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

Questions
1 A p-type semiconductor is:
A negatively charged3
B positively charged
C uncharged
D None of these

Answer:uncharged
2 Zener diode is used for:
A producing oscillations in a oscillator
B amplification
C stabilisation
D rectification

Answer:stabilisation

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3 In full wave rectifier, input a.c. current has a frequency v. The output frequency of current is :
A V/2
B V
C 2V
D None

Answer:2V
4 In semi conductor, at room temperature :
A the valence bond is partially empty and the conduction band is partially filled
B the valence band is completely filled and the conduction band is partially filled
C the valence band is completely filled
D the conduction band is completely empty

Answer:the valence bond is partially empty and the conduction band is partially filled
5 Bonds in a semiconductor :
A trivalent
B covalent
C bivalent
D monovalent

Answer:covalent
6 The part of a transistor which is heavily doped to produce a large number of majority carriers is :
A base
B emitter
C collector
D None of these

Answer:emitter
7 What is the number of possible crystal systems?
A 5
B 7
C 14
D 16

Answer:7
8 The cause of the potential barrier in a p-n junction diode is
A depletion of positive charges near the junction3
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:concentration of positive and negative charges near the junction
9 Reverse bias applied to a junction diode
A increases the minority carrier current
B lowers the potential barrier
C raises the potential barrier
D increases the majority carrier current

Answer:raises the potential barrier
10 In a semiconductor diode, the barrier potential offers opposition to
A holes in P-region only
B free electrons in N-region only
C majority carriers in both regions
D majority as well as minority carriers in both regions

Answer:majority carriers in both regions
11 Filter circuit
A eliminates a.c. component
B eliminates d.c. component
C does not eliminate a.c. component
D None of these

Answer:eliminates a.c. component
12 In V-I characteristic of a p-n junction, reverse biasing results in
A leakage current
B the current barrier across junction increases
C no flow of current
D large current

Answer:leakage current
13 Diffusion current in a p-n junction is greater than the drift current in magnitude)
A if the junction is forward-biased
B if the junction is reverse-biased
C if the junction is unbiased
D in no case

Answer:if the junction is forward-biased
14 The drift current in a p-n junction is from the
A n-side to the p-side
B p-side to the n-side
C n-side to the p-side if the junction is forward-biased and in the opposite direction if it is reverse biased
D p-side to the n-side if the junction is forward-biased and in the opposite direction if it is reverse-biased

Answer:n-side to the p-side
15 A semiconductor device is connected in a series circuit with a battery and a resistance. A current is found to pass through the circuit. If the polarity of the battery is reversed, the current drops to almost zero. The device may be a/an
A intrinsic semiconductor
B p-type semiconductor
C n-type semiconductor
D p-n junction diode

Answer:p-n junction diode
16 A strip of copper and another of germanium are cooled from room temperature to 80K. The resistance of
A each of these decreases
B copper strip increases and that of germanium decreases
C copper strip decreases and that of germanium increases
D each of these increases

Answer:copper strip decreases and that of germanium increases
17 The diffusion current in a p-n junction is from the
A n-side to the p-side
B p-side to the n-side
C n-side to the p-side if the junction is forward-biased and in the opposite direction if it is reverse-biased
D p-side to the n-side if the junction is forward-biased and in the opposite direction if it is reverse-biased

Answer:p-side to the n-side
18 If the two ends of a p-n junction are joined by a wire
A there will not be a steady current in the circuit
B there will be a steady current from the n-side to the p side
C there will be a steady current from the p-side to the n side
D there may or may not be a current depending upon the resistance of the connecting wire

Answer:there will not be a steady current in the circuit
19 Forward biasing is that in which applied voltage
A increases potential barrier
B cancels the potential barrier
C is equal to 1.5 volt
D None of these

Answer:cancels the potential barrier
20 If a small amount of antimony is added to germanium crystal
A it becomes a p–type semiconductor
B the antimony becomes an acceptor atom
C there will be more free electrons than holes in the semiconductor
D its resistance is increased

Answer:there will be more free electrons than holes in the semiconductor

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