Here are 20 multiple-choice questions on PN junctions with correct answers indicated.
1. A PN junction diode is formed by joining:
a) Two p-type semiconductors
b) Two n-type semiconductors
c) P-type and N-type semiconductors
d) Intrinsic semiconductor
**Answer: c) P-type and N-type semiconductors** [1]
2. In a PN junction with no external voltage, the electric field between acceptor and donor ions is called a:
a) Peak
b) Barrier
c) Threshold
d) Path
**Answer: b) Barrier** [2]
3. The reverse saturation current in a PN junction diode is typically:
a) Few milliamperes
b) Between 0.2 A and 15 A
c) Few amperes
d) Few micro or nano amperes
**Answer: d) Few micro or nano amperes** [2]
4. When PN junction is in forward bias, by increasing the battery voltage:
a) Circuit resistance increases
b) Current through PN junction increases
c) Current through PN junction decreases
d) None of the above
**Answer: b) Current through PN junction increases** [2]
5. In forward bias, the positive terminal of the battery is connected to:
a) N-side
b) P-side
c) Either
d) None
**Answer: b) P-side and negative to N-side** [2]
6. PN junction failure below 5 V is caused primarily by:
a) Avalanche breakdown
b) Zener breakdown
c) Either (a) or (b)
d) None of the above
**Answer: b) Zener breakdown** [2]
7. In a reverse-biased PN junction, current increases abruptly at:
a) 0.5 V
b) 1.1 V
c) 0.72 V
d) Breakdown voltage
**Answer: d) Breakdown voltage** [2]
8. In forward bias, reduction in potential barrier occurs due to:
a) Widening of depletion region
b) Narrowing of depletion region
c) No change in depletion region
d) Increase in barrier height
**Answer: b) Narrowing of depletion region** [3]
9. The cut-in voltage for a silicon PN junction diode is about:
a) 0.2 V
b) 0.7 V
c) 1.1 V
d) 0.5 V
**Answer: b) 0.7 V** [4]
10. In reverse bias, the depletion region:
a) Narrows
b) Widens
c) Remains same
d) Disappears
**Answer: b) Widens** [4]
10 more
Here are 10 more multiple-choice questions on the PN junction with answers:
1. What happens to the depletion region width when the PN junction is forward biased?
a) It widens
b) It narrows
c) It disappears
d) No change
**Answer: b) It narrows** [1]
2. The barrier potential of a silicon PN junction diode is approximately:
a) 0.3 V
b) 0.5 V
c) 0.7 V
d) 1.0 V
**Answer: c) 0.7 V** [2]
3. Which current increases when a PN junction diode is forward biased?
a) Diffusion current
b) Drift current
c) Reverse saturation current
d) Leakage current
**Answer: a) Diffusion current** [3]
4. In a reverse-biased PN junction, the depletion layer:
a) Narrows
b) Broadens
c) Remains constant
d) Oscillates
**Answer: b) Broadens** [2]
5. When a PN junction diode breaks down at low reverse voltages, the mechanism is called:
a) Avalanche breakdown
b) Zener breakdown
c) Thermal breakdown
d) Electrical breakdown
**Answer: b) Zener breakdown** [4]
6. The minority carriers in the P-side of a PN junction are:
a) Electrons
b) Holes
c) Both electrons and holes
d) Neither
**Answer: a) Electrons** [2]
7. Forward voltage less than the barrier potential means:
a) The diode conducts heavily
b) The diode is off
c) Partial conduction
d) Reverse conduction occurs
**Answer: b) The diode is off** [5]
8. What type of charge carriers cross the junction in forward bias?
a) Majority carriers only
b) Minority carriers only
c) Both majority and minority carriers
d) No carriers
**Answer: c) Both majority and minority carriers** [5]
9. What happens to the potential barrier in a forward-biased PN junction?
a) It increases
b) It decreases
c) It remains unchanged
d) It becomes infinite
**Answer: b) It decreases** [1]
10. The primary function of a PN junction diode in circuits is:
a) Amplification
b) Rectification
c) Oscillation
d) Modulation
**Answer: b) Rectification** [2]
