The temperature dependence of resistances of Cu and undoped Si in the temperature range 300-400 K, is best described by :
- (A)Linear increase for Cu, exponential increase for Si.
- (B)Linear increase for Cu, exponential decrease for Si.✓ Correct
- (C)Linear decrease for Cu, linear decrease for Si.
- (D)Linear increase for Cu, linear increase for Si.
Answer: (B)
Solution
Copper is a metal, where resistance comes from electrons scattering off lattice vibrations; as temperature rises the vibrations grow and the resistance climbs in an almost straight line, . Undoped silicon is an intrinsic semiconductor, where heating releases many more charge carriers across the gap, so its resistance falls, and falls exponentially. Copper thus shows a linear increase while silicon shows an exponential decrease.
JEE Main · 2016 · 03 Apr 2016 · Offline · Single correct option