College Physics III – Thermodynamics, Electricity, and Magnetism
Definition
A dielectric is a non-conductive material that, when placed between the plates of a capacitor, increases its capacitance by reducing the electric field strength. This effect occurs due to polarization within the dielectric material.
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Dielectrics increase the capacitance of a capacitor by a factor equal to their dielectric constant (κ).
The dielectric constant is always greater than 1 for any material used as a dielectric.
When a dielectric is introduced into a capacitor, it reduces the potential difference for the same amount of charge stored.
Dielectrics can be solid, liquid, or gas and are chosen based on their dielectric strength and thermal stability.
Introducing a dielectric into an isolated capacitor (one not connected to a battery) decreases the voltage across its plates.
Review Questions
How does inserting a dielectric between the plates of a capacitor affect its capacitance?
What happens to the voltage across an isolated capacitor when a dielectric is introduced?
Why is the dielectric constant always greater than 1 for materials used in capacitors?
Related terms
Capacitance: The ability of a system to store an electric charge, defined as the ratio of stored charge (Q) to potential difference (V), given by $C = \frac{Q}{V}$.
Dielectric Constant: A dimensionless measure of how much an insulating material can increase the capacitance of a capacitor relative to vacuum; also known as relative permittivity.
Polarization: The alignment of dipole moments in an insulating material when exposed to an electric field, which reduces the overall field within the material.