Difference Between Superconductor and Perfect Conductor

Superconductor vs Perfect Conductor

Superconductors and perfect conductors are two widely used terms in electronics. These two phenomena are usually misunderstood as one. This article will try to remove the misunderstanding by presenting the similarities and differences between a superconductor and perfect conductor.

What is a Perfect Conductor?

Conductance of a material is directly connected with the resistivity of the material. Resistance is a fundamental property in the field of electricity and electronics. The resistance in a qualitative definition tells us how hard it is for an electrical current to flow. In the quantitative sense, the resistance between two points can be defined as the voltage difference that is required to take a unit current across the defined two points. Electrical resistance is the inverse of electrical conduction. The resistance of an object is defined as the ratio of the voltage across the object to the current flowing through it. The resistance in a conductor depends on the amount of free electrons in the medium. The resistance of a semiconductor mostly depends on the number of doping atoms used (impurity concentration). The resistance a system shows to an alternating current is different from that to a direct current. Therefore, the term impedance is introduced in order to make AC resistance calculations much easier. The Ohm’s law is the single most influential law when the topic resistance is discussed. It states that for a given temperature, the ratio of voltage across two points, to the current passing through those points, is constant. This constant is known as the resistance between those two points. The resistance is measured in Ohms. A perfect conductor is a material having zero resistance under any condition. A perfect conductor does not require any external factor to maintain the perfect conductivity. The perfect conductivity is a conceptual situation, which is sometimes used to ease the calculations and designs where the resistivity is negligible.

What is a Superconductor?

Superconductivity was discovered by Heike Kamerlingh Onnes on 1911. It is the phenomenon of having exactly zero resistivity when the material is under a certain characteristic temperature. Superconductivity can only be observed in certain materials. Theoretically, if the material is superconductive a magnetic field cannot be present inside the material. This can be observed by the Meissner effect, which is the complete ejection of magnetic field lines from the interior of the material as the material transfers to a superconducting state. Superconductivity is a quantum mechanical phenomenon and to explain the state of superconductor, knowledge in quantum mechanics is required. The threshold temperature of a superconductor is known as the critical temperature. When the temperature of the material is decreased pass the critical temperature the resistance of the material abruptly drops to zero. The critical temperatures of superconductors are usually below 10 Kelvin. High temperature superconductors, which were discovered more recently, can have critical temperatures as high as 130 Kelvin or more.