Dielectric

Definition

A dielectric is an insulating material that increases the storage capacity of a capacitor by reducing the electric field within it. Dielectrics are characterized by their ability to be polarized in the presence of an electric field.

5 Must Know Facts For Your Next Test

1. Dielectrics increase a capacitor's capacitance by a factor called the dielectric constant, $\kappa$.
2. The dielectric constant $\kappa$ is always greater than 1 for any material used as a dielectric.
3. When inserted between the plates of a capacitor, a dielectric reduces the effective electric field, which allows more charge to be stored at the same voltage.
4. The energy stored in a capacitor with a dielectric is given by $U = \frac{1}{2} C V^2$, where $C$ is the capacitance and $V$ is the voltage across the capacitor.
5. Common materials used as dielectrics include glass, ceramic, plastic, and even air.

Review Questions

• What effect does inserting a dielectric have on the capacitance of a capacitor?
• How does the dielectric constant ($\kappa$) affect the storage capacity of a capacitor?
• Why does adding a dielectric reduce the effective electric field within a capacitor?

Related terms

Capacitance: The ability of a system to store charge per unit voltage; measured in farads (F).

Electric Field: A vector field that represents the force per unit charge exerted on a positive test charge at each point in space.

Polarization: The process through which dipole moments within dielectric materials align with an external electric field.