JEE Physics Semiconductor Electronics MCQs Set A

Question. The semiconductors are generally
(a) Tetravalent
(b) Trivalent
(c) Divalent
(d) Monovalent

Answer: A

Question. The resistivity of a semiconductor depends upon
(a) The nature of atoms
(b) Size and types of motion
(c) Type of bonds
(d) Size of the atom

Answer: A

Question. The impurity atoms with which pure silicon should be doped to make a p-type semiconductor are those of
(a) Boron
(b) Copper
(c) Antimony
(d) Phosphorus

Answer: A

Question. A pure semiconductor has
(a) A finite resistance which decreases with temperature
(b) A finite resistance which increases with temperature
(c) A finite resistance which does not depend upon temperature
(d) An infinite resistance at 0°C

Answer: A

Question. The rate of recombination or generation are governed by the law(s) of
(a) Thermodynamics
(b) Chromodynamics
(c) Electrical neutrality
(d) Mass conservation

Answer: A

Question. An n-type semiconductor is electrically
(a) Neutral
(b) Negative
(c) May be positive or negative
(d) Positive

Answer: A

Question. A solid having uppermost energy band partially filled with electrons is called
(a) A conductor
(b) A semiconductor
(c) None of these
(d) An insulator

Answer: A

Question. The energy gap for an insulator may be
(a) 6 eV
(b) 0.7 eV
(c) 0.02 eV
(d) 1.1 eV

Answer: A

Question. In an intrinsic semiconductor, the density of conduction electrons is 7.07 × 10¹⁵ m^–3. When it is doped with indium, the density of holes becomes 5 × 10²² m^–3. Find the density of conduction electrons in doped semiconductor
(a) 1 × 10⁹ m^–3
(b) 7 × 10¹⁵ m^–3
(c) 5 × 10²² m^–3
(d) Zero

Answer: A

Question.  In an unbiased p-n junction which of the following is correct?
(a) n-side is at higher potential than p-side
(b) Both p-side and n-side are at the same potential
(c) p-side is at higher potential than n-side
(d) Any of the above is possible depending upon the carrier density in the two sides

Answer: A

Question. In a full wave rectifier circuit operating from 50 Hz mains frequency, the fundamental frequency in the ripple would be
(a) 100 Hz
(b) 70.7 Hz
(c) 25 Hz

Answer: A

Question. In a semiconductor diode, the reverse biased current is due to drift of free electrons and holes caused by
(a) Thermal excitations only
(b) Impurity atoms only
(c) Both
(d) None of these

Answer: A

Question. The value of form factor in case of half wave rectifier is
(a) 1.57
(b) 1.27
(c) 0.48
(d) 1.11

Answer: A

Question.  In a semiconductor diode, P-side is earthed and N-side is put at potential of –2 V, the diode shall
(a) Conduct
(b) Not conduct
(c) Conduct partially
(d) Break down

Answer: A

Question. The zener diode is used for
(a) Stabilization
(b) All of these
(c) Amplification
(d) Rectification

Answer: A

Question. A junction diode, in which one of the p or n-sections is made very thin, can be used to convert light energy into electrical energy, then the diode is called
(a) Solar cell
(b) Photo diode
(c) Zener diode
(d) Light emitting diode

Answer: A

Question. The material suitable for making a solar cell is
(a) GaAs
(b) CdSe
(c) Ge
(d) PbS

Answer: A

Question. In which of the configurations of a transistor, the power gain is highest?
(a) Common emitter
(b) Common collector
(c) Same in all the three
(d) Common base

Answer: A

Question. In a transistor the base is very lightly doped as compared to the emitter because by doing so
(a) Recombination is decreased in the base region
(b) Base current is high
(c) The flow across the base region is mainly because of holes
(d) The flow across the base region is mainly because of electrons

Answer: A

Question. In a common base transistor circuit, the current gain is 0.98. On changing emitter current by 5.00 mA, the change in collector current is
(a) 4.9 mA
(b) 5.1 mA
(c) 2.45 mA
(d) 0.196 mA

Answer: A

Question. For a transistor amplifier power gain and voltage gain are 7.5 and 2.5 respectively. The value of the current gain will be
(a) 3
(b) 0.99
(c) 0.66
(d) 0.33

Answer: A

Question. In a silicon transistor, a change of 7.89 mA is the emitter current produces a change of 7.8 mA in the collector current. What change in the base current is necessary to produce an equivalent change in the collector current?
(a) 0.09 mA
(b) Zero
(c) 0.9 mA
(d) 9 mA

Answer: A

Question. Copper has face centred cubic lattice with interatomic spacing 2.5 Å. The value of lattice constant will be about
(a) 3.5 Å
(b) 7.0 Å
(c) 1.5 Å
(d) 0.35 Å

Answer: A

Question. Liquid crystal display monitors are made of
(a) Liquid crystals
(b) Polycrystals
(c) Single crystals
(d) Monocrystals

Answer: A

Question. Which of the following cannot be obtained from an IC?
(a) Inductor
(b) Capacitor
(c) Diode
(d) Resistor

Answer: A

Question. Operational amplifier is a
(a) Linear IC
(b) OR gate
(c) AND gate
(d) Digital IC

Answer: A

Question. In a zener diode, break down occurs in reverse bias due to
(a) Internal field emission
(b) All of these
(c) High doping concentration
(d) Impact ionisation

Answer: A

Question. In an n-p-n transistor working in active mode, the depletion region
(a) At emitter-base junction is thinner than that at collector-base junction
(b) At the two junctions have equals width
(c) At emitter-base junction is wider than that at collector-base junction
(d) Is not formed

Answer: A

Question. A p-n photodiode is manufactured from a semiconductor with band gap of 3.1 eV. Which of the following wavelengths can be detected by it?
(a) Both
(b) 4000 Å
(c) 3900 Å
(d) NONE OF THESE

Answer: A

Question. The electrical conductivity of a semiconductor increases when electromagnetic radiation of wavelength shorter than 2480 nm is incident on it. The band gap of the semiconductor is
(a) 0.5 eV
(b) 0.7 eV
(c) 1.1 eV
(d) 0.3 eV

Answer: A

Question. Zener breakdown takes place if
(a) Doped impurity is high
(b) Less impurity in p-type
(c) Doped impurity is low
(d) Less impurity in N-part

Answer: A

Question. In a p-n junction solar cell, the value of photo-electromotive force produced by monochromatic light is proportional to the
(a) Intensity of light falling on the cell
(b) Voltage applied at the p-n junction
(c) Barrier voltage at the p-n junction
(d) Frequency of light falling on the cell

Answer: A

Question. In a transistor the collector current is always less than the emitter current because
(a) A few electrons are lost in the base and only remaining one’s reach the collector
(b) Collector being reverse biased, attracts less electrons
(c) Collector side is reverse biased and the emitter side is forward biased
(d) Collector side is forward biased and emitter side is reverse biased

Answer: A

Question. The depletion region of p-n junction has a thickness of the order of
(a) 10^–6 m
(b) 10^–3 m
(c) 10^–2 m
(d) 10^–12 m

Answer: A

Question. In an n-p-n transistor, the collector current is 10 mA. If 90% of the electrons emitted reach the collector, then the emitter current will be
(a) 11 mA
(b) 1 mA
(c) 0.1 mA
(d) 9 mA

Answer: A