Semiconductor Devices PYQs Set 7 (PDF)

Set 7 of 16 · Questions 181-210 of 467

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Mere Teacher · Previous Year Questions NEET Physics · Semiconductor Devices · Set 7 (Q181-210)
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181. $The energy gap of an LED is 2.4 eV . When the LED is switched 'ON', the momentum of the emitted photons is$ (1) $1.28 \times 10^{- 27} kg m s^{- 1}$ (2) $2.56 \times 10^{- 27} kg m s^{- 1}$ (3) $1.28 \times 10^{- 11} kg m s^{- 1}$ (4) $0.64 \times 10^{- 27} kg m s^{- 1}$ 182. $An amplifier has a voltage gain A_{v} = 1000 . The voltage gain in dB is [2006]$ (1) $20 dB$ (2) $60 dB$ (3) $3 dB$ (4) $30 dB$ 183. $In a transistor circuit, if emitter and collector connections are interchanged then$ (1) $emitter current will increase.$ (2) $base current decreases.$ (3) $collector current increases.$ (4) $no current flows in the circuit.$ 184. $A p - n junction diode can withstand upto 20 mA current under forward bias. The diode has a potential difference of 0.5 V across it, which is assumed to be independent of current. What is the maximum voltage of the battery used to forward bias the diode when a resistance of 125Ω is connected in series with it?$ (1) $3.0 V$ (2) $2.5 V$ (3) $3.2 V$ (4) $2.0 V$ 185. $When the transistor is used as an amplifier$ (1) $Emitter-base junction must be reverse biased, Collector-base junction must be forward biased.$ (2) $Emitter-base junction must be forward biased, Collector-base junction must be forward biased.$ (3) $Emitter-base junction must be reverse biased, Collector-base junction must be reverse biased.$ (4) $Emitter-base junction must be forward biased, Collector-base junction must be reverse biased.$ 186. $In a full wave rectifier in which input voltage is represented by V = V_{M} sin ωt, then peak inversion voltage ofnon‐conducting diode will be [2018]$ (1) $- V_{Λ I}$ (2) $V_{M} /2$ (3) $2 V_{M}$ (4) $0$ 187. $The current gain for a transistor working as a common‐ base amplifier is 0.96. If the emitter current is 7.2 mA, Ll1e base current will be [2001]$ (1) $0.42 mA$ (2) $0.49 mA$ (3) $0.35 mA$ (4) $0.29 mA$ 188. $Choose the only false statement from the following [2005]$ (1) $Substances with energy gap of the order of 10 eV are insulators$ (2) $The conductivity of a semiconductor increases with increase in temperature$ (3) $In conductors the valence and conduction bands may overlap$ (4) $The resistivity of a semiconductor increases with increase in temperature$ 189. $For sky wave propagation of 10 MHz signal, what should be the minimum electron density in ionosphere? [2005]$ (1) $\sim 1 0^{14} m^{- 3}$ (2) $\sim 1 0^{6} m^{- 3}$ (3) $\sim 1.2 \times 1 0^{12} m^{- 3}$ (4) $\sim 1 0^{22} m^{- 3}$ 190. $Out of the following, which one is a forward biased diode? [NEET 2020]$ (1) (2) (3) (4) 191. $For transistor, the current ratio ' β_{dc}' is defined the ratio of$ (1) $collector current to emitter current$ (2) $collector current to base current$ (3) $base current to collector current$ (4) $emitter current to collector current$ 192. $Copper has face centered cubic (fcc) lattice with interatomic spacing equal to 2.54 A. The value of the lattice constant for this lattice is [2005]$ (1) $1.27 A$ (2) $5.08 A$ (3) $2.54 A$ (4) $3.59 A$ 193. $For a transistor, α_{dc} and β_{dc} are the current ratios, then value of \frac{β _{dc} - α _{dc}}{α _{dc} \cdot β _{dc}} is$ (1) $1$ (2) $1.5$ (3) $2$ (4) $2.5$ 194. $The band gap in a semi-conductor is 0.6 eV . The maximum wavelength of electromagnetic radiation which can create a hole-electron pair in this semiconductor is equal to [Use hc = 1242 eV - nm]$ (1) $2450 nm$ (2) $1150 nm$ (3) $2070 nm$ (4) $1050 nm$ 195. $Which one of the following represents forward bias diode? [NEET 2017]$ (1) (2) (3) (4) 