JEE Main · 2024 · 31 Jan 2024 · Shift 2 · Solid State

Classifying the given conductivities (in $\mathrm{S}{\mathrm{m}}^{-1}$) at 298.15 K by typical ranges — conductors above roughly $1\mathrm{S}{\mathrm{m}}^{-1}$, insulators below about $10^{-8}\mathrm{S}{\mathrm{m}}^{-1}$, and semiconductors in between:

$2.1\times 10^3$, $1.2\times 10$, $3.91$, and $1.0\times 10^3$ all fall in the conductor range (4 values).

$1.0\times 10^{-16}$ is far below the insulator threshold.

$1.5\times 10^{-2}$ and $1\times 10^{-7}$ fall in the semiconductor range.

The number of conductors among the materials is 4.