Glossary
Capacitance (C)
A measure of a capacitor's ability to store electric charge, defined as the ratio of the charge stored on its plates to the potential difference across them.
Example:
A large capacitance value means a capacitor can store a significant amount of charge at a relatively low voltage, useful in power supplies.
Capacitance changes
The alteration in a capacitor's ability to store charge, specifically an increase, when a dielectric material is inserted between its plates.
Example:
Observing capacitance changes when different materials are placed between capacitor plates helps engineers select the best dielectric for specific electronic components.
Charge (Q)
A fundamental property of matter that causes it to experience a force when placed in an electromagnetic field, representing the amount of electricity stored.
Example:
When a capacitor is connected to a battery, charge accumulates on its plates, creating an electric field between them.
Dielectric breakdown
The point at which a dielectric material, subjected to a sufficiently strong electric field, loses its insulating properties and begins to conduct electricity.
Example:
If a capacitor is overcharged, it can experience dielectric breakdown, leading to a short circuit and potential damage to the device.
Dielectric constant (κ)
A dimensionless quantity that measures a material's ability to concentrate electric flux and increase capacitance, defined as the ratio of the material's permittivity to the permittivity of free space.
Example:
A capacitor filled with a material having a dielectric constant of 5 will have five times the capacitance compared to one with a vacuum.
Dielectrics
Materials that become polarized when placed in an electric field, enhancing a capacitor's ability to store charge by reducing the voltage between its plates.
Example:
The ceramic layer in a smartphone's tiny capacitor acts as a dielectric, allowing it to store more energy in a compact space.
Electric dipoles
A pair of equal and opposite charges separated by a small distance, which are created within a dielectric material during polarization.
Example:
Water molecules are naturally electric dipoles due to their bent shape and uneven charge distribution, which is why they align in an external electric field.
Electric field reduction
The phenomenon where the total electric field strength inside a dielectric material is decreased due to the opposing induced electric field.
Example:
The electric field reduction inside a dielectric allows a capacitor to withstand higher voltages before experiencing dielectric breakdown.
Induced electric field
An internal electric field created within a dielectric material due to its polarization, which opposes the direction of the external electric field.
Example:
When a capacitor is charged, the induced electric field within its dielectric reduces the overall field strength between the plates, preventing breakdown.
Permittivity (ε)
A measure of how an electric field affects, and is affected by, a dielectric medium, representing the material's ability to store electrical energy in an electric field.
Example:
Materials with high permittivity are excellent for use in capacitors because they can support stronger electric fields for a given charge.
Permittivity of free space (ε₀)
A fundamental physical constant representing the absolute dielectric permittivity of a vacuum, used as a baseline for comparing the permittivity of other materials.
Example:
In a vacuum, the electric field strength and capacitance calculations rely on the permittivity of free space, which is approximately 8.85 x 10⁻¹² F/m.
Polarization (in Dielectric Materials)
The process where bound charges within a dielectric material shift slightly in response to an external electric field, creating tiny electric dipoles.
Example:
When a strong electric field is applied to a piece of rubber, its molecules undergo polarization, with positive nuclei shifting one way and electron clouds the other.
Voltage (V)
The electric potential difference between two points, representing the work done per unit charge to move a test charge between those points.
Example:
The voltage across a capacitor determines how much electric potential energy is stored within its electric field.