This set of Engineering Physics Multiple Choice Questions & Answers (MCQs) focuses on “Characteristics of P-N Junction”.
1. In a P-N Junction, the depletion region is reduced when _________
a) P side is connected to the negative side of the terminal
b) P side is connected to the positive side of the terminal
c) N side is connected to the positive side of the terminal
d) Never reduced
Explanation: When the P-side of a P-N junction is connected to the positive terminal of a battery, the junction is forward biased and hence the depletion region reduces.
2. The voltage at which forward bias current increases rapidly is called as ___________
a) Breakdown Voltage
b) Forward Voltage
c) Knee Voltage
d) Voltage barrier
Explanation: Till the knee voltage, the current in a semiconductor increases slowly. After Knee voltage, the current increases rapidly for a small change in the voltage.
3. The Knee Voltage for germanium is _________
a) 0.1 V
b) 0.3 V
c) 0.7 V
d) 1.4 V
Explanation: Knee voltage or the threshold voltage is the point after which the current increases rapidly. For germanium, it is about 0.3 V while for silicon it is 0.7 V.
4. The resistance of the semiconductor decreases in forward biased.
Explanation: When a P-N Junction diode is forward biased, the thickness of the depletion region becomes negligibly small. Thus, the resistance of the semiconductor decreases.
5. The current produced in reverse-bias is called as __________
a) Reverse Current
b) Breakdown Current
c) Negative Current
d) Leakage Current
Explanation: When the diode is reverse biased, the reverse bias voltage produces an extremely small current, about a few micro amperes. This is called leakage current.
6. Which diode is designed to work under breakdown region?
b) Light Emitting Diode
c) Solar Cell
d) Zener diode
Explanation: Zener Diode is designed specifically to operate in the breakdown region. It is mostly used as a voltage regulator in various circuits.
7. The P-N junction is a non-ohmic device.
Explanation: The current-voltage curve of a P-N junction diode is not a straight line. Thus, it does not obey Ohm’s law and is a non-ohmic device.
Explanation: The current at 2 V is 5 mA and at 2.2 V it is 10 mA.
The dynamic resistance is: Δ V/Δ I
= 0.5/5 X 103 Ω
= 40 Ω.
9. The leakage current is measured in ________
Explanation: As in the reverse current, the resistance increases, the current produced is extremely low. And hence, it is measured in microamperes.
Explanation: From the curve, I = 20 mA, V = 0.8 V, I = 10 mA when V = 0.7 V
Now, R = Δ V/Δ I
= 0.1 V/10 mA
= 10 Ω.
Sanfoundry Global Education & Learning Series – Engineering Physics.
To practice all areas of Engineering Physics, here is complete set of 1000+ Multiple Choice Questions and Answers.