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NCERT Solutions for class 12 Physics | Chapter 14 - Semiconductor Electronics

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Free download in PDF Class 12 Physics Chapter 14 Semiconductor Electronics Multiple Choice Questions and Answers for Board, JEE, NEET, AIIMS, JIPMER, IIT-JEE, AIEE and other competitive exams. MCQ Questions for Class 12 Physics with Answers were prepared based on the latest exam pattern. These short solved questions or quizzes are provided by Gkseries. These will help the students for preparation of their examination./p>

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(1) n forward biasing of the p–n junction
[A] the positive terminal of the battery is connected to

p–side and the depletion region becomes thick

[B] the positive terminal of the battery is connected to

n–side and the depletion region becomes thin

[C] the positive terminal of the battery is connected to

n–side and the depletion region becomes thick

[D] the positive terminal of the battery is connected to

p–side and the depletion region becomes thin

Answer: the positive terminal of the battery is connected to

p–side and the depletion region becomes thin

(2) In the middle of the depletion layer of a reverse- biased p-n junction, the
[A] electric field is zero
[B] potential is maximum
[C] electric field is maximum
[D] potential is zero
Answer: electric field is maximum

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(3) When p-n junction diode is forward biased then
[A] both the depletion region and barrier height are reduced
[B] the depletion region is widened and barrier height is reduced
[C] the depletion region is reduced and barrier height is increased
[D] Both the depletion region and barrier height are increased
Answer: both the depletion region and barrier height are reduced
(4) Barrier potential of a P-N junction diode does not depend on
[A] doping density
[B] diode design
[C] temperature
[D] forward bias
Answer: diode design
(5) In a half wave rectifier, the r.m.s. value of the a.c. component of the wave is
[A] equal to d.c. value
[B] more than d.c. value
[C] less than d.c. value
[D] zero
Answer: more than d.c. value
(6) The average value of output direct current in a full wave rectifier is
[A] I0/π
[B] I0/2
[C] π I0/2
[D] 2 I0/π
Answer: 2 I0/π
(7) The average value of output direct current in a half wave rectifier is
[A] I0/π
[B] I0/2
[C] π I0/2
[D] 2 I0/π
Answer: I0/π
(8) Bridge type rectifier uses
[A] four diodes
[B] six diodes
[C] two diodes
[D] one diode
Answer: four diodes
(9) The ratio of forward biased to reverse biased resistance for p-n junction diode is
[A] 10–1 : 1
[B] 10–2 : 1
[C] 104 : 1
[D] 10–4 : 1
Answer: 10–4 : 1
(10) In a P -N junction
[A] the potential of P & N sides becomes higher alternately
[B] the P side is at higher electrical potential than N side.
[C] the N side is at higher electric potential than P side.
[D] both P & N sides are at same potential.
Answer: the P side is at higher electrical potential than N side.
(11) For a junction diode the ratio of forward current (If) and reverse current (Ir) is

[e = electronic charge,

V = voltage applied across junction,

k = Boltzmann constant,

T = temperature in kelvin]

[A] e–V/kT
[B] eV/kT
[C] (e–eV/kT + 1) 
[D] (eeV/kT – 1)
Answer: (eeV/kT – 1)
(12) By increasing the temperature, the specific resistance of a conductor and a semiconductor
[A] increases for both
[B] decreases for both
[C] increases, decreases
[D] decreases, increases
Answer: increases, decreases
(13) An electric field is applied to a semiconductor. Let the number of charge carriers be n and the average drift speed be v. If the temperature is increased
[A] both n and v will increase
[B] n will increase but v will decrease
[C] v will increase but n will decrease
[D] both n and v will decrease
Answer: both n and v will increase
(14) When an impurity is doped into an intrinsic semiconductor, the conductivity of the semiconductor
[A] increases
[B] decreases
[C] remains the same
[D] becomes zero
Answer: increases
(15) One serious drawback of semi-conductor devices is
[A] they do not last for long time.
[B] they are costly
[C] they cannot be used with high voltage.
[D] they pollute the environment.
Answer: they are costly
(16) In semiconductors, at room temperature
[A] the conduction band is completely empty
[B] the valence band is partially empty and the conduction band is partially filled
[C] the valence band is completely filled and the conduction band is partially filled
[D] the valence band is completely filled
Answer: the valence band is completely filled and the conduction band is partially filled
(17) The relation between number of free electrons (n) in a semiconductor and temperature (T) is given by
[A] n α T
[B] n α T2
[C] n α √T
[D] n α T3/2
Answer: n α T3/2
(18) The mobility of free electrons is greater than that of free holes because
[A] they are light
[B] they carry negative charge
[C] they mutually collide less
[D] they require low energy to continue their motion
Answer: they are light
(19) In an n-type semiconductor, donor valence band is
[A] above the conduction band of the host crystal
[B] close to the valence band of the host crystal
[C] close to the conduction band of the host crystal
[D] below the valence band of the host crystal
Answer: close to the conduction band of the host crystal
(20) In a p-type semiconductor, the acceptor valence band is
[A] close to the valence band of the host crystal
[B] close to conduction band of the host crystal
[C] below the conduction band of the host crystal
[D] above the conduction band of the host crystal
Answer: close to the valence band of the host crystal

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