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1. Which of the following equipment may be used to check the condition of a diode?
a) Digital Display Meter
b) Ohmmeter
c) Curve Tracer
d) All of the mentioned

View Answer

Answer: d [Reason:] All the methods may be used to test a diode for its proper functioning.

2. What is the expected reading obtained on a Digital Display Meter with diode-checking function when a proper functioning silicon semiconductor diode is connected across its leads in the forward bias configuration?
a) 0.67 V
b) 0.3 V
c) Open Loop Indication
d) Varies with the diode

View Answer

Answer: a [Reason:] The diode checking function on the meter when used causes a current of 2 mA to flow through the diode and hence under forward bias, the voltage is determined to be 0.67 V.

3. What is the expected reading obtained on a Digital Display Meter with diode-checking function when a proper functioning silicon semiconductor diode is connected across its leads in the reverse bias configuration?
a) 0.67 V
b) 0.3 V
c) Open Loop Indication
d) Varies with the diode

View Answer

Answer: c [Reason:