Superconductivity: History, Classification and Applications
Science & Technology › Materials Science, Nanotechnology and Robotics · Topic 15.1
Superconductivity is a state of some materials in which electrical resistance drops to exactly zero and magnetic fields are pushed out of the material when it is cooled below a critical temperature. It was discovered in 1911 by the Dutch physicist Heike Kamerlingh Onnes, who found that mercury lost all resistance at about 4.2 kelvin. In 1933 Meissner and Ochsenfeld showed the Meissner effect, the expulsion of magnetic field, and in 1957 Bardeen, Cooper and Schrieffer explained low temperature superconductors with the BCS theory. In 1986 Bednorz and Muller found high temperature superconductors in copper oxide ceramics. Superconductors are used in MRI machines, particle accelerator magnets, maglev trains, sensitive magnetic detectors and in fusion devices.
5 min read · UPSC Prelims · Science & Technology · Materials Science, Nanotechnology and Robotics
At a Glance
- Discovered 1911, Kamerlingh Onnes
- Key effect Zero resistance, Meissner effect
- Theory BCS, 1957
- High temperature 1986, cuprates
- Main use MRI and strong magnets
- Exam link UPSC Prelims, Science & Technology: Materials Science, Nanotechnology and Robotics
Where Does It Fit?
This is the first topic of the macro on materials, nanotechnology and robotics. It starts from the physics of matter at very low temperature, which links with later topics on nanomaterials and with the earlier macro on nuclear fusion. Previous topic: Digital Terrestrial Television Transmission System. Next topic: Nanoscience and Nanotechnology: Origin and Basic Concepts.
What Is Superconductivity and How Did It Develop?
| Milestone | Details |
|---|---|
| 1911 | Kamerlingh Onnes, at Leiden, found zero resistance in mercury at about 4.2 K, three years after he first liquefied helium. He received the Nobel Prize in 1913 |
| Zero resistance | A current once started in a superconducting loop can flow for a very long time without a power source |
| 1933: Meissner effect | A superconductor expels magnetic field from its inside, so it is a perfect diamagnet and not just a perfect conductor. This allows magnetic levitation |
| 1957: BCS theory | Electrons form Cooper pairs through lattice vibrations and move without scattering. Nobel Prize in Physics in 1972 |
| 1986: high temperature | Bednorz and Muller found superconductivity in a lanthanum barium copper oxide near 35 K. Nobel Prize in 1987 |
| 1987 | YBCO, an yttrium barium copper oxide, worked at about 93 K, above the 77 K boiling point of liquid nitrogen, which is far cheaper than liquid helium |
| Critical values | Superconductivity is lost above a critical temperature, a critical magnetic field or a critical current density |
What Are the Types and Applications of Superconductors?
- Type I: mostly pure metals such as lead, mercury and tin. They have one sharp critical field and complete Meissner effect, but a low critical field
- Type II: alloys and ceramics such as niobium-titanium and YBCO. They let magnetic flux enter in tiny vortices between two critical fields, so they work in strong fields and are used for magnets
- MRI: magnetic resonance imaging uses superconducting coils cooled by liquid helium to give strong steady fields
- Particle accelerators: the Large Hadron Collider uses thousands of niobium-titanium magnets at about 1.9 K
- Maglev trains: Japan’s SCMaglev uses superconducting magnets to levitate and move trains at very high speed
- SQUID: Superconducting Quantum Interference Device, which measures extremely small magnetic fields, used in medicine and geology
- Power: lossless cables, fault current limiters, motors and generators
- Fusion and quantum computing: tokamaks such as ITER use superconducting coils, and many quantum computers use superconducting circuits
What Else Should You Remember?
- Cooper pair: two electrons that are bound together at low temperature in the BCS picture
- Liquid helium and nitrogen: helium boils at 4.2 K and nitrogen at 77 K, so materials working above 77 K are cheaper to cool
- Room temperature claim: a 2023 claim of a room temperature superconductor called LK-99 was not reproduced by other laboratories
- Hydrides at high pressure: hydrogen sulphide showed superconductivity near 200 K under extreme pressure in 2015, but it needs very high pressure
- Iron-based superconductors: found in 2008, a second family of high temperature superconductors
- Magnesium diboride: a simple compound that is superconducting at 39 K, discovered in 2001
- Josephson effect: current tunnelling between two superconductors through a thin insulator, used in sensitive devices
- Quench: a sudden loss of superconductivity in a magnet, which releases heat and must be controlled
- Cryogenics: the science of very low temperatures, needed for all uses
- Levitation: a magnet floats above a superconductor because of the Meissner effect
- Superfluidity: a related state of helium at very low temperature where it flows without friction
- India: Indian institutions such as IISc, TIFR and BARC work on superconducting materials and magnets, and India supplies magnets and cryogenic equipment for global science projects like ITER and LHC
- ITER link: India is a member of the ITER fusion project, as in Nuclear Fission and Nuclear Fusion
- Energy saving: grids lose several percent of power as heat, which superconducting lines could cut
- Barriers: ceramics are brittle, hard to make into wires and need cooling
- Medical use: MRI is a major clinical use of superconductors
- Electronics: superconducting circuits may give very fast and low energy computing, as in Quantum Computing
Why Does It Matter for the Exam?
