
Question 1:
Which among the following is the most commonly used semiconductor?
(a) Silicon
(b) Carbon
(c) Germanium
(d) Sulphur
Question 2:
Which of the following is compound semiconductor?
(a)CdS
(b)CdAs
(c)InP
(d)All of these
Question 3:
Which of the following is created when trivalent impurities are added to a semiconductor?
(a) Free electrons
(b) Holes
(c) Bound electrons
(d) Valence electrons
Question 4:
The relation between the number of free electrons in semiconductor and its temperature is given as
(a) nαT
(b) nαT2
(c) nαT3/2
(d) nα
Question 5:
Which of the following diode is used in voltage regulator?
(a) Photo diode
(b) Zener diode
(c) LED
(d) p-n junction diode
Question 6:
Which material has a negative temperature coefficient?
(a) Carbon
(b) Aluminium
(c) Brass
(d) Copper
Question 7:
A semiconductor placed at 0k, it will behave as
(a) conductor
(b) insulator
(c) metal
(d) semiconductor
Question 8:
The forbidden energy gap for germanium is
(a) 0.12 eV
(b) 0.72 eV
(c) 1.11 eV
(d) 1.52 eV
Question 9:
In a middle of depletion layer of a reverse biased p-n junction, the
(a) electric field is zero
(b) potential is maximum
(c) electric field is maximum
(d) potential is 0
Question 10:
The output of OR gate is 1 when
(a) if both the inputs are 0
(b) if either or both inputs are 1
(c) only if both inputs are 1
(d) if either input 0
Question 11:
Why should a photodiode be operated at a reverse bias?
Question 12:
Draw the voltage-current characteristic for a Zener diode.
Question 13:
Suppose a pure Si crystal has 5 × 1028 atoms m–3. It is doped by 1 ppm concentration of pentavalent As. Calculate the number of electrons and holes. Given that ni =1.5 × 1016 m–3.
Question 14:
Explain briefly, which property of the characteristic enables us to use Zener diode as voltage regulator.
Question 15:
Draw the energy band diagram of n-type and p-type semiconductors.
Question 16:
A Zener of power rating 1 W is to be used as a voltage regulator. If Zener has a breakdown of 5 V and it has to regulate voltage which fluctuated between 3 V and 7 V, what should be the value of R, for safe operation (figure)?
Question 17:
Define the terms ‘potential barrier’ and ‘depletion region’ for a p – n junction diode. State how the thickness of the depletion region will change when the p-n junction diode is (i) forward biased and (ii) reverse biased.
Question 18:
With the help of a diagram, show the biasing of a light-emitting diode (LED). Give its two advantages over conventional incandescent lamps.
Question 19:
Draw the circuit diagram of a full-wave rectifier and explain its working. Also, give the input and output waveforms.
Question 20:
Distinguish between conductors, insulators, and semiconductors on the basis of the band theory of solids.
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