Arrange the following materials in increasing order of their conducti…

The correct answer is Option (1) → A, D, C, B

Conductivity depends on the number of free charge carriers. At room temperature:

(A) Insulators: a very wide band gap, almost no free carriers (about \( 10^{-11} \) to \( 10^{-19}\,\mathrm{S\,m^{-1}} \))
(D) Intrinsic semiconductors: only thermally generated electron–hole pairs, a small number
(C) Extrinsic semiconductors: doping adds a very large number of extra carriers, raising the conductivity many times
(B) Metals: a huge density of free electrons (about \( 10^{2} \) to \( 10^{8}\,\mathrm{S\,m^{-1}} \))

So the increasing order is A, D, C, B.

NCERT (2026-27):
On the Basis of Conductivity – “… (i) Metals: They possess very low resistivity (or high conductivity).
(ii) Semiconductors: They have resistivity or conductivity intermediate to metals and insulators.
(iii) Insulators: They have high resistivity (or low conductivity).”

Extrinsic Semiconductor – “The conductivity of an intrinsic semiconductor depends on its temperature, but at room temperature its conductivity is very low. … When a small amount, say, a few parts per million (ppm), of a suitable impurity is added to the pure semiconductor, the conductivity of the semiconductor is increased manifold. Such materials are known as extrinsic semiconductors or impurity semiconductors.”