Identify the incorrect statements in the following:
(A) When we heat a semiconductor, its resistance increases.
(B) When we heat a semiconductor, its resistance decreases.
(C) When we cool a semiconductor to 0 Kelvin, it becomes a superconductor.
(D) Resistance of a semiconductor is independent of temperature.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A), (C) and (D) only
In a semiconductor, heating breaks more covalent bonds and releases more electron-hole pairs. The number of charge carriers rises steeply with temperature, so the resistance falls as the temperature rises (a negative temperature coefficient of resistance).
(A) When we heat a semiconductor, its resistance increases. — Incorrect. Heating increases the number of charge carriers, so the resistance decreases. This is one of the incorrect statements.
(B) When we heat a semiconductor, its resistance decreases. — Correct. This follows directly from the increase in the number of electron-hole pairs.
(C) When we cool a semiconductor to 0 Kelvin, it becomes a superconductor. — Incorrect. At 0 K every valence electron is held in a bond and the conduction band is empty, so there are no free carriers. A pure semiconductor then behaves as an insulator, not as a superconductor. This is one of the incorrect statements.
(D) Resistance of a semiconductor is independent of temperature. — Incorrect. The resistance of a semiconductor depends strongly on temperature, as explained above. This is one of the incorrect statements.
NCERT (2026-27):
Temperature Dependence of Resistivity – “… Unlike metals, the resistivities of semiconductors decrease with increasing temperatures.”
Intrinsic Semiconductor – “… An intrinsic semiconductor will behave like an insulator at T = 0 K as shown in Fig. 14.6(a).”