Which of the following has a negative value for temperature coefficient of resistivity?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Silicon
The temperature coefficient of resistivity is negative when resistivity falls as temperature rises. This happens in semiconductors: heating breaks more covalent bonds and the number of charge carriers n rises steeply, which outweighs the shorter relaxation time.
Silicon is a semiconductor, so its \( \alpha \) is negative.
Silver, platinum and tungsten are metals: in them n is fixed and heating only increases collisions, so their resistivity rises and \( \alpha \) is positive.
NCERT (2026-27):
Temperature Dependence of Resistivity – “… Unlike metals, the resistivities of semiconductors decrease with increasing temperatures. A typical dependence is shown in Fig. 3.10.”