196. $An intrinsic semiconductor is converted into n-type extrinsic semiconductor by doping it with [NEET 2020]$ (1) $phosphorus$ (2) $aluminium$ (3) $silver$ (4) $germanium$ 197. $If a small amount of antimony is added to germanium crystal [2011]$ (1) $the antimony becomes an acceptor atom$ (2) $there will be more free electrons than holes in the semiconductor$ (3) $its resistance is increased$ (4) $it becomes a p‐type semiconductor$ 198. $When the temperature of a semiconductor increases then$ (1) $number of free electrons only increases$ (2) $number of holes only increases$ (3) $both number of free electrons and number of holes increase$ (4) $both number of free electrons and number of holes decrease$ 199. $In common base circuit of a transistor, current amplification factor is 0.95 . Calculate the emitter current if base current is 0.2 mA .$ (1) $2 mA$ (2) $4 mA$ (3) $6 mA$ (4) $8 mA$ 200. $If an emitter current is changed by 4 mA, the collector current changes by 3.5 mA . The value of β will be -$ (1) $7$ (2) $0.875$ (3) $0.5$ (4) $3.5$ 201. $For an LED to emit light in visible region of the electromagnetic spectrum, it can have energy band gap in the range of, (Plank's constant, h = 6.6 \times 10^{- 34} Js and speed of light, e = 3 \times 10^{8} ms^{- 1} in vacuum)$ (1) $0.1 eV to 0.4 eV$ (2) $0.9 eV to 1.6 eV$ (3) $1.7 eV to 3.1 eV$ (4) $0.5 eV to 0.8 eV$ 202. $If the ratio of electron and hole currents in a semiconductor is \frac{7}{4} and the ratio of drift velocities of electrons and holes is \frac{5}{4}, then ratio of concentrations of electrons and holes will be$ (1) $5 : 7$ (2) $7 : 5$ (3) $5 : 9$ (4) $9 : 5$ 203. $A reverse biased Zener diode when operated in the breakdown region works as$ (1) $an amplifier$ (2) $an oscillator$ (3) $a voltage regulator$ (4) $a rectifier$ 204. $The energy gap in case of which of the following is less than 3 eV ?$ (1) $Aluminium$ (2) $Iron$ (3) $Germanium$ (4) $Copper$ 205. $C and Si both have same lattice structure, having 4 bonding electrons in each. However, C is insulator whereas Si is intrinsic semiconductor. This is because [2012]$ (1) $The four bonding electrons in the case of C lie in the third orbit, whereas for Si they lie in the fourth orbit$ (2) $In case of C the valance band is not completely filled at absolute zero temperature$ (3) $In case of C the conduction band is partly filled even at absolute zero temperature$ (4) $The four bonding electrons in the case of C lie in the second orbit, whereas in the case of Si they lie in the third orbit$ 206. $For a transistor in CE mode to be used as an amplifier, it must be operated in :$ (1) $Both cut-off and Saturation$ (2) $Saturation region only$ (3) $Cut-off region only$ (4) $The active region only$ 207. $Consider an amplifier circuit in which a transistor is used in common-emitter mode. The load resistance 3 kΩ . When a signal of 30 mV is added to base emitter voltage, the base current is changed by 30 μA and the collector current is changed by 3 mA . The power gain in this circuit will be$ (1) $10000$ (2) $20000$ (3) $30000$ (4) $40000$ 208. $Minority carriers in a p -type semiconductor are$ (1) $free electrons$ (2) $holes$ (3) $neither holes nor free electrons$ (4) $both holes and free electrons.$ 209. $In a common emitter (CE) amplifier having a voltage gain G, the transistor used has transconductance 0.03 mho and current gain 25. If the above transistor is replaced with another one with transconductance 0.02 mho and cu1Tent gain 20, the voltage gain will be [2013]$ (1) $\frac{2}{3} G$ (2) $1.5 G$ (3) $\frac{1}{3} G$ (4) $\frac{5}{4} G$ 210. $The acceptor level of a p-type semiconductor is 6 eV . The maximum wavelength of light which can create a hole would be : Given hc = 1242 eVnm .$ (1) $414 nm$ (2) $103.5 nm$ (3) $207 nm$ (4) $407 nm$