# insulator

(noun)

## Definition of insulator

A substance that does not transmit heat (thermal insulator), sound (acoustic insulator) or electricity (electrical insulator).

Source: Wiktionary - CC BY-SA 3.0

## Examples of insulator in the following topics:

• ### Dieletrics and their Breakdown

•  By definition, an insulator is unable to conduct electricity.
• Under certain conditions, however, a material that is an insulator can become a conductor.Eventually, exposing any insulator to increasing voltage will result in the insulator becoming conductive.
• This point (the minimum voltage for the insulator to become a conductor) is known as the breakdown voltage.
• ### Capacitors with Dielectrics

• This interruption can come in the form of a vacuum (the absence of any matter) or a dielectric (an insulator).When a dielectric is used, the material between the parallel plates of the capacitor will polarize.
• The capacitance for a parallel-plate capacitor is given by:$c= \frac {\epsilon A}{d}$where ε is the permittivity, A is the area of the capacitor plates (assuming both are the same size and shape), and d is the thickness of the dielectric.Any insulator can be used as a dielectric, but the materials most commonly used are selected for their ability to resist ionization.
• ### Conductors and Insulators

• An insulator is a material in which, when exposed to an electric field, the electric charges do not flow freely—it has a high resistivity.
• While there is no perfect insulator with infinite resistivity, materials like glass, paper and Teflon have very high resistivity and can effectively serve as insulators in most instances.
• When exposed to enough voltage, an insulator will experience what is known as electrical breakdown, in which current suddenly spikes through the material as it becomes a conductor.
• ### Convection

• Convection and InsulationAlthough air can transfer heat rapidly by convection, it is a poor conductor and thus a good insulator.
• The amount of available space for airflow determines whether air acts as an insulator or conductor.
• ### Parallel-Plate Capacitor

• The dielectric between the conductors is meant to act as an insulator, preventing charge from bridging the gap between the two plates.
• ### Parallel-Plate Capacitor

• Through simplification and substitution, this integral can be changed to:$V=\frac {\rho d}{\epsilon}=\frac {Qd}{\epsilon A}$Given that capacitance is the quotient of charge and potential:$C=\frac {\epsilon A}{d}$Accordingly, capacitance is greatest in devices with high permittivity, large plate area, and minimal separation between the plates.The maximum energy (U) a capacitor can store can be calculated as a function of Ud, the dielectric strength per distance, as well as capacitor's voltage (V) at its breakdown limit (the maximum voltage before the dielectric ionizes and no longer operates as an insulator):$U=\frac {CV^2}{2}=\frac {\epsilon A(U_dd)^2}{2d}=\frac {\epsilon AdU_d^2}{2}$
• ### Humans and Electric Hazards

• Usually the best way to help the victim is to give the fist a hard blow with an insulator or to throw an insulator at the fist.
• ### Polarization

• Dielectrics A dielectric is an insulator that can be polarized by an electric field, meaning that it is a material in which charge does not flow freely, but in the presence of an electric field it can shift its charge distribution.
• ### Back EMF, Eddy Currents, and Magnetic Damping

• There is no discernible effect on a bob made of an insulator.
• ### Resistance and Resistivity

• Loosely speaking, a metal has large numbers of "delocalized" electrons that are not stuck in any one place, but free to move across large distances, whereas in an insulator (like teflon), each electron is tightly bound to a single atom, and a great force is required to pull it away.