement vector between charges.
2. Electric dipole moments are important in calculating the electric potential generated by the dipole at any point in space.
3. The direction of the electric dipole moment vector points from the negative charge to the positive charge.
4. For a point on the axis perpendicular to the line joining two charges, the potential due to a dipole decreases as $1/r^2$, where $r$ is the distance from the dipole center.
5. In an external electric field, an electric dipole experiences a torque that tends to align it with the field.

Review Questions

• What is the formula used to calculate an electric dipole moment?
• How does an electric dipole orient itself in an external electric field?
• What is the relationship between distance and potential for points on an axis perpendicular to a dipole?

Related terms

Electric Potential: The work done per unit charge in bringing a test charge from infinity to that point in space.

Torque: A force that causes rotation; for an electric dipole, it aligns with an external electric field.

Vector Quantity: $A$ quantity having both magnitude and direction, such as force or velocity.