- Discovery: 1911, Onnes, mercury, 4.2 K
- Effect and theory: Meissner, BCS
- Types: Type I versus Type II
- Current affairs link: room temperature claims and fusion magnets
- Common errors: calling a superconductor just a perfect conductor or saying high temperature means above room temperature
As an analytical point, superconductors already power MRI and big science. A material working at room temperature and normal pressure would change energy transmission, transport and computing, but none has been confirmed.
Why Is This Topic Important?
- History 1911 to 1986
- Physics Meissner, BCS
- Uses MRI, LHC
What Came Next?
The next topic covers nanoscience and nanotechnology and their origin. Next topic: Nanoscience and Nanotechnology: Origin and Basic Concepts.
Key People and Terms
- Critical temperature Transition temperature
- Meissner effect Expulsion of magnetic field
- Cooper pair Bound electron pair
- Type II Mixed state superconductor
- SQUID Sensitive magnetic detector
- Cryogenics Very low temperature science
Exam Corner
Points to Remember
- Discovered 1911 in mercury at 4.2 K.
- Meissner effect: 1933; BCS: 1957.
- High temperature: 1986.
- Liquid nitrogen boils at 77 K.
- LHC magnets: about 1.9 K.
Do Not Confuse With
- Perfect conductor and superconductor Zero resistance only versus zero resistance plus field expulsion
- Type I and Type II One critical field versus two
- High temperature and room temperature Above 77 K versus about 300 K
Memory Hook
Eleven mercury, Meissner expels, BCS pairs, YBCO beats nitrogen.
Mains Angle
Questions ask for discovery, effects and applications. These points help.
- Physics Zero resistance
- Uses Medicine, science
- Limits Cooling
A Question You May Face
An original practice question, not a past paper question.
“What is superconductivity? Explain its types and applications and the challenges in using it widely.”
How to Answer
- Define Zero resistance.
- Types I and II.
- Uses MRI, LHC.
- Limits Cooling cost.
GS Relevance
Frequently Asked Questions
What is superconductivity?
Superconductivity is a state of some materials in which electrical resistance becomes exactly zero and magnetic field is expelled when they are cooled below a critical temperature. Current can then flow without any loss of energy, which makes strong magnets and efficient devices possible.
What is the Meissner effect?
The Meissner effect, found in 1933, is the expulsion of magnetic field from the inside of a material when it becomes superconducting. It shows that a superconductor is more than a perfect conductor, and it is the reason a magnet can float above a superconductor.
What is the difference between Type I and Type II superconductors?
Type I superconductors are mostly pure metals with a single low critical magnetic field, above which superconductivity is lost fully. Type II superconductors, such as niobium-titanium alloys and ceramic oxides, allow magnetic flux to enter in vortices and stay superconducting in much higher fields, so they are used in strong magnets.
What are high temperature superconductors?
High temperature superconductors are materials, mainly copper oxide ceramics found from 1986, that become superconducting at temperatures much higher than older metals, some above the 77 K boiling point of liquid nitrogen. They are still very cold by everyday standards, but cheaper to cool than helium.
What are the main uses of superconductors?
Superconductors are used in magnetic resonance imaging scanners, in the magnets of particle accelerators such as the Large Hadron Collider, in fusion devices, in sensitive magnetic detectors called SQUIDs, in maglev trains and in some power equipment. Their main limit is the cost and difficulty of cooling.
PYQ Practice — Statement Analysis
1 Superconductivity was discovered in mercury in 1911.
By Kamerlingh Onnes.
2 A superconductor expels magnetic field from its interior.
This is the Meissner effect.
3 BCS theory explains the Meissner effect for all ceramic superconductors.
It explained low temperature superconductors.
4 MRI scanners use superconducting magnets.
Cooled with liquid helium.
Past Mains Questions on This Topic
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