Electric dipole

Definition

An electric dipole consists of two equal and opposite charges separated by a small distance. It creates an electric field and has a dipole moment, which is a vector quantity pointing from the negative to the positive charge.

5 Must Know Facts For Your Next Test

1. The electric potential $V$ at a point due to a dipole is given by $V = \frac{1}{4\pi\epsilon_0} \frac{\mathbf{p} \cdot \mathbf{r}}{r^3}$, where $\mathbf{p}$ is the dipole moment and $\mathbf{r}$ is the position vector.
2. The electric dipole moment $\mathbf{p}$ is calculated as $q \times d$, where $q$ is the magnitude of one of the charges and $d$ is the separation distance between them.
3. The potential due to an electric dipole falls off as $1/r^2$, which is faster than that of a single charge (which falls off as $1/r$).
4. In an external uniform electric field, an electric dipole experiences a torque that tends to align it with the field direction.
5. The energy of an electric dipole in an external electric field $\mathbf{E}$ is given by $U = -\mathbf{p} \cdot \mathbf{E}$.

Review Questions

• What is the formula for calculating the electrical potential at a point due to an electric dipole?
• How does the potential due to an electric dipole vary with distance?
• What happens to an electric dipole placed in a uniform external electric field?

Related terms

Electric Field: A vector field around charged particles that represents the force exerted on other charged particles.

Dipole Moment: A measure of the separation of positive and negative charges in a system; mathematically defined as $\mathbf{p} = q \cdot \mathbf{d}$.

Coulomb's Law: $F = k_e \frac{|q_1 q_2|}{r^2}$, describes the electrostatic force between two point charges.