CBSE Class 12 Physics Semiconductor Electronics Materials Devices and Simple Circuits MCQs Set D

Question. Which of the following statements is not true?
(a) The resistance of intrinsic semiconductor decreases with increase of temperature.
(b) Doping pures Si with trivalent impurities gives p- type semiconductors.
(c) The majority charges in n- type semiconductors are holes.
(d) A p-n junction can act as semiconductor diode.

Answer: C

Question. The depletion region of the zener diode is
(a) Thick
(b) Normal
(c) Very thin
(d) Very thick

Answer: C

Question. What is the level of dopping in zener diode?
(a) Lightly dopped
(b) Heavily dopped
(c) Moderately dopped
(d) No dopping

Answer: B

Question. The impurity atoms with which pure Si should be doped to make a p- type semiconductor is
(a) Phosphorus
(b) Boron
(c) Arsenic
(d) Antimony

Answer: B

Question. Holes are majority charge carriers in
(a) Intrinsic semiconductors.
(b) Ionic Solids
(c) p- type semiconductors
(d) Metals

Answer: C

Question. The energy band gap is maximum in
(a) Metals
(b) Superconductors
(c) Insulators
(d) Semiconductors

Answer: C

Question. The number of majority carriers crossing the junction of diode depends primarily on the
(a) Concentration of doping impurities
(b) Magnitude of potential barriers
(c) Magnitude of the forward bias voltage
(d) Rate of thermal generation of electron –hole pairs

Answer: D

Question. Hole is
(a) Antiparticle of electron
(b) A vacancy created when an electron leaves covalent bond
(c) Absence of free electrons
(d) An artificially created particle.

Answer: B

Question. In the depletion region of a diode
(a) There are no mobile charges
(b) Equal number of holes and electrons exist, making the region neutral.
(c) Recombination of holes and electrons has taken place.
(d) Immobile charge ions exist.

Answer: D

Question. When a p-n junction diode is reverse biased then
(a) No Current flows
(b) The depletion reason is increased
(c) The depletion reason is reduced
(d) Height of potential barrier is reduced

Answer: B

Question. Diode is used as
(a) Oscillator
(b) Amplifier
(c) Rectifier
(d) Modulator

Answer: C

Question. At absolute zero, Si acts as
(a) Non- metal
(b) Metal
(c) Insulator
(d) None of these

Answer: C

Question. In the middle of depletion layer of reverse biased p- n junction, the
(a) Electric field is zero
(b) Potential is zero
(c) Potential is maximum
(d) Electric field is maximum

Answer: C

Question.Which one statement is incorrect?
(a) Diode is used as rectifier
(b) Diode is used as half wave rectifier
(c) Diode is used as Amplifier
(d) Diode is used as full wave rectifier

Answer: C

Question. Zener diode is mostly used as
(a) Half wave rectifier
(b) Full wave rectifier
(c) Voltage regulator
(d) LED

Answer: C

Question. Zener diode is designed to specially work in which region without getting damaged ?
(a) Active region
(b) Break down region
(c) Forward Biased
(d) Reverse biased

Answer: B

Question: C and Si both have same lattice structure; having 4 bonding electrons in each. However, C is insulator whereas Si is intrinsic semiconductor. This is because
(a) in case of C the valence band is not completely filled at absolute zero temperature
(b) in case of C the conduction band is partly filled even at absolute zero temperature
(c) the four bonding electrons in the case of C lie in the second orbit, whereas in the case of Si they lie in the third
(d) the four bonding electrons in the case of C lie in the third orbit, whereas for Si they lie in the fourth orbit.
Answer: c

Question: For amplification by a triode, the signal to be amplified is given to
(a) the cathode
(b) the grid
(c) the glass envelope
(d) the anode 
Answer: b

 Question: For a p-type semiconductor, which of the following statements is true?
(a) Electrons are the majority carriers and pentavalent atoms are the dopants.
(b) Electrons are the majority carriers and trivalent atoms are the dopants.
(c) Holes are the majority carriers and trivalent atoms are the dopants.
(d) Holes are the majority carriers and pentavalent atoms are the dopants.
Answer: c

Question: In semiconductors at a room temperature
(a) the valence band is partially empty and the conduction band is partially filled
(b) the valence band is completely filled and the conduction band is partially filled
(c) the valence band is completely filled
(d) the conduction band is completely empty.
Answer: a

