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

(1) In semi conductor which are responsible for conduction:
[A] only electron
[B] electron and hole both
[C] only hole
[D] None of these
Answer: electron and hole both
(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 zero.
Answer: potential zero.

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(3) p-n junction diode can be used as:
[A] amplifier
[B] oscillator
[C] detector
[D] modulator
Answer: detector
(4) For germanium crystal, the forbidden energy gap in joules
[A] 1.216 × 10-19
[B] 1.76 × 10-19
[C] 1.6 × 10-19
[D] zero
Answer: 1.216 × 10-19
(5) In reverse biasing:
[A] large amount of current flows
[B] no current flows
[C] potential barrier across junction increases
[D] depletion layer resistance increases
Answer: potential barrier across junction increases
(6) With fall of temperature, the forbidden energy gap of a semiconductor
[A] increases
[B] decreases
[C] sometimes increases and sometimes decreases
[D] remains unchanged
Answer: remains unchanged
(7) Main function of a transistor is to :
[A] rectify
[B] simplify
[C] amplify
[D] all the above
Answer: amplify
(8) In a common base amplifier the phase difference between the input signal voltage and output voltage is :
[A] π/2
[B] 0
[C] π/4
[D] π
Answer: 0
(9) On heating, resistance of semiconductors:
[A] decreases
[B] increases
[C] remains same
[D] first increases then decreases
Answer: decreases
(10) On applying reverse bias to a junction diode, it:
[A] lowers the potential barrier
[B] raise the potential barrier
[C] increases the majority carrier current
[D] increases the minority carrier current
Answer: raise the potential barrier
(11) In a p-type semiconductor, current conduction is by:
[A] atoms
[B] holes
[C] electrons
[D] protons
Answer: holes
(12) Energy bands in solids are a consequence of:
[A] Ohm’s Law
[B] Pauli’s exclusion principle
[C] Bohr’s theory
[D] Heisenberg’s uncertainty principle
Answer: Pauli’s exclusion principle
(13) To obtain p-type silicon semiconductor, we need to dope pure silicon with:
[A] aluminium
[B] phosphorus
[C] oxygen
[D] germanium
Answer: aluminium
(14) The relation between number of free electrons (n) in a semiconductor and temperature (T) is given by:
[A] n ∝ T
[B] n ∝ T²
[C] n ∝ T1/2
[D] n ∝ T3/2
Answer: n ∝ T3/2
(15) Number of electrons in the valence shell of a semiconductor is:
[A] 1
[B] 2
[C] 3
[D] 4
Answer: 4
(16) The material most commonly used to manufacture electronic solid state devices is :
[A] copper
[B] silicon
[C] germanium
[D] aluminium
Answer: silicon
(17) Crystal diode is:
[A] amplifying device
[B] fluctuating device
[C] non-linear device
[D] linear device
Answer: non-linear device
(18) Winch of the following gate is not an universal gate?
[A] OR
[B] NOT
[C] AND
[D] NAND
Answer: NAND
(19) In intrinsic semiconductor at room temperature, the number of electrons and holes are:
[A] equal
[B] unequal
[C] infinite
[D] zero
Answer: equal.
(20) In binary system III represents:
[A] 1
[B] 3
[C] 7
[D] 100
Answer: 7

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