In general a topological insulator is a material that has gapped bulk, but conducting edge states that are protected by some symmetry. Can maybe someone confirm that this is indeed true? This means that every Chern insulator is a topological insulator, but not every topological insulator is a Chern insulator. Topological insulators is the bigger group and Chern insulator are a subgroup of that. Once the resistance is known, the voltage drop along a conductor and the power dissipated in it can be determined for any given current.I don't think the provided comment gives the right answer. The resistance of any conductor can be calculated from a knowledge of its cross-sectional area, its length, and the resistivity of the material. The field strength is simply the applied voltage divided by the insulator thickness. The field strength should always be lower than that which might cause insulator breakdown. The electric field strength is a measure of the electric stress set up in an insulator. It is seen that the air has the lowest breakdown voltage, at 30 kV/cm, and mica has the highest, at 2000 kV/cm. Table 1 lists typical breakdown voltages (or dielectric strengths) for various insulating materials. To help avoid breakdown, all insulating materials are rated according to the maximum voltage that may be safely applied. This is known as an insulator breakdown, and it normally results in the destruction of the insulator. If a sufficiently high potential difference is applied across an insulator, electrons can be pulled out of the atoms, and substantial current flow may occur. This is particularly evident with the porcelain insulators on high-voltage overhead cables during a rainstorm, when arcing occurs over the insulator surface. A current can also flow along the surface of an insulator, especially if the insulator is dirty or wet. In normal circumstances, this current is so small that it is absolutely negligible. Therefore, a very small electric current can flow through an insulator. In electronic equipment, flat cables of fine wires and thin printed circuit conductors are widely used.Įven in the best of insulating materials, there are some free electrons drifting about between the atoms. Sometimes there is more than one conductor, and these are, Of course, individually insulated.Ĭonductors employed for industrial and domestic purposes normally have stranded copper wires with rubber or plastic insulation. Electric cable usually consists of conducting copper wire surrounded by an insulating sheath of rubber or plastic. Insulatorsįigure 1 shows some typical arrangements of conductors and insulators. Once the resistance is known, the voltage drop along a conductor and the power dissipated in it can be determined for any given current. The best insulator materials have the highest breakdown voltage for a given thickness. The best conductor materials have the lowest resistivity, that is, resistance per cubic meter. Similarly, conductors may be destroyed if too much current is passed through them. Insulators may break down if subjected to excessive voltages.
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