Glossary
Capacitance (C)
A quantitative measure of a capacitor's ability to store electric charge per unit of potential difference across its plates, measured in Farads (F).
Example:
A large capacitance value means the capacitor can hold a significant amount of charge for a given voltage, much like a large water tank can hold more water.
Capacitors
Devices designed to store electrical charge and energy in an electric field, acting as temporary energy reservoirs in circuits.
Example:
A camera flash uses a capacitor to quickly release a burst of light, providing instant illumination.
Dielectric
An insulating material placed between the conductive plates of a capacitor, which increases its capacitance by reducing the electric field strength for a given charge.
Example:
Inserting a dielectric like paper between aluminum foil plates can significantly boost a homemade capacitor's charge storage capacity.
Dielectric Material (κ)
The insulating substance placed between capacitor plates, characterized by its dielectric constant (κ), which indicates how much it increases capacitance compared to a vacuum.
Example:
Using a dielectric material with a high kappa value, such as certain ceramics, allows engineers to design much smaller capacitors for the same required capacitance.
Electric Field (E)
A vector field that describes the force exerted on a test charge at any given point; in a parallel-plate capacitor, it is uniform between the plates.
Example:
The uniform electric field between the plates of a charged capacitor is responsible for accelerating electrons when the capacitor discharges.
Electric Potential Energy (U_C)
The energy stored within a capacitor due to the work done in separating charges and establishing an electric field between its plates.
Example:
The electric potential energy stored in a defibrillator's capacitor is what delivers the powerful, life-saving electrical shock to a patient's heart.
Gauss's Law
A fundamental law in electromagnetism that relates the electric flux through a closed surface to the net electric charge enclosed within that surface.
Example:
Gauss's Law can be applied to a Gaussian surface enclosing one plate of a capacitor to derive the magnitude of the electric field between the plates.
Parallel-plate capacitor
A common type of capacitor consisting of two parallel conducting surfaces (plates) separated by a small distance, often with a dielectric material in between.
Example:
Many electronic circuits, from computer motherboards to audio filters, utilize parallel-plate capacitors due to their simple construction and predictable behavior.
Permittivity of free space (ε₀)
A fundamental physical constant representing the ability of a vacuum to permit electric field lines, used in calculating capacitance and electric fields.
Example:
The permittivity of free space is a crucial constant in Coulomb's Law and Gauss's Law, underpinning calculations for electric forces and fields in a vacuum.
Plate Area (A)
The surface area of one of the conducting plates in a parallel-plate capacitor, directly proportional to its capacitance.
Example:
Increasing the plate area of a capacitor allows it to store more charge, similar to how a larger surface can accumulate more static cling.
Plate Separation (d)
The distance between the two conducting plates of a parallel-plate capacitor, inversely proportional to its capacitance.
Example:
Reducing the plate separation makes the electric field stronger for the same voltage, thereby increasing the capacitor's ability to store charge.