Arrange the following materials in the ascending order of their electrical conductivities.
A. Rubber
B. Iron
C. Carbon
D. Copper
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → A, C, B, D
Conductivity is the reciprocal of resistivity, so the material with the largest resistivity comes first. Approximate resistivities at room temperature:
\( \text{Rubber (A)}: \rho \sim 10^{13}\text{ to }10^{16}\,\Omega\,\mathrm{m} \text{ (insulator)} \)
\( \text{Carbon, graphite (C)}: \rho \approx 3.5\times10^{-5}\,\Omega\,\mathrm{m} \)
\( \text{Iron (B)}: \rho \approx 10\times10^{-8}\,\Omega\,\mathrm{m} \)
\( \text{Copper (D)}: \rho \approx 1.7\times10^{-8}\,\Omega\,\mathrm{m} \)
Increasing conductivity: Rubber < Carbon < Iron < Copper, that is, A, C, B, D.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), but it is still in the CUET 2026 syllabus, so do not skip it.
NCERT (Pre-rationalised edition, 2022-23):
Resistivity of Various Materials – …
