Silicon is a semiconductor. If a small amount of As is added to it, then its electrical conductivity 

(1) Decreases

(2) Increases

(3) Remains unchanged

(4) Becomes zero

A piece of copper and the other of germanium are cooled from the room temperature to 80 K, then which of the following would be a correct statement

(1) Resistance of each increases

(2) Resistance of each decreases

(3) Resistance of copper increases while that of germanium decreases

(4) Resistance of copper decreases while that of germanium increases

To obtain a P-type Si semiconductor, we need to dope pure Si with 

(1) Aluminium

(2) Phosphorous

(3) Oxygen

(4) Germanium

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 ${\mathrm{EG}}_1,{\mathrm{EG}}_{2 }\mathrm{and} {\mathrm{EG}}_3$ 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