The correct sequence of conductivity of the following materials at 300 K in the increasing order is
(A) Copper
(B) Graphite
(C) Germanium
(D) Silicon
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (D), (C), (B), (A)
Materials are classed by their electronic conductivity. Metals such as copper have a large number of free electrons and the highest conductivity. Some non-metals, such as graphite, also conduct electronically, but much less than metals. Semiconductors such as silicon and germanium lie far below.
(A) Copper: a metal, 5.9 × 103 S m−1, the best conductor of the four.
(B) Graphite: a non-metal that conducts electronically, 1.2 × 10 S m−1.
(C) Germanium: a semiconductor, 2.0 S m−1.
(D) Silicon: a semiconductor, 1.5 × 10−2 S m−1, the poorest conductor of the four.
In increasing order of conductivity:
\( \displaystyle \text{silicon} \lt \text{germanium} \lt \text{graphite} \lt \text{copper} \)
Shortcut: Silicon is the lowest and copper the highest, so the order starts with (D) and ends with (A): Options (1) and (4). Germanium, a semiconductor, conducts less than graphite, so (C) comes before (B): Option (4).
NCERT (2026-27 edition):
Conductance of Electrolytic Solutions – …
