Physics - Solids and Semiconductor Devices
Exam Duration: 45 Mins Total Questions : 30
The electron distribution of an atom of silicon is
- (a)
2,10,2
- (b)
2,8,4
- (c)
2,7,5
- (d)
2,4,8
Sodium chloride solution in water is by nature
- (a)
conductor
- (b)
insulator
- (c)
semi conductor
- (d)
metal
Ice has
- (a)
ionic binding
- (b)
covalent binding
- (c)
metallic bonding
- (d)
van der Waals' binding
A bcc crystal has a lattice parameter of \(3.4\mathring { A } \).Its atomic radius is
- (a)
\(3.10\mathring { A } \)
- (b)
\(1.47\mathring { A } \)
- (c)
\(2.60\mathring { A } \)
- (d)
None of the above
The number of molecules per unit cell in fcc lattice is
- (a)
1
- (b)
2
- (c)
4
- (d)
8
Space lattice is
- (a)
purely a geometrical concept
- (b)
in actual existent
- (c)
purely a physical concept
- (d)
arrays of atoms placed in a periodical and ordered arrangement
The structure of NaCl is
- (a)
superposition of two fcc lattices
- (b)
having coordination number for same kind of ions is 12
- (c)
having coordination number for opposite kinds of ions is 6
- (d)
all of the above
The distance between the bod-centred atom and a corner atom in sodium(a=4.225 \(\mathring {A}\))is
- (a)
\(3.66\mathring {A}\)
- (b)
\(3.17\mathring {A}\)
- (c)
\(2.99\mathring {A}\)
- (d)
\(2.54\mathring {A}\)
Which of the following solids make the best mirrors?
- (a)
ionic solids
- (b)
covalent solids
- (c)
metallic solids
- (d)
dielectric solids
The forbidden band in germanium at 0 K is
- (a)
0.785 eV
- (b)
1.21 eV
- (c)
1.00 eV
- (d)
0.01 eV
Choose INCORRECT Statement
- (a)
mobility of a charge carrier equals its average speed(V) divided by the applied electric field(E)
- (b)
Donor type semiconductor is formed by adding impurity of valency 5
- (c)
Accepter type semiconductor is formed by adding impurity of valency 3
- (d)
Each donor atom contributes two free electrons
When we apply reverse bias to a junction diode it
- (a)
lowers the potential barrier
- (b)
raises the potential barrier
- (c)
Increases the majority carrier current
- (d)
Increases the minority carrier current
In a pn-junction with open ends
- (a)
holes and conduction electrons systematically go from the p-side to the n-side and from n-side to the p-side respectively
- (b)
there is no net charge transfer between the two sides
- (c)
there is a constant electric field near the junction
- (d)
All of the above
The value of \(\beta\)
- (a)
is always less than 1
- (b)
lies between 50 and 150
- (c)
is always greater than 150
- (d)
is always 100
In a transistor (\(\beta=45\)), the voltage across \(5 K\Omega\) load resistance in collector circuit is 5V. the base current is
- (a)
0.022 mA
- (b)
0.978 mA
- (c)
1.0 mA
- (d)
2.5 mA
The electrical conductivity of a semi conductor increases when electromagnetic radiation of wavelength shorter than 2480 nm is incident on it.The band gap (in eV) for semiconductor is
- (a)
0.9
- (b)
0.7
- (c)
0.5
- (d)
1.1
The part of a transistor which is heavily doped to produce a large number of majority carriers is
- (a)
base
- (b)
emitter
- (c)
collector
- (d)
none of these
N-type germanium is obtained on doping intrinsic germanium by
- (a)
aluminium
- (b)
boron
- (c)
phosphorus
- (d)
gold
Zener diode is used for
- (a)
rectification
- (b)
stabilisation
- (c)
amplification
- (d)
oscillation
A transistor is essentially
- (a)
a current operated device
- (b)
a power driven device
- (c)
a voltage operated device
- (d)
a resistance operated device
In a full wave rectifier with input frequency 50Hz, the ripple in the output is mainly of the frequency(in Hz)
- (a)
25
- (b)
50
- (c)
100
- (d)
None of these
In common-emitter circuit, the voltage gain is
- (a)
lowest
- (b)
highest
- (c)
zero
- (d)
Same as in common-base circuit
In Boolean Algebra A+A is equal to
- (a)
0
- (b)
1
- (c)
A
- (d)
2A
The following truth table corresponds to the logic gate
A | B | x |
0 | 0 | 0 |
0 | 1 | 1 |
1 | 0 | 1 |
1 | 1 | 1 |
- (a)
NAND
- (b)
OR
- (c)
AND
- (d)
XOR
The band gap inGe and Si ineV respectively is
- (a)
0.7,1.1
- (b)
1.1,0.7
- (c)
1.1,0
- (d)
0,1.1
In p-type semiconductor
- (a)
major current carrier is electrons
- (b)
major current carrier is mobile negative ions
- (c)
major current carrier is mobile holes
- (d)
the number of mobile holes exceeds the number of accepter
Holes are majority charge carriers in
- (a)
intrinsic semiconductor
- (b)
ionic solids
- (c)
p-type semiconductor
- (d)
metals