Glossary
Capacitance (C)
The ability of a capacitor to store electrical charge per unit of voltage across its plates. It is measured in Farads (F).
Example:
If a capacitor has a high capacitance, it can store a large amount of charge even at a relatively low voltage, making it useful for energy storage applications.
Capacitor
A device that stores electrical charge and energy in an electric field. It typically consists of two conductive plates separated by an insulator.
Example:
A camera flash uses a capacitor to quickly release a burst of stored energy, illuminating the subject instantly.
Charging (capacitor)
The process where current flows into an initially uncharged capacitor, causing its voltage to increase exponentially over time until it matches the source voltage.
Example:
When you plug in a device, the power supply's filter capacitors undergo charging to smooth out the incoming electrical current.
Dielectric constant (κ)
A dimensionless quantity that quantifies how much a dielectric material increases the capacitance of a capacitor compared to a vacuum. It indicates the material's ability to store electrical energy in an electric field.
Example:
Water has a high dielectric constant, which is why it's often used in high-voltage applications where increased capacitance is desired.
Dielectrics
Insulating materials placed between the plates of a capacitor to increase its capacitance by reducing the electric field strength.
Example:
Many electronic components use ceramic or plastic as dielectrics to make capacitors more compact while still achieving high capacitance values.
Discharging (capacitor)
The process where current flows out of a charged capacitor through a resistor, causing its voltage to decrease exponentially over time.
Example:
After turning off a device, the internal capacitors undergo discharging, which is why you might hear a faint click or see an LED briefly flash as residual energy dissipates.
Energy stored in a capacitor (U)
The electrical potential energy stored within the electric field between the plates of a charged capacitor. It can be calculated using various formulas involving charge, voltage, and capacitance.
Example:
The amount of energy stored in a capacitor determines how bright a camera flash will be or how long a backup power supply can last.
Parallel Capacitors
Capacitors connected side-by-side across the same two points in a circuit, resulting in a total capacitance that is the sum of the individual capacitances.
Example:
To increase the total capacitance in a circuit, an engineer might connect several parallel capacitors, effectively adding their individual storage capacities.
Parallel-plate capacitor
The simplest type of capacitor, consisting of two flat, parallel conductive plates separated by a small distance.
Example:
When designing a simple circuit for a school project, you might start with a parallel-plate capacitor to understand the fundamental principles of charge storage.
Permittivity of free space (ε₀)
A fundamental physical constant representing the ability of a vacuum to permit electric fields. It is used in calculating the capacitance of a parallel-plate capacitor.
Example:
The value of permittivity of free space is crucial when calculating the theoretical capacitance of a capacitor in a vacuum, before considering any dielectric materials.
RC circuit
An electrical circuit consisting of a resistor and a capacitor connected in series, commonly used for timing and filtering applications.
Example:
A simple blinking LED light often uses an RC circuit to control the rate at which the capacitor charges and discharges, thereby setting the blink frequency.
Series Capacitors
Capacitors connected end-to-end in a circuit, resulting in a total capacitance that is less than the smallest individual capacitance.
Example:
If you connect two 10 µF capacitors in series capacitors, the total capacitance will be 5 µF, effectively halving the storage capacity.
Steady state
The condition in a DC circuit where a capacitor is fully charged, and no more current flows through it, causing it to act like an open circuit.
Example:
After a long time, an RC circuit will reach steady state, and the capacitor will hold a constant voltage equal to the source voltage.