Glossary
Capacitance (C)
A measure of a capacitor's ability to store electric charge, defined as the ratio of the charge stored on either plate to the potential difference between the plates.
Example:
A large capacitance value means the capacitor can store a significant amount of charge for a given voltage.
Capacitor
A device that stores electrical charge and potential energy, typically consisting of two conductive plates separated by a small distance.
Example:
A camera flash uses a capacitor to rapidly discharge stored energy, producing a bright burst of light.
Charge (Q)
A fundamental property of matter that causes it to experience a force when placed in an electromagnetic field. In capacitors, it refers to the amount of charge stored on one of the plates.
Example:
When you rub a balloon on your hair, you transfer charge, causing the balloon to stick to a wall due to electrostatic attraction.
Dielectric
An insulating material placed between the plates of a capacitor to increase its capacitance by reducing the electric field strength for a given charge.
Example:
Placing a ceramic dielectric between the plates of a capacitor allows it to store more charge at the same voltage.
Energy stored in a capacitor (U_c)
The potential energy stored in the electric field between the plates of a charged capacitor.
Example:
The flash in a camera discharges the energy stored in a capacitor to produce a bright light.
Farad (F)
The SI unit of capacitance, defined as one coulomb per volt (1 C/V).
Example:
A 1 Farad capacitor is quite large; most practical capacitors are measured in microfarads (µF) or nanofarads (nF).
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:
Using Gauss's Law, one can derive the electric field for symmetrical charge distributions, such as a charged sphere or an infinite line of charge.
Permittivity of free space (ε₀)
A fundamental physical constant representing the ability of a vacuum to permit electric field lines, used in calculating electric fields and capacitance in vacuum.
Example:
The permittivity of free space is a constant used in Coulomb's Law and the formula for parallel-plate capacitance in a vacuum.
Potential difference (V)
The work done per unit charge to move a test charge between two points in an electric field; also known as voltage.
Example:
A 9V battery creates a potential difference of 9 volts across its terminals, driving current in a circuit.