Observation

This question was not popular among candidates. Most candidates failed to distinguish metals from semiconductors in terms of energy bands. The distinction should have been correctly given by making reference to the overlap between conduction band and valence band in metals; but the separation of the bands by forbidden gap in semiconductors. That increase in temperature in their electrical resistance was correctly given by many.

The expected answer is

  (a)     Distinction between metals and semiconductors

     In metals, the valence band and the conduction band overlap (no forbidden gap), while in semiconductors, the valence band and the conduction band are separated
by the forbidden gap.

 (b)       Effect of increasing temperature on the electrical resistance of a semiconductor                
Decrease in electrical resistance                                            

(c)        Effect of increasing temperature on the electrical resistance of a semiconductor                
Decrease in electrical resistance.