Q1. A small region of an impure silicon crystal with dimensions 1.25 × 10-6 m × 10-3 m × 10-3 m has only the ions (with charge + 1.6 × 10-19 C) present with a volume density of 1025/m3. The rest of the crystal volume contains equal densities of electrons (with charge -1.6 × 10-19 C) and positive ions. The net total charge of the crystal is
- (a) 3 × 10-6 C
- (b) 1 × 10-6 C
- (c) 1.5 × 10-6 C
- (d) 2 × 10-6 C