The forbidden energy bandgap in conductors, semiconductors, and insulators are ${\mathrm{EG}}_1,{\mathrm{EG}}_{2 }\mathrm{and} {\mathrm{EG}}_3$ and respectively. The relation among them is

(1) ${\mathrm{EG}}_1={\mathrm{EG}}_{2 }={\mathrm{EG}}_3$

(2) ${\mathrm{EG}}_1<{\mathrm{EG}}_{2 }<{\mathrm{EG}}_3$

(3) ${\mathrm{EG}}_1>{\mathrm{EG}}_{2 }>{\mathrm{EG}}_3$ 

(4) ${\mathrm{EG}}_1<{\mathrm{EG}}_{2 }>{\mathrm{EG}}_3$

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) ${10}^{-7}$

How much is the forbidden gap (approximately) in the energy bands of germanium at room temperature? 
1. $1.1~\text{eV}$
2. $0.1~\text{eV}$
3. $0.67~\text{eV}$
4. $6.7~\text{eV}$

In P-type semiconductor, the majority and minority charge carriers are respectively

(1) Protons and electrons

(2) Electrons and protons

(3) Electrons and holes

(4) Holes and electrons

At zero Kelvin a piece of germanium

(1) Becomes semiconductor

(2) Becomes good conductor

(3) Becomes bad conductor

(4) Has maximum conductivity

A semiconductor is cooled from ${\mathrm{T}}_1\mathrm{K}$ to ${\mathrm{T}}_2\mathrm{K}$. Its resistance

(1) Will decrease

(3) Will increase

(3) Will first decrease and then increase

(4) Will not change