The electrical conductivity of a semiconductor

(1) Decreases with the rise in its temperature

(2) Increases with the rise in its temperature

(3) Does not change with the rise in its temperature

(4) First increases and then decreases with the rise in its temperature

When a semiconductor is heated, its resistance

(1) Decreases

(2) Increases

(3) Remains unchanged

(4) Nothing is definite

In an insulator, the forbidden energy gap between the valence band and conduction band is of the order of

(1) 1  MeV

(2)  0.1 MeV

(3) 1 eV 

(4) 15 eV

An N-type semiconductor is

(1) Negatively charged

(2) Positively charged

(3) Neutral

(4) None of these

The energy band gap of Si is

(1) 0.70 eV

(2) 1.1 eV

(3) Between 0.70 eV to 1.1 eV

(4) 5 eV

The forbidden energy bandgap in conductors, semiconductors, and insulators are ${\mathrm{EG}}_1,{\mathrm{EG}}_{2<mspace\; width="1em"></mspace>}\mathrm{and}<mspace\; width="1em"></mspace>{\mathrm{EG}}_3$ and respectively. The relation among them is

(1) ${\mathrm{EG}}_1={\mathrm{EG}}_{2<mspace\; width="1em"></mspace>}={\mathrm{EG}}_3$

(2) ${\mathrm{EG}}_1<{\mathrm{EG}}_{2<mspace\; width="1em"></mspace>}<{\mathrm{EG}}_3$

(3) ${\mathrm{EG}}_1>{\mathrm{EG}}_{2<mspace\; width="1em"></mspace>}>{\mathrm{EG}}_3$ 

(4) ${\mathrm{EG}}_1<{\mathrm{EG}}_{2<mspace\; width="1em"></mspace>}>{\mathrm{EG}}_3$

When Ge crystals are doped with phosphorus atom, then it becomes 

(1) Insulator

(2) P-type

(3) N-type

(4) Superconductor

Let ${\mathrm{n}}_{\mathrm{P}}$ and ${\mathrm{n}}_{\mathrm{e}}$ be the number of holes and conduction electrons respectively in a semiconductor. Then

(1) ${\mathrm{n}}_{\mathrm{P}}$>${\mathrm{n}}_{\mathrm{e}}$ in an intrinsic semiconductor

(2) ${\mathrm{n}}_{\mathrm{P}}$=${\mathrm{n}}_{\mathrm{e}}$ in an extrinsic semiconductor

(3) ${\mathrm{n}}_{\mathrm{P}}$=${\mathrm{n}}_{\mathrm{e}}$ in an intrinsic semiconductor

(4) ${\mathrm{n}}_{\mathrm{e}}$<${\mathrm{n}}_{\mathrm{P}}$ in an intrinsic semiconductor

Wires P and Q have the same resistance at ordinary (room) temperature. When heated, resistance of P increases and that of Q decreases. We conclude that

1. P and Q are conductors of different materials

2. P is N-type semiconductor and Q is P-type semiconductor

3. P is semiconductor and Q is conductor

4. P is conductor and Q is semiconductor

In extrinsic P and N-type, semiconductor materials, the ratio of the impurity atoms to the pure semiconductor atoms is about 
(1) 1                   

(2) ${10}^{-1}$

(3) ${10}^{-4}$             

(4) ${10}^{-7}$