Semiconductor Devices PYQs Set 4 (PDF)

Set 4 of 16 · Questions 91-120 of 467

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Mere Teacher · Previous Year Questions NEET Physics · Semiconductor Devices · Set 4 (Q91-120)
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91. $The resistivity of a semiconductor at room temperature is in between$ (1) $10^{6} to 10^{8} Ωcm$ (2) $10^{- 2} to 10^{- 5} Ωcm$ (3) $10^{10} to 10^{12} Ωcm$ (4) $10^{- 3} to 10^{8} Ωcm$ 92. $In the reverse biasing of a p - n junction diode$ (1) $the width of the depletion layer decreases.$ (2) $the width of the depletion layer increases.$ (3) $the number of minority charge carriers increase.$ (4) $the number of majority charge carriers increase.$ 93. $A transistor is operated in common emitter configuration at constant collector voltage V_{c} = 1.5 V such that a change in the base current from 100 μA to 150 μA produces a change in the collector current from 5 mA to 10 mA . The current gain (β) is [2006]$ (1) $67$ (2) $75$ (3) $100$ (4) $50$ 94. $For a CE transistor amplifier, the current amplification factor is 59 and the emitter current is 6.6 mA . Then the base current is$ (1) $0.11 mA$ (2) $1.1 mA$ (3) $11 μA$ (4) $0.11 A$ 95. $Thermionic emission from a heated filament varies with its temperature T as [2002]$ (1) $T^{- 1}$ (2) $T$ (3) $T^{2}$ (4) $T^{3/2}$ 96. $A transistor connected at common emitter mode contains load resistance of 5 kΩ and an input resistance of 1 kΩ. If the input peak voltage is 5 mV and the current gain is 50, find the voltage gain.$ (1) $250$ (2) $500$ (3) $125$ (4) $50$ 97. $Statement-I : To get a steady dc output from the pulsating voltage received from a full wave rectifier we can connect a capacitor across the output parallel to the load R_{L} Statement-II : To get a steady dc output from the pulsating voltage received from a full wave rectifier we can connect an inductor in series with R_{L} . In the light of the above statements, choose the most appropriate answer from the options given below:$ (1) $Statement I is true but Statement II is false$ (2) $Statement I is false but Statement II is true$ (3) $Both Statement I and Statement II are false$ (4) $Both Statement I and Statement II are true$ 98. $In which of the following statements, the obtained impure semiconductor is of p -type?$ (1) $Germanium is doped with bismuth$ (2) $Silicon is doped with antimony$ (3) $Germanium is doped with gallium$ (4) $Silicon is doped with phosphorus$ 99. $Which one of the following represents forward bias diode? [2017]$ (1) (2) (3) (4) 100. $For an intrinsic semiconductor (n_{h}) and n_{e} are the number of holes per unit volume and number of electrons per unit volume respectively)$ (1) $n_{h} < n_{e}$ (2) $n_{h} = n_{e}$ (3) $n_{h} = n_{e} 2$ (4) $n_{h} > n_{e}$ 101. $Pure Si at 500 K has equal number of electron (n_{e}) and hole (n_{h}) concentrations of 1.5 \times 1 0^{16} m^{- 3} . Doping by indium increases n_{h} to 4.5 \times 1 0^{22} m^{- 3} . The doped semiconductor is of [2011]$ (1) $n‐type with electron concentration n_{e} = 5 \times 1 0^{22} m^{- 3}$ (2) $p‐type with electron concentration n_{e} = 2.5 \times 1 0^{10} m^{- 3}$ (3) $n‐type with electron concentration n_{e} = 2.5 \times 1 0^{23} m^{- 3}$ (4) $p‐type having electron concentration n_{e} = 5 \times 1 0^{9} m^{- 3}$ 102. $If the ratio of the concentration of electrons to that of holes in a semiconductor is \frac{7}{5} and the ratio of currents is \frac{7}{4}, then what is the ratio of their drift velocities?$ (1) $5/8$ (2) $4/5$ (3) $5/4$ (4) $4/7$ 103. $When a p - n junction diode is in forward bias, which type of charge carriers flows in the connecting wire?$ (1) $Free electrons$ (2) $Ions$ (3) $Protons$ (4) $Holes$ 104. $A full wave rectifier circuit consists of two p - n junction diodes, a centre-tapped transformer, capacitor and a load resistance. Which of these components remove the AC ripple from the rectified output? [NEET 2023]$ (1) $p - n junction diodes$ (2) $Capacitor$ (3) $Load resistance$ (4) $A centre-tapped transformer$ 105. $In a transistor circuit, the collector current is changed by 8.9 mA, if the emitter current is changed to 9.0 mA . The value of current amplification factor β is$ (1) $89$ (2) $92$ (3) $84$ (4) $96$ 106. $Current I through a given p - n junction when a voltage V is applied across it is given to be I = I_{0} (e^{\frac{V}{2 V _{T}}} - 1) where I_{0} and V_{T} are constants. If r_{d} (I) is the dynamic resistance of the junction, then r_{d} (1000 I_{0}) = α r_{d} (10 I_{0}), where α is approximately equal to$ (1) $10$ (2) $1/10$ (3) $1/100$ (4) $1/1000$ 107. $Zener breakdown occurs in a p - n junction having p and n both:$ (1) $lightly doped and have wide depletion layer.