What is the correct sequence of conductivity when arranged in ascendin

What is the correct sequence of conductivity when arranged in ascending order?

Metals, semiconductors, insulators
Insulators, metals, semi-conductors
Semiconductors, metals, insulators
Insulators, semiconductors, metals
This question was previously asked in
UPSC CAPF – 2013
D) Insulators, semiconductors, metals
Electrical conductivity is a measure of a material’s ability to conduct electric current. Materials are classified based on their conductivity:
– Insulators have very low conductivity, resisting the flow of charge (e.g., rubber, plastic, glass).
– Semiconductors have conductivity between that of insulators and conductors, which can be significantly altered by temperature, doping, or external fields (e.g., silicon, germanium).
– Metals (conductors) have high conductivity, allowing charge to flow easily (e.g., copper, silver, gold).
Arranging these in ascending order of conductivity means starting from the lowest conductivity to the highest. Therefore, the correct sequence is Insulators < Semiconductors < Metals.
The conductivity of materials is related to the availability of free charge carriers (electrons or ions) within their structure and how easily these carriers can move. In metals, there is a large number of free electrons. In semiconductors, the number of free carriers is much smaller but can be increased. Insulators have very few free charge carriers.