Question

The temperature coefficient of a metal is ___ and that of a semiconductor is ___ respectively

• A. \(+ve, -ve\)
• B. \(+ve, +ve\)
• C. \(-ve, +ve\)
• D. \(-ve, -ve\)

Hint:

Metals: +ve coefficient, Semiconductors: –ve coefficient.

Answer 1

The Correct Option is A

Step 1: Examine carrier density in metals.
Metals have a fixed, very large number of free electrons (one or two per atom). As temperature rises, these electrons collide more frequently with vibrating lattice ions, increasing resistance. So resistance goes UP with temperature, meaning the temperature coefficient is positive.

Step 2: Examine carrier density in semiconductors.
In semiconductors, the number of free carriers is NOT fixed. At higher temperatures, more electron-hole pairs are thermally generated (intrinsic excitation across the bandgap). This sharp rise in carrier count dominates over any mobility decrease.

Step 3: Conclude the signs of each coefficient.
Metal resistance increases with temperature $\Rightarrow$ positive coefficient. Semiconductor resistance decreases with temperature because more carriers are created $\Rightarrow$ negative coefficient. \[ \boxed{+ve,\,-ve} \]