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

In intrinsic semiconductor at room temperature, the number of electrons and holes are

(1) Equal

(2) Zero

(3) Unequal

(4) Infinite

In a semiconductor, the separation between the conduction band and valence band is of the order of

(1) 100 eV

(2) 10 eV

(3) 1 eV

(4) 0 eV