Superconductivity
Dr. B. Keshav Rao
Department of Applied Physics
Shri Shankaracharya Technical Campus-SSGI, Bhilai
,Outline
- Superconductivity
- Temperature dependence of resistivity
- Critical magnetic field and Critical current
- Meissner effect
- Isotope effect
- BCS theory (Qualitative)
- Type I and Type II- High TC superconductors
- SQUIDS and Applications
Reference: Superconductivity by Kshirsagar & Avadhanulu, Engineering Physics, S. Chand Publications 2
,Superconductivity: Introduction
It is a novel state of matter exhibited by many conductors when cooled below their
superconducting transition temperatures.
A superconducting material exhibits zero electrical resistivity and complete
diamagnetism. This state is influenced by temperature, magnetic field and current.
There exist critical values for these three parameters, above which values the material
passes into normal state.
The zero electrical resistivity of superconductors implies zero I2R losses and hence
electrical power can be transported over very large distances with undiminished strength
by superconducting cables.
The complete diamagnetism of superconductors causes a strong repulsion of magnets
from the vicinity of a superconductor.
This effect can be utilized in different areas of technology. Until recent times, the main
bottleneck in putting superconductors to practical use is the requirement of extremely
low temperatures of the order of 0 to 20 K.
Recent discoveries of ceramic high temperature superconductors raised the hopes of
making practical use of superconductors in a big way. 3
, The Discovery
In 1908, the Dutch physicist, Kammerlingh Onnes succeeded in his efforts to liquefy helium.
Gaseous helium turned into liquid helium at 4.2 K at atmospheric pressure.
Using liquid helium as the coolant, the variation of electrical resistance of metals at low
temperatures was studied by Onnes.
In the year 1911, Onnes discovered that the electrical resistance of highly purified mercury
dropped abruptly to zero at 4.15 K. He called it superconductivity, and the material is called a
superconductor.
Subsequently, superconductivity was discovered in lead, tin, zinc, aluminium, and other metals
as well as in a number of alloys.
Kammerlingh Onnes was honoured in 1913 with the Nobel prize in physics for his investigations
of matter at low temperatures.
Abrupt change in resistance of mercury at
liquid helium temperature
4
Dr. B. Keshav Rao
Department of Applied Physics
Shri Shankaracharya Technical Campus-SSGI, Bhilai
,Outline
- Superconductivity
- Temperature dependence of resistivity
- Critical magnetic field and Critical current
- Meissner effect
- Isotope effect
- BCS theory (Qualitative)
- Type I and Type II- High TC superconductors
- SQUIDS and Applications
Reference: Superconductivity by Kshirsagar & Avadhanulu, Engineering Physics, S. Chand Publications 2
,Superconductivity: Introduction
It is a novel state of matter exhibited by many conductors when cooled below their
superconducting transition temperatures.
A superconducting material exhibits zero electrical resistivity and complete
diamagnetism. This state is influenced by temperature, magnetic field and current.
There exist critical values for these three parameters, above which values the material
passes into normal state.
The zero electrical resistivity of superconductors implies zero I2R losses and hence
electrical power can be transported over very large distances with undiminished strength
by superconducting cables.
The complete diamagnetism of superconductors causes a strong repulsion of magnets
from the vicinity of a superconductor.
This effect can be utilized in different areas of technology. Until recent times, the main
bottleneck in putting superconductors to practical use is the requirement of extremely
low temperatures of the order of 0 to 20 K.
Recent discoveries of ceramic high temperature superconductors raised the hopes of
making practical use of superconductors in a big way. 3
, The Discovery
In 1908, the Dutch physicist, Kammerlingh Onnes succeeded in his efforts to liquefy helium.
Gaseous helium turned into liquid helium at 4.2 K at atmospheric pressure.
Using liquid helium as the coolant, the variation of electrical resistance of metals at low
temperatures was studied by Onnes.
In the year 1911, Onnes discovered that the electrical resistance of highly purified mercury
dropped abruptly to zero at 4.15 K. He called it superconductivity, and the material is called a
superconductor.
Subsequently, superconductivity was discovered in lead, tin, zinc, aluminium, and other metals
as well as in a number of alloys.
Kammerlingh Onnes was honoured in 1913 with the Nobel prize in physics for his investigations
of matter at low temperatures.
Abrupt change in resistance of mercury at
liquid helium temperature
4
