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What is Superconductivity?

Published on 24/2/2012 & updated on Wednesday 16th of May 2018 at 07:43:52 PM
Superconductivity was discovered by Dutch Physicist Heike Kamerlingh Onnes in 1911 in Leiden. He was awarded the Nobel Prize in Physics in 1913 for his low-temperature research. Some materials when they are cooled, below certain temperature their resistivity get abolished means they exhibit the infinite conductivity.
dutch physicist heike kamerlingh
The property / phenomenon of infinite conductivity in materials is called superconductivity.

The temperature at which the metals change from normal conducting state to superconducting state, is called critical temperature/transition temperature. An example of superconductors, is Mercury. It becomes superconductor at 4k. In superconducting state the materials expel the magnetic field. A transition curve for mercury is shown in figure below-

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What is Superconductivity?

superconductivity The transition from normal conducting state to superconducting state is reversible. Moreover, below critical temperature the superconductivity can be abolished either by passing sufficient large current through conductor itself or by applying sufficient strong external magnetic field. Below critical temperature/transition temperature, the value of current through conductor itself at which the superconducting state abolished is called critical current. As the temperature (below the critical temperature) reduces the value of critical current increase. The value of critical current increase with decrease in temperature. The value of critical magnetic field also depends on temperature. As the temperature (below the critical temperature) reduces the value of critical magnetic field increase.

Superconductor Metals

Some metals when they are cooled below their critical temperature exhibits the zero resistivity or infinite conductivity. These metal are called superconductor metals. Some metals showing superconductivity and their critical temperatures/transition temperature are listed in table below -
SLSuperconductorChemical SymbolCritical/Transition Temperature TC(K)Critical Magnetic Field BC(T)
1RhodiumRh00.0000049
2TungstenW0.0150.00012
3BerylliumBe0.026
4IridiumIr0.10.0016
5LutetiumLu0.1
6HafniumHf0.1
7RutheniumRu0.50.005
8OsmiumOs0.70.007
9MolybdenumMo0.920.0096
10ZirconiumZr0.5460.0141
11CadmiumCd0.560.0028
12UraniumU0.2
13TitaniumTi0.390.0056
14ZincZn0.850.0054
15GalliumGa1.0830.0058
16GadoliniumGd1.1
17AluminiumAl1.20.010
18ProtactiniumPa1.4
19ThoriumTh1.40.013
20RheniumRe1.40.030
21ThalliumTl2.390.018
22IndiumIn3.4080.028
23TinSn3.7220.030
24MercuryHg4.1530.040
25TantalumTa4.470.083
26VanadiumV5.380.031
27LanthanumLa6.00.11
28LeadPb7.1930.080
29TechnetiumTc7.770.040
30NiobiumNb9.460.820

Properties of Superconductors

The superconducting material shows some extraordinary properties. Some of these properties are listed below
  1. Zero electric resistance (infinite conductivity)
  2. Meissner Effect: Expulsion of magnetic field
  3. Critical Temperature/transition temperature
  4. Critical Magnetic field
  5. Persistent currents
  6. Josephson Currents
  7. Critical current

Applications of Superconductivity

In modern field of technology the superconductivity is widely used in different fields of technology. Some of these applications are listed below-
  1. Medical: MRI (Magnetic Resonance Imaging), Ultra-Low Field Magnetic Resonance Imaging (ULF-MRI), Magneto-encephalography (MEG) and Magnetic Source Imaging (MSI), Magneto-cardiography (MCG) etc.
  2. Electric field: Generators, motors, transformers, relays, magnetic energy storages (SMES), superconducting magnets, HTS Induction Heater, Fusion etc.
  3. Electronics: SQUIDS (superconducting quantum interference device), High Speed computing, Quantum computing, Sensors, filters, circuitry, radar etc.
  4. Transportation: Magnetically levitated trains, Marine Propulsion (magneto-hydrodynamic), Marine Propulsion (motor) etc.
  5. Physics: Particle Accelerators, Magnets, Plasma / fusion research etc.




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