33. Choose the only false statement from the following

33. Choose the only false statement from the following.

(a) In conductors, the valence and conduction bands may overlap.

(b) Substances with energy gap of the order of 10eV are insulators.

(c) The resistivity of a semiconductor increases with increase in temperature.

(d) The conductivity of a semiconductor increases with increase in temperature.

Answer :  (c) The resistivity of a semiconductor increases with increase in temperature.

\( \text{As } T \uparrow\ \rho \downarrow \)

\( \rho = \frac{m}{(n e^{2} \tau)} \)

\( \text{As } T \uparrow\ n\ \text{free}\ e^- \uparrow\ \rho \downarrow \)