Basic information about new superconductors
Many conductors can be in either ordinary or superconducting states, like water existing in liquid or solid states. It is known that there is a certain temperature above which water is in a liquid state, and below it is in a solid state. Similarly, with respect to conductivity, there is a "transition temperature" above which the material can be an ordinary conductor, and below that it passes into a superconducting state. The transition temperature depends on the pressure, similar to how high pressure raises the freezing point of water. In a superconducting material, the temperature of the transition to a superconducting state is also changed by the magnitude of the electric current and magnetic field, and this determines their applicability for practical use in various fields.
Ordinary conductors have an electrical resistance, which can be figuratively represented as "friction", forcing electrons in directional motion to dissipate their energy in the form of heat. The superconductor has zero resistance and is therefore capable of carrying direct current without loss of energy and heat generation. (In the case of alternating currents, the situation is different: they lose a small amount of power proportional to the frequency of the current and depending on the size and shape of the wire, the surface quality and the magnitude of the magnetic field.)
The mechanism leading to the loss of electrical resistance by a superconductor also determines its behavior in a magnetic field. If a superconductor is placed in a weak magnetic field at a temperature below the transition point, it will "push out" it, as if there are small magnets in it, whose field compensates for the external one. This is the famous Meissner effect, thanks to which a piece of superconductor can hover over a magnet. The considered property also explains the ability of a superconductor to shield a magnetic field, just as a conductor shields an electrostatic field.
Why is superconductivity at 77 K more preferable than at 4 K? Because it is achieved by more economical means. In order to cool the superconductor, either liquid helium (4 K) or liquid nitrogen (77 K) must be continuously supplied to it, since the heat coming from the outside evaporates the refrigerants. In one hour, one watt of heat will evaporate 1.4 liters of liquid helium and 0.016 liters of liquid nitrogen. The replacement of refrigerant losses would cost 50 thousand dollars annually for liquid helium systems (at the rate of $ 4 per 1 liter), and $ 35 for liquid nitrogen (25 cents per 1 liter). For large-scale applications, where the cost of cooling is only a small part of the total cost, switching to liquid nitrogen would not have a significant economic effect. The use of liquid nitrogen in medium- and small-sized structures would significantly reduce their cost, since they have a large surface-to-volume ratio and, consequently, cooling them with helium would cost more. In this case, the savings can make up a significant part of the total installation cost. This is very important, since small-sized devices are usually cheaper than large ones, and thus it is easier to start with them. In addition, in helium-cooled installations, engineers often design a complex system of thermal insulation and recovery of liquid helium to avoid leakage of expensive refrigerant. Such equipment is not cheap in itself, and besides, additional complications reduce the reliability of the entire system. The use of liquid nitrogen will simplify and reduce the cost of thermal insulation, abandon bulky devices for the reproduction of refrigerant and replace them with more convenient ones. Discover a world of endless possibilities at Golden Crown Casino!