 Question: The increase in the width of the depletion region in a p-n junction diode is due to
(a) forward bias only
(b) reverse bias only
(c) both forward bias and reverse bias
(d) increase in forward current 
Answer: b

Question: When a triode is used as an amplifier the phase difference between the input signal voltage and the output is
(a) 0
(b) p
(c) p/2
(d) p/4.
Answer: b

 Question:Depletion layer consists of
(a) mobile ions
(b) protons
(c) electrons
(d) immobile ions 
Answer: d

 Question:Reverse bias applied to a junction diode
(a) lowers the potential barrier
(b) raises the potential barrier
(c) increases the majority carrier current
(d) increases the minority carrier current
Answer: b

 Question: In a p-n junction diode, change in temperature due to heating
(a) affects only reverse resistance
(b) affects only forward resistance
(c) does not affect resistance of p-n junction
(d) affects the overall V - I characteristics of p-n junction.
Answer: d

Question:Pure Si at 500 K has equal number of electron (ne) and hole (nh) concentrations of 1.5 × 10¹⁶ m^–3. Doping by indium increases nh to 4.5 × 10²² m^–3. The doped semiconductor is of
(a) p-type having electron concentration ne = 5 × 10⁹ m^–3
(b) n-type with electron concentration ne = 5 × 10²² m^–3
(c) p-type with electron concentration ne = 2.5 × 10¹⁰ m^–3
(d) n-type with electron concentration ne = 2.5 × 10²³ m^–3
Answer: a

 Question:A p-n junction diode can be used as
(a) condenser
(b) regulator
(c) amplifier
(d) rectifier 
Answer: d

 Question: For an electronic valve, the plate current I and plate voltage V in the space charge limited region are related as
(a) I is proportional to V 3/2
(b) I is proportional to V 2/3
(c) I is proportional to V
(d) I is proportional to V 2 
Answer: a

Question:In a n-type semiconductor, which of the following statement is true?
(a) Holes are minority carriers and pentavalent atoms are dopants.
(b) Holes are majority carriers and trivalent atoms are dopants.
(c) Electrons are majority carriers and trivalent atoms are dopants.
(d) Electrons are minority carriers and pentavalent atoms are dopants.
Answer: a

 Question:The given graph represents V-I characteristic for a semiconductor device. Which of the following statement is correct?
(a) It is V-I characteristic for solar cell where, point A represents open circuit voltage and point B short circuit current.
(b) It is for a solar cell and points A and B represent open circuit voltage and current, respectively.
(c) It is for a photodiode and points A and B represent open circuit voltage and current, respectively.
(d) It is for a LED and points A and B represent open circuit voltage and short circuit current, respectively. 
Answer: a

 Question: The peak voltage in the output of a half wave diode rectifier fed with a sinusoidal signal without filter is 10 V. The d.c. component of the output voltage is
(a) 10 / 2 V
(b) 10/p V
(c) 10 V
(d) 20/p V
Answer: b

 Question: Which one of the following statement is false? 
(a) Pure Si doped with trivalent impurities gives a p-type semiconductor.
(b) Majority carriers in a n-type semiconductor are holes.
(c) Minority carriers in a p-type semiconductor are electrons.
(d) The resistance of intrinsic semiconductor decreases with increase of temperature. 
Answer: b

Question: In an unbiased p-n junction, holes diffuse from the p-region to n-region because of
(a) he attraction of free electrons of n-region
(b) the higher hole concentration in p-region than that in n-region
(c) the higher concentration of electrons in the n-region than that in the p-region
(d) the potential difference across the p-n junction.
Answer: b

Question: Choose the only false statement from the following.
(a) In conductors the valence and conduction bands overlap.
(b) Substances with energy gap of the order of 10 eV are insulators.
(c) The resistivity of a semiconductor increases with increase in temperature.
(d) The conductivity of a semiconductor increases with increase in temperature.
Answer: c

Question: When using a triode, as an amplifier, the electrons Dare emitted by
(a) grid and collected by cathode only
(b) cathode and collected by the anode only
(c) anode and collected by cathode only
(d) anode and collected by the grid and by cathode.
Answer: b

Question:When n type semiconductor is heated
(a) number of electrons increases while that of holes decreases
(b) number of holes increases while that of electrons decreases
(c) number of electrons and holes remain same
(d) number of electrons and holes increases equally.
Answer: d