$ (2) $heavily doped and have narrow depletion layer.$ (3) $heavily doped and have wide depletion layer.$ (4) $lightly doped and have narrow depletion layer.$ 108. $Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R Assertion A : Photodiodes are preferably operated in reverse bias condition for light intensity measurement. Reason R : The current in the forward bias is more than the current in the reverse bias for a p-n junction diode. In the light of the above statement, choose the correct answer from the options given below :$ (1) $A is false but R is true$ (2) $Both A and R are true but R is NOT the correct explanation of A$ (3) $A is true but R is false$ (4) $Both A and R are true and R is the correct explanation of A$ 109. $In a photodiode, the value of the emf produced by a monochromatic light beam is directly proportional to$ (1) $the barrier potential at p - n junction$ (2) $the intensity of light falling on the photodiode$ (3) $the frequency of light falling on the photodiode$ (4) $the voltage applied at the p - n junction$ 110. $In a transistor, in common emitter configuration, the ratio of power gain to voltage gain is$ (1) $α$ (2) $\frac{β}{α}$ (3) $βα$ (4) $β$ 111. $The input resistance of a common emitter transistor amplifier, if the output resistance is 500 kΩ, the current gain α = 0.98 and power gain is 6.0625 \times 1 0^{6}, is [2008]$ (1) $100 Ω$ (2) $300 Ω$ (3) $198 Ω$ (4) $400 Ω$ 112. $Which of the following statement is not correct in the case of light emitting diodes? (A) It is a heavily doped p-n junction. (B) It emits light only when it is forward biased. (C) It emits light only when it is reverse biased. (D) The energy of the light emitted is equal to or slightly less than the energy gap of the semiconductor used. Choose the correct answer from the options given below :$ (1) $C and D$ (2) $A$ (3) $C$ (4) $B$ 113. $The number of silicon atoms per m^{3} is 5 \times 10^{28} . This is doped with 4.5 \times 10^{21} atoms / m^{3} of Arsenic. The ratio of number of electrons to number of holes after doping is (Take n_{i} = Number of thermally-generated electrons (= 1.5 \times 10^{16} / m^{3})$ (1) $4.5 \times 10^{12}$ (2) $8 \times 10^{14}$ (3) $9 \times 10^{12}$ (4) $None$ 114. $In a transistor the collector current is always less than the emitter current because$ (1) $collector side is reverse biased and the emitter side is forward biased$ (2) $a few electrons are lost in the base and only remaining ones reach the collector$ (3) $collector being reverse biased, attracts less electrons$ (4) $collector side is forward biased and emitter side is reverse biased.$ 115. $A full-wave rectifier with diodes D_{1} and D_{2} is used to rectify 50 Hz alternating voltage. The diode D_{1} conducts times in one second.$ (1) $100$ (2) $25$ (3) $75$ (4) $50$ 116. $The electron concentration in an n -type semiconductor is the same as hole concentration in a p -type semiconductor. An external field (electric) is applied across each of them. Compare the currents in them. [NEET 2021]$ (1) $Current in n -type = Current in p -type$ (2) $Current in p -type > Current in n -type$ (3) $Current in n -type > Current in p -type$ (4) $No current will flow in p -type, current will only flow in n -type$ 117. $The following truth table with A and B as inputs is for gate. A 1100 B 0110 Output 1010$ (1) $AND$ (2) $OR$ (3) $XOR$ (4) $NOR$ 118. $When the conductivity of a semiconductor is only due to the breaking of the covalent bonds, the semiconductor is called$ (1) $donor$ (2) $intrinsic$ (3) $acceptor$ (4) $extrinsic$ 119. $In a common base amplifier, the phase difference between the input signal voltage and output voltage is :$ (1) $\frac{π}{4}$ (2) $π$ (3) $zero$ (4) $\frac{π}{2}$ 120. $A light emitting diode (LED) is fabricated using GaAs semiconducting material whose band gap is 1.42 eV . The wavelength of light emitted from the LED is :$ (1) $1400 nm$ (2) $650 nm$ (3) $875 nm$ (4) $1243 nm$