Superconductivity

Image Source: The Conversation

Practice Question: The technology in relation to ‘superconductivity’, in its current form  is not feasible for exploitation. What do you understand by ‘superconductivity’? Discuss the applications of and challenges in the implementation of this technology. – 250 words

Relevance – what is superconductivity?-application of superconductivity-challenges in relation to the exploitation of this technology.

What is Superconductivity?

Superconductivity is complete disappearance of electrical resistance in various solids when they are cooled below a characteristic temperature. This temperature (at which the resistance disappears), called the transition temperature, varies for different materials but generally is below 20 K (−253 °C).

What is a superconductor?

Due to absence of electrical resistance, a superconductor conducts electricity perfectly, meaning an electrical current in a superconducting wire would continue to flow round in circles for billions of years, never degrading or dissipating.

Applications of superconductivity.

Suggested uses for superconducting materials include medical magnetic-imaging devices, magnetic energy-storage systems, motors, generators, transformers, computer parts, and very sensitive devices for measuring magnetic fields, voltages, or currents. The main advantages of devices made from superconductors are low power dissipation, high-speed operation, and high sensitivity.

Superconducting magnets also made possible the recent detection of the Higgs Boson by bending and focusing beams of colliding particles.

The Meissner Effect

A superconductor is highly diamagnetic; that is, it is strongly repelled by and tends to expel a magnetic field. This phenomenon, which is very strong in superconductors, is called the Meissner effect.

When a superconductor is cooled below the critical temperature in the presence of a magnetic field, it suddenly expels the magnetic flux from its insides below the critical temperature. This is because it turns into what is called a diamagnet at this temperature. A perfect diamagnet does not allow magnetic fields to penetrate its bulk.

What materials can be used as superconductors?

Hundreds of materials are known to become superconducting at low temperatures. Twenty-seven of the chemical elements, all of them metals, are superconductors in their usual forms at low temperatures and low (atmospheric) pressure. Among these are commonly known metals such as aluminum, tin, lead and mercury. Superconductivity is not exhibited by any of the magnetic elements chromium, manganese, iron, cobalt, or nickel.

Challenges in the widespread use of superconductors

What prevents more widespread use of these materials is the fact that the superconductors we know about operate only at very low temperatures. In the simple elements for instance superconductivity dies out at just 10 Kelvin, or -263 °C. In some of more complicated compounds, superconductivity may persist to higher temperatures, up to 100 Kelvin (-173 °C). While this is an improvement on the simple elements, it is still much colder than the coldest winter night in Antarctica.

Finding a material where superconductive properties can be used at room temperature is a challenging task. Turning up the temperature tends return a potentially superconductor material back to its metallic state.

In matters of practical application, Japanese engineers have experimented with replacing the wheels of a train with large superconductors that hold the carriages a few centimetres above the track. The idea works in principle, but suffers from the fact that the trains need to carry expensive tanks of liquid helium with them in order to keep the superconductors cold.

Many superconducting technologies will probably remain on the drawing board, or too expensive to implement, unless a room temperature superconductor is discovered. Equipment made with the high-temperature superconductors would also be more economical to operate because such materials can be cooled with inexpensive liquid nitrogen (boiling point, 77 K) rather than with costly liquid helium (boiling point, 4.2 K).

Sources: Britannica, The Conversation, The Hindu