NEET Physics Semiconductor and P N Junction Diode MCQs Set A

Question. In a semiconductor
(a) there are no free electrons at 0 K
(b) there are no free electrons at any temperature
(c) the number of free electrons increases with pressure
(d) the number of fre electrons is more than that in a conductor

Answer: A

Question. The electrical conductivity of pure germanium can be increased by
(a) All of the above
(b) doping donor impurities
(c) doping acceptor impurities
(d) increasing the temperature

Answer: A

Question. Electric conduction in a semiconductor takes place due to
(a) both electrons and holes
(b) neither electrons nor holes
(c) holes only
(d) electrons only

Answer: A

Question. A p-type semiconductor is
(a) uncharged
(b) uncharged at 0K but charged at higher temperatures
(c) positively charged
(d) negatively charged

Answer: A

Question. The impurity atoms with which pure silicon may be doped to make it a p-type semiconductor are those of
(a) boron
(b) nitrogen
(c) phosphorus
(d) antimony

Answer: A

Question. When an impurity is doped into an intrinsic semiconductor, the conductivity of the semiconductor
(a) remains the same
(b) decreases
(c) increases
(d) becomes zero

Answer: A

Question. The ratio of forward biased to reverse biased resistance for pn junction diode is
(a) 10–1 : 1
(b) 10–2 : 1
(c) 10–4 : 1
(d) None of these

Answer: A

Question. A strip of copper and another of germanium are cooled from room temperature to 80K. The resistance of
(a) copper strip decreases and that of germanium increases
(b) each of these increases
(c) copper strip increases and that of germanium decreases
(d) each of these decreases

Answer: A

Question. 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: A

Question. If a small amount of antimony is added to germanium crystal
(a) there will be more free electrons than holes in the semiconductor
(b) its resistance is increased
(c) the antimony becomes an acceptor atom
(d) it becomes a p–type semiconductor

Answer: A

Question. 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: A

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

Answer: A

Question. A half-wave rectifier is being used to rectify an alternating voltage of frequency 50 Hz. The number of pulses of rectified current obtained in one second is
(a) 25
(b) 100
(c) 2000
(d) 50

Answer: A