Perfect conductor
Encyclopedia
A perfect conductor is an electrical conductor
with no resistivity
. The concept is used to model systems in which the electrical resistance
or resistivity
is negligible compared to other effects. One such model is ideal magnetohydrodynamics, the study of perfectly conductive fluids. Another example is electrical circuit diagram
s, which carry the implicit assumption that the wires connecting the components have no resistance.
All known materials that are perfectly conductive also happen to be superconductors
. The latter, in addition to having no electrical resistance, exhibit quantum effects such as the Meissner effect
and quantization
of magnetic flux
through closed loops. The property of perfect conductance, together with the law of electromagnetic induction
, requires that the magnetic field inside a perfect conductor remain fixed, but according to classical electrodynamics it could have a nonzero, eternal value. In real superconductors, all magnetic flux is expelled during the phase transition to superconductivity, and the magnetic field is zero within the bulk of the superconductor (the Meissner effect).
A perfect conductor without the special quantum properties of real superconductors is known as a classical superconductor
, but that phrase is ambiguous as it is also used in some communities to distinguish between conventional superconductor
s and high-temperature superconductors. No such materials are known to exist, though the concept is a useful idealization of the low-resistivity case in many systems.
Electrical conductor
In physics and electrical engineering, a conductor is a material which contains movable electric charges. In metallic conductors such as copper or aluminum, the movable charged particles are electrons...
with no resistivity
Resistivity
Electrical resistivity is a measure of how strongly a material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electric charge. The SI unit of electrical resistivity is the ohm metre...
. The concept is used to model systems in which the electrical resistance
Electrical resistance
The electrical resistance of an electrical element is the opposition to the passage of an electric current through that element; the inverse quantity is electrical conductance, the ease at which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical...
or resistivity
Resistivity
Electrical resistivity is a measure of how strongly a material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electric charge. The SI unit of electrical resistivity is the ohm metre...
is negligible compared to other effects. One such model is ideal magnetohydrodynamics, the study of perfectly conductive fluids. Another example is electrical circuit diagram
Circuit diagram
A circuit diagram is a simplified conventional graphical representation of an electrical circuit...
s, which carry the implicit assumption that the wires connecting the components have no resistance.
All known materials that are perfectly conductive also happen to be superconductors
Superconductivity
Superconductivity is a phenomenon of exactly zero electrical resistance occurring in certain materials below a characteristic temperature. It was discovered by Heike Kamerlingh Onnes on April 8, 1911 in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum...
. The latter, in addition to having no electrical resistance, exhibit quantum effects such as the Meissner effect
Meissner effect
The Meissner effect is the expulsion of a magnetic field from a superconductor during its transition to the superconducting state. The German physicists Walther Meissner and Robert Ochsenfeld discovered the phenomenon in 1933 by measuring the magnetic field distribution outside superconducting tin...
and quantization
Quantization (physics)
In physics, quantization is the process of explaining a classical understanding of physical phenomena in terms of a newer understanding known as "quantum mechanics". It is a procedure for constructing a quantum field theory starting from a classical field theory. This is a generalization of the...
of magnetic flux
Magnetic flux
Magnetic flux , is a measure of the amount of magnetic B field passing through a given surface . The SI unit of magnetic flux is the weber...
through closed loops. The property of perfect conductance, together with the law of electromagnetic induction
Electromagnetic induction
Electromagnetic induction is the production of an electric current across a conductor moving through a magnetic field. It underlies the operation of generators, transformers, induction motors, electric motors, synchronous motors, and solenoids....
, requires that the magnetic field inside a perfect conductor remain fixed, but according to classical electrodynamics it could have a nonzero, eternal value. In real superconductors, all magnetic flux is expelled during the phase transition to superconductivity, and the magnetic field is zero within the bulk of the superconductor (the Meissner effect).
A perfect conductor without the special quantum properties of real superconductors is known as a classical superconductor
Classical superconductor
The phrase classical superconductor has two meanings depending on context.* In the context of classical electrodynamics or general physics: a perfect conductor with no special quantum mechanical properties...
, but that phrase is ambiguous as it is also used in some communities to distinguish between conventional superconductor
Conventional superconductor
Conventional superconductors are materials that display superconductivity as described by BCS theory or its extensions.Critical temperatures of some simple metals:ElementTc Al1.20Hg4.15Mo0.92Nb9.26Pb7.19...
s and high-temperature superconductors. No such materials are known to exist, though the concept is a useful idealization of the low-resistivity case in many systems.