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The ridges are used to add surface area, which improves the electrical resistance of the insulator. 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 ampacity of a conductor, that is, the amount of current it can carry, is related to its electrical resistance: a lower-resistance conductor can carry a larger value of current. The resistance, in turn, is determined by the material the conductor is made from (as described above) and the conductor's size.
In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field.When a dielectric material is placed in an electric field, electric charges do not flow through the material as they do in an electrical conductor, because they have no loosely bound, or free, electrons that may drift through the material, but instead they ...
There are, however, components of electrical circuits which do not obey Ohm's law; that is, their relationship between current and voltage (their I–V curve) is nonlinear (or non-ohmic). An example is the p–n junction diode (curve at right). As seen in the figure, the current does not increase linearly with applied voltage for a diode.
The electrical resistivity of a metallic conductor decreases gradually as temperature is lowered. In normal (that is, non-superconducting) conductors, such as copper or silver, this decrease is limited by impurities and other defects. Even near absolute zero, a real sample of a normal conductor shows some resistance. In a superconductor, the ...
A corona discharge is an electrical discharge caused by the ionization of a fluid such as air surrounding a conductor carrying a high voltage. It represents a local region where the air (or other fluid) has undergone electrical breakdown and become conductive, allowing charge to continuously leak off the conductor into the air.
Moisture analysis is used for early detection of this. Dielectric gases can also serve as coolants. Vacuum is an alternative for gas in some applications. Mixtures of gases can be used where appropriate. Addition of sulfur hexafluoride can dramatically improve the dielectric properties of poorer insulators, e.g. helium or nitrogen. [2]
IEC 62219 Overhead electrical conductors – Formed wire, concentric lay, stranded conductors; IEC 62220 Medical electrical equipment – Characteristics of digital X-ray imaging devices; IEC TR 62221 Optical fibres – Measurement methods – Microbending sensitivity; IEC TR 62222 Fire performance of communication cables installed in buildings