A common emitter amplifier is designed with NPN transistor ($\mathrm{\alpha }$ = 0.99). The input impedance is 1 K$\mathrm{\Omega }$ and load is 10 K$\mathrm{\Omega }$. The voltage gain will be 

(1) 9.9                           

(2) 99
(3) 990                         

(4) 9900

For the given combination of gates, if the logic states of inputs A, B, C are as follows A = B = C = 0 and A = B = 1, C = 0 then the logic states of output D are

(a) 0, 0
(b) 0, 1
(c) 1, 0
(d) 1, 1

Bonding in a germanium crystal (semi- conductor) is

(1) Metallic                         

(2) Ionic
(3) Vander Waal's type         

(4) Covalent

In a semiconductor, the concentration of electrons is $8\times {10}^{14} {\mathrm{cm}}^3$ and that of the holes is $5\times {10}^{12} {\mathrm{cm}}^3$. The semiconductor is

(1) P-type                   

(2) N-type
(3) Intrinsic                 

(4) PNP-type

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

A N-type semiconductor is

(1) Negatively charged       

(2) Positively charged
(3) Neutral                         

(4) None of these

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 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

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

(1) 100 eV                     

(2) 10 eV
(3) 1 eV                         

(4) 0 eV