A piece of silver and another of silicon are cooled from \( 15^\circ\mathrm{C} \) to \( 3^\circ\mathrm{C} \). What will be the effect on resistance of each?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Silver: decreases; Silicon: increases
Silver is a metal: when it is cooled, the thermal vibrations of the lattice fall, electrons collide less often, and the resistivity decreases. Silicon is a semiconductor: cooling frees fewer charge carriers (electrons and holes), so its resistivity increases.
Option (2) Silver: decreases; Silicon: increases — Correct. Silver (metal) decreases; silicon (semiconductor) increases.
NCERT (2026-27):
Temperature Dependence of Resistivity – “… Unlike metals, the resistivities of semiconductors decrease with increasing temperatures.”
Temperature Dependence of Resistivity – “… In a metal, \( n \) is not dependent on temperature to any appreciable extent and thus the decrease in the value of \( \tau \) with rise in temperature causes \( \rho \) to increase as we have observed.”