Chemistry PYQ 86 of 346 · States of Matter

With reference to conductors, consider the following statements:

1. The valence band and the conduction band overlap each other.
2. The resistivity of a conductor decreases exponentially with temperature.
3. Conductors conduct electric current less than semiconductors and more than insulators.

Which of the above statements is/are correct?

Show answer and explanation

Correct answer: (d) Only the first statement

Explanation

Statement 1 is correct: in a conductor, the valence band and the conduction band overlap, so electrons move freely and carry current.
Statement 2 is wrong: a conductor's resistivity increases with temperature, roughly in proportion to it, because the vibrating atoms scatter the electrons more. It is a semiconductor whose resistivity falls, roughly exponentially, as the temperature rises.
Statement 3 is wrong: conductors conduct better than semiconductors, which in turn conduct better than insulators.

So only the first statement is correct.