Capacitors and Dielectrics Lecture Notes

A comprehensive set of vocabulary flashcards covering the fundamental concepts of capacitors, including types, capacitance units, parallel plate mechanics, and dielectric properties.

Spherical-shaped single insulated conductor

A conductor rarely used to store electric charge as it has a limited capacity; adding charges increases the potential $V = \frac{1}{4\times \text{pi} \times \text{E}_. } \times \frac{Q}{r}$ until the electric field causes discharge through the surrounding air.

Capacitor

A device consisting of a pair (or more) of conductive parallel plates separated by an insulator, used for storing electrical charges and electrical energy.

Two parallel plates capacitor

The simplest and most commonly used form of capacitor, consisting of two plane and parallel conductors separated by a dielectric.

Two concentric cylinders capacitor

One of the various physical shapes a capacitor can take, consisting of two cylinders sharing a common center.

Two concentric sphere capacitor

A specific shape of capacitor featuring two spheres that share the same center point.

Capacitance ($C$)

The ratio of the charge ($Q$) stored on any of the plates to the potential difference ($\text{AV}$) between the plates, expressed by the formula $C = \frac{Q}{\text{AV}}$ and measured in farads ($F$).

Farad ($F$)

The unit of capacitance defined as the ability to store a charge of one coulomb with a potential difference of one volt between the two plates.

Microfarad ($μ F$)

A subunit of the farad equivalent to $10^{-6} \text{F}$, used because the farad is a very large unit for most practical applications.

Nanofarad ($nF$)

A subunit of the farad equivalent to $10^{-9} \text{F}$, used for practical capacitance measurements.

Picofarad ($pF$)

A subunit of the farad equivalent to $10^{-12} \text{F}$, used for measuring very small capacitance values.

Parallel plate capacitor

A system consisting of two identical, isolated, and parallel conductive plates of area ($A$) separated by a distance ($d$) and carrying equal but opposite charges.

Net charge ($Q_{total}$)

The total sum of charges on the plates of a charged capacitor, which is always zero ($Q_{total} = +Q - Q = 0$) because the plates hold equal quantities of opposite charges.

Uniform electric field

The regular field between parallel plates that occurs when the distance ($d$) is very short compared to the plate dimensions, allowing irregularity at the edges to be ignored.

Dielectric materials

Insulating materials that decrease the internal electric field when placed between capacitor plates, classified into polar and non-polar types.

Polar dielectrics

Materials like pure water whose molecules have permanent bi-polar electric moments and a constant distance between the centers of their positive and negative charges.

Non-polar dielectrics

Materials like glass and polyethylene whose molecules gain temporary bi-polar electric moments via electric induction and have a non-constant distance between charge centers.

Electric field ($E$)

The ratio of the potential difference ($\text{AV}$) between the two plates to the distance ($d$) between them, calculated as $E = \frac{\text{AV}}{d}$ and measured in $\text{volt/m}$.

Dielectric strength

The maximum amount of electric field a material can withstand before electrical breakdown occurs; it serves as a measure of the material's ability to withstand an applied electric field.

Dielectric constant ($K$)

Also known as relative permittivity, it is the ratio of the capacitance with a dielectric ($C_K$) to the capacitance in vacuum ($C$), expressed as $K = \frac{C_K}{C}$; it has no units.

Potential energy ($PE$)

The work stored in the electric field of a capacitor, calculated using the area of a triangle on a charge-potential graph: $PE = \frac{1}{2} Q \times \text{AV}$.

Power ($P$)

The rate at which energy is delivered or stored, calculated by the relation $P = \frac{PE}{t}$ and measured in watts ($\text{W}$).