Superconductors are materials capable of leading to electricity, without offering any kind of resistance, as soon as they reach a temperature very low, known as the critical temperature. Also, make the lines of magnetic field not able to penetrate it, so superconductors can be used to promote magnetic levitation.
See too: Conductors and insulators - understand the differences and characteristics of each
How Superconductors Work
The phenomenon of superconductivity can only be explained by quantum physics. This phenomenon is characterized by the Meissner effect, which makes the magnetic field lines not able to penetrate the materials superconductors, if these materials are cooled to temperatures lower than their critical temperatures.
You first superconductors that arose needed to be refrigerated in extremely low temperatures. However, research into new materials has allowed them to be developed and able to exhibit superconductivity at higher temperatures. Recently, studies have shown that some materials can become superconducting in
temperatures very close to ambient, however, for this to occur, they need to be subject to pressuresmuchtall.
What is the relationship between superconductivity and temperature? Although the answer is not as simple as the question, let's try to understand it: metals in general are Goodconductors electricity, such as copper, silver and gold. Such ability is related to your measure of resistivity, what is extremelylow.
The low resistivity of metals, in turn, is related to the large quantity of electrons free, with the absence of impurities (in this context, impurities are atoms of other elements inside the conductor) and with the order of crystal structure, that is, the way the atoms they are positioned in relation to each other.
if heated, metals are not so good at conducting electrical current., by virtue of the increasegivesvibration of their atoms—the oscillation of these atoms causes more collisions with the electrons in the electric current, making it difficult to drive. However, if refrigerated, metals conduct even more easily than at room temperature, and, if we extrapolate this cooling, we will reach a point where there will be no resistance to the passage of electricity.
The reasoning related to the cooling of metals and the increase in conductivity was investigated by the Dutch physicist heikeKamerlinghonnes (1853-1926), by cooling a sample of mmercury at a temperature of -269 °C. At the time, Onnes realized that the resistivityof mmercury suddenlybecamenull when it reached that temperature.
About 20 years later, German physicists KarlMeissner and RobertOchsenfeld found that superconductors disrupted the passage of magnetic field lines within them.
In their experiments, they found that when a superconductor is exposed to an external magnetic field, electrical currents are formed on the outside, causing a magnetic field to appear on the surface of the superconductor that opposes the magnetic field. external. It is through this phenomenon, currently called the Meissner effect, that it is possible to make trains levitate, as is the case with maglev:
Types of superconductors and their materials
Superconductors are a class of materials that exhibit a change of state that causes them to transfer electrical charges without any opposition. As such, it is not possible to say what superconductors are made of, but rather the different materials used to make them. So, there are superconductors:
made of pure chemical elements, like mercury, the lead it's the carbon;
organic, such as fullerenes, carbon nanotubes, graphene;
ceramic;
made of different metal alloys, such as niobium-titanium, germanium-niobium.
See too: Electrical circuits – how they work, elements, electrical connections etc.
Technological Applications of Superconductors
Superconductors can be useful in any type of electrical circuit, in order to make it more efficient, however, while we do not have a conductor at room temperature, currently the main uses these are:
maglev trains – This type of train uses the Meissner effect present in superconductors to float, so it develops high speed and becomes more efficient than the conventional train.
Nuclear Magnetic Resonance Devices – Inside these devices, there are coils made of metallic alloys that, when cooled, become superconducting, being capable of producing high intensity magnetic fields.
Electricity production – In hydroelectric, thermoelectric, nuclear or even wind power plants, there is a need to convert mechanical energy in electrical, therefore, a generator is used, whose coils are made of superconducting metal alloys when properly colds.
By Rafael Hellerbrock
Physics teacher
Source: Brazil School - https://brasilescola.uol.com.br/fisica/os-supercondutores.htm
