Which gates are represented by this figure 

(1) NAND gate

(2) AND gate

(3) NOT gate

(4) OR gate

In a crystal, the atoms are located at the position of

(1) Maximum potential energy

(2) Minimum potential energy

(3) Zero potential energy

(4) Infinite potential energy

The distance between the body centered atom and a corner atom in sodium (a = 4.225 Å) is 

(1) 3.66 Å

(2) 3.17 Å

(3) 2.99 Å

(4) 2.54 Å

In good conductors of electricity, the type of bonding that exists is 

(1) Ionic

(2) Vander Waals

(3) Covalent

(4) Metallic

Bonding is a germanium crystal (semi-conductor) is

(1) Metallic

(2) Ionic

(3) Vander Waal's type

(4) Covalent

A P-type semiconductor can be obtained by adding

(1) Arsenic to pure silicon

(2) Gallium to pure silicon

(3) Antimony to pure germanium

(4) Phosphorous to pure germanium

The valence of an impurity added to germanium crystal in order to convert it into a P-type semiconductor is

(1) 6

(2) 5

(3) 4

(4) 3

The valency of the impurity atom that is to be added to germanium crystal so as to make it an N-type semiconductor, is
1. 6

2. 5

3. 4

4. 3

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