Question

Very fast conduction of electricity by matter is called superconductivity. This happens when the matter is:
(A) Dissolved in acids
(B) Cooled by very low temperatures
(C) Heated to high temperatures
(D) Treated with radiations

Answer 1

Hint: Superconductivity, one of the most exciting phenomena, was invented by physicist H. Kamerlingh Onnes. Super conductivity of a material can be described as the set of physical properties of that material such as the material will conduct electricity with no resistance and magnetic fields will be excluded from that material. The phenomenon of superconductivity is of great importance, as it will help us to design and develop power saving electronics.

Complete answer:
To answer this question, we need to first understand how a material becomes a superconductor and what property does a superconductor material possess.
Superconductivity is displayed by certain materials when they are cooled below a certain range of temperature and the temperature is known as superconducting critical temperature (). All known superconducting materials need to be cooled at very low temperatures, and must be below 125K.
A superconducting material is the material which offers no resistance to the charge moving through it. This means that a superconducting material will have zero resistance. The superconductors are able to completely exclude magnetic fields from them completely on passing current through it.
In the superconducting state of the material, there is no resistance to the current and hence, the material will not lose any current in the form of heat. This makes the superconducting materials energy efficient, only exception is the energy required to cool the material to reach their superconducting state.
The phenomenon of superconductivity was first explained satisfactorily by BCS theory, proposed by John Bardeen, Leon Cooper and John Schrieffer. As per BCS theory, electrons in the lattice of the superconducting material, at low temperature behave as a sea of electrons. On decreasing temperature further, electrons passing between two positively charged nuclei will create a wave of non-uniform charges by pulling the nuclei slightly towards the electrons. Similarly, neighbouring electrons will also be attracted towards positive nuclei and will follow the first electrons forming an electron pair. These electron pairs further behave in a complex manner and the material acts as a superconductor.
Therefore, very fast conduction of electricity by matter, called super conductivity happens when the matter is cooled by very low temperatures.

Therefore, option (B) is the correct option.

Note: The resistance exhibited by material in its normal conducting state and superconducting state is different.
The conductivity and resistivity of the material are related to each other as follows:
$conductivity \propto \dfrac{1}{{resistivity}}$
The main difference between a material in its superconducting and normal conducting state is the material will have zero resistance in its superconducting state and will possess a fixed amount of resistance in its conducting state. Also, the current will stop flowing in a normal conductor when the source of current is removed. That is not true in case of superconductors. In superconductors, the current will keep flowing even if the source of current is removed.