Question

For a metallic conductor, the correct representation of variation of resistance R with temperature T is :

Assertion (A) : The resistance of an intrinsic semiconductor decreases with increase in its temperature. Reason (R) : The number of conduction electrons as well as hole increase in an intrinsic semiconductor with rise in its temperature.

Assertion (A) : The temperature coefficient of resistance is positive for metals and negative for semi-conductors. Reason (R) : The charge carriers in metals are negatively charged whereas in semiconductors they are positively charged.

Derive the relation between the current and the drift velocity of free electrons in a conductor. Briefly explain the variation of resistance of a conductor with rise in temperature.