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导电体[Electrical Conductor] [2005-4-18]
iamet 发表在 Ω〖物理〗
| An electrical conductor is a substance through which electrical current flows with small resistance. Metals are generally excellent electrical conductors. In the language of solid state physics, the electrons in conductors lie in a so-called "conduction band" that is directly on top of a so-called "valence band." Resistance increases with increasing temperature in conductors.
The boundary conditions satisfied at the surface of an electrical conductor are
   (1)
  (2)
  (3)
  (4)
in cgs, where  is the unit normal vector, E is the electric field, is the electrical conductivity, B is the magnetic field, c is the speed of light, and K is the surface current.
In MKS, the equations become
 (5)
(6)
(7)
 (8)
where  is the permittivity of free space and  is the permeability of free space.
In the interior of a solid electric conductor,
[img]http://scienceworld.wolfram.com/physics/eimg708.gif[img](9)
Similarly, inside a hollow conductor,
[img]http://scienceworld.wolfram.com/physics/eimg709.gif[img](10)
This means that the voltage  is constant throughout the conductor and equal to the value at the surface. Thus, a body surrounded by a conductor is shielded from external electric fields. This is the principle of the Faraday cage.
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