Free Temperature Coefficient of Resistivity MCQs with Answers

1. As the temperature of a metal conductor rises, its resistance

• A. increases, because the lattice ions vibrate more and impede the electrons
• B. decreases, because the electrons move faster
• C. stays constant
• D. falls to zero

Explanation: More vigorous lattice vibrations scatter the drifting electrons more often, shortening the mean free path and raising resistance, which is why a filament lamp's resistance is much higher when lit. Semiconductors behave in the opposite way, since heating releases many more charge carriers and resistance drops sharply. That contrast is the basis of the thermistor.

2. The temperature coefficient of resistivity for a semiconductor such as silicon is

• A. positive
• B. zero
• C. negative
• D. always exactly one

Explanation: Heating a semiconductor promotes far more electrons across the energy gap than it adds scattering, so the number of charge carriers rises steeply and resistivity falls, giving a negative coefficient. Metals have a positive coefficient because their carrier number is already fixed and only scattering changes. A thermistor exploits the negative case to measure temperature.

3. The unit of temperature coefficient of resistivity is

• A. 1/C
• B. 1/K
• C. 1/A
• D. 1/s

Explanation: The coefficient is the fractional change in resistivity per unit rise in temperature, so the resistivity units cancel and only reciprocal temperature remains, giving per kelvin. Because a kelvin and a degree Celsius are the same size, per degree Celsius is numerically identical, which is why the first option is such a close distractor. Reciprocal ampere and reciprocal second belong to quite different quantities.