CBSE Class 12 Physics Electronic Devices Assignment Set B

Important Questions for NCERT Class 12 Physics Electronic Devices

Question. Which one of the following is true about the p-type and n-type semi-conductor ? 
(a) n-type semi-conductor have holes in majority.
(b) the concentration of electrons and holes are equal in both n-type and p -type semiconductors.
(c) n-type semi-conductors have free electrons in majority.
(d) p-type semi-conductor has excess negative charge.

Answer   C

Question. When n-p-n transistor is used as an amplifier, then 
(a) electrons move from base to collector
(b) holes move from emitter to base
(c) electrons move from collector to base
(d) holes move from base to emitter

Answer   A

Question. When added an impurity into the silicon which one of the following produces n-type of semiconductors : 
(a) iron
(b) magnesium
(c) aluminium
(d) phosphorous

Answer   D

Question. When the two semiconductors p- and n-type are brought into contact they form a p-n junction, which acts like a/an : 
(a) rectifier
(b) amplifier
(c) conductor
(d) oscillator

Answer   A

Question. The transfer ratio b of a transistor is 50. The input resistance of the transistor when used in the common emitter configuration is 1kW. The peak value of the collector A.C. current for an A.C. input voltage of 0.01 V, is 
(a) 500 μA
(b) 0.25 μA
(c) 0.01 μA
(d) 100 μA

Answer   A

Question. Boolean algebra is essentially based on:
(a) Numbers
(b) Symbol
(c) Logic
(d) Truth

Answer   C

Question. An amplifier has a voltage gain Av = 1000. The voltage gain in dB is: 
(a) 30 dB
(b) 60 dB
(c) 3 dB
(d) 20 dB

Answer   A

Question. A triode valve has an amplification factor of 20 and its plate is given a potential of 300 V. The grid voltage to reduce the plate current to zero, is 
(a) 25 V
(b) 15 V
(c) 12 V
(d) 10 V

Answer   B

Question. If collector current is 120 mA and base current is 2 mA and resistance gain is 3, what is power gain?
(a) 180
(b) 10800 
(c) 1.8
(d) 18

Answer   B

Question. Diode is used as a/an 
(a) modulator
(b) rectifier
(c) oscillator
(d) amplifier

Answer   B

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

Answer   B

Question. In n-type semiconductor, majority charge carriers are 
(a) electrons
(b) neutrons
(c) holes
(d) protons

Answer   A

Question. The input resistance of a common emitter transistor amplifier, if the output resistance is 500 kW, the current gain a = 0.98 and power gain is 6.0625 × 10⁶, is 
(a) 198 W
(b) 300 W
(c) 100 W
(d) 400 W

Answer   A

Question. If the highest modulating frequency of the wave is 5 kHz, the number of stations that can be accomdated in a 150 kHz bandwidth are
(a) 15
(b) 10
(c) 5
(d) none of these

Answer   A

Question. Zener diode acts as a/an 
(a) oscillator
(b) regulator
(c) rectifier
(d) filter

Answer   B

Question. Mobilities of electrons and holes in a sample of intrinsic Ge at room temperature are 0.35m²/V–s and 0.18m²/V–s respectively. If the electron and hole densities are each equal to 2.5×10¹⁹/m3, the Ge conductivity will be
(a) 3.12 S/m
(b) 2.12 S/m
(c) 1.12 S/m
(d) 4.12 S/m

Answer   B

Question. In a full wave rectifier circuit operating from 50 Hz mains frequency, what is the fundamental frequency in the ripple? 
(a) 50 Hz
(b) 100 Hz
(c) 70 Hz
(d) 25 Hz

Answer   B

Question. At 0 K temperature, a p-type semiconductor 
(a) has equal number of holes and free electrons
(b) has few holes but no free electrons
(c) has few holes and few free electrons
(d) does not have any charge carriers

Answer   D

Question. In p-type semiconductor major current carriers are :
(a) negative ions
(b) holes
(c) electrons
(d) all of these

Answer   B

Question. The cause of the potential barrier in a p-n junction diode is 
(a) depletion of positive charges near the junction
(b) concentration of positive charges near the junction
(c) depletion of negative charges near the junction
(d) concentration of positive and negative charges near the junction

Answer   D

Please refer to attached file for CBSE Class 12 Physics Electronic Devices Assignment Set B