Insulator (electricity)

[[File:Insulator railways.jpg|thumb|Ceramic insulator used on electrified railways. The ridged shape increases the surface distance along which electrical leakage could occur, thereby enhancing the insulator’s effectiveness, especially in wet or polluted conditions.]]

[[File:Insulator railways.jpg|thumb|Ceramic insulator used on electrified railways. The ridged shape increases the surface distance along which electrical leakage could occur, thereby enhancing the insulator’s effectiveness, especially in wet or polluted conditions.]]

[[File:600V CV 5.5sqmm.jpg|thumb|Three-core copper wire power cable, each core with an individual colour-coded insulating sheath, all contained within an outer protective sheath]]

[[File:600V CV 5.5sqmm.jpg|thumb|Three-core copper wire power cable, each core with an individual colour-coded insulating sheath, all contained within an outer protective sheath]]

An '''electrical insulator''' is a material in which [[electric current]] does not flow freely. The atoms of the insulator have tightly bound electrons which cannot readily move. Other materials—[[semiconductor]]s and [[electrical conductor|conductors]]—conduct electric current more easily. The property that distinguishes an insulator is its [[resistivity]]; insulators have higher resistivity than semiconductors or conductors. The most common examples are [[Nonmetal (chemistry)|non-metals]].

An '''electrical insulator''' is a material in which [[elecmn/kkkkll,m,../nn

tric current]] does not flow freely. The atoms of the insulator have tightly bound electrons which cannot readily move. Other materials—[[semiconductor]]s and [[electrical conductor|conductors]]—conduct electric current more easily. The property that distinguishes an insulator is its [[resistivity]]; insulators have higher resistivity than semiconductors or conductors. The most common examples are [[Nonmetal (chemistry)|non-metals]].

A perfect insulator does not exist because even the materials used as insulators contain small numbers of mobile charges ([[charge carrier]]s) which can carry current. In addition, all insulators become [[electrically conductive]] when a sufficiently large voltage is applied that the electric field tears [[electron]]s away from the atoms. This is known as [[electrical breakdown]], and the voltage at which it occurs is called the [[breakdown voltage]] of an insulator. Some materials such as [[glass]], [[Electrical insulation paper|paper]] and [[polytetrafluoroethylene|PTFE]], which have high [[resistivity]], are very good electrical insulators. A much larger class of materials, even though they may have lower bulk resistivity, are still good enough to prevent significant current from flowing at normally used voltages, and thus are employed as insulation for [[Wiring|electrical wiring]] and [[Electrical cable|cables]]. Examples include rubber-like [[polymer]]s and most [[plastic]]s which can be [[thermosetting polymer|thermoset]] or [[thermoplastic]] in nature.

A perfect insulator does not exist because even the materials used as insulators contain small numbers of mobile charges ([[charge carrier]]s) which can carry current. In addition, all insulators become [[electrically conductive]] when a sufficiently large voltage is applied that the electric field tears [[electron]]s away from the atoms. This is known as [[electrical breakdown]], and the voltage at which it occurs is called the [[breakdown voltage]] of an insulator. Some materials such as [[glass]], [[Electrical insulation paper|paper]] and [[polytetrafluoroethylene|PTFE]], which have high [[resistivity]], are very good electrical insulators. A much larger class of materials, even though they may have lower bulk resistivity, are still good enough to prevent significant current from flowing at normally used voltages, and thus are employed as insulation for [[Wiring|electrical wiring]] and [[Electrical cable|cables]]. Examples include rubber-like [[polymer]]s and most [[plastic]]s which can be [[thermosetting polymer|thermoset]] or [[thermoplastic]] in nature.