Insulator (electricity)
Material that resists electric current flow.
An electrical insulator is a material in which electric current does not flow freely due to tightly bound electrons. Insulators have higher resistivity than semiconductors or conductors, and are used to support and separate electrical conductors without allowing current through themselves. Common examples include non-metals such as glass, paper, and PTFE.
- field
- Electrical engineering, physics
- known_for
- High resistivity, electrical insulation, breakdown voltage
- key_property
- Large band gap in electronic band theory
Lore & Background
Insulators are characterized by their high resistivity, which distinguishes them from semiconductors and conductors. The atoms of an insulator have tightly bound electrons that cannot readily move. A perfect insulator does not exist because even insulating materials contain small numbers of mobile charge carriers that can carry current. All insulators become electrically conductive when a sufficiently large voltage is applied, causing electrical breakdown at the breakdown voltage. This occurs when the electric field tears electrons away from atoms, leading to a chain reaction that fills the material with mobile charge carriers.
Reader's Guide
Insulators are essential in electrical equipment to support and separate conductors, preventing current from flowing to ground or causing short circuits. They are used in bulk as insulation for wiring and cables, and specifically as insulating supports for power distribution lines on utility poles and transmission towers. The most important insulation material is air, but a variety of solid, liquid, and gaseous insulators are also used. In electronic systems, printed circuit boards use nonconductive materials like epoxy plastic and fibreglass. In high-voltage systems, liquid insulator oil prevents arcs, while other materials include ceramic, glass, gas, and vacuum. Insulation materials that perform well at power frequencies may be unsatisfactory at radio frequency due to heating from dielectric dissipation.
Did You Know?
- A perfect insulator does not exist because even insulating materials contain small numbers of mobile charge carriers.
- All insulators become conductors at very high temperatures as thermal energy puts valence electrons into the conduction band.
- Electrical breakdown occurs when the electric field accelerates free charge carriers to knock electrons from atoms, creating a chain reaction.
- In certain capacitors, shorts between electrodes due to dielectric breakdown can disappear when the applied electric field is reduced.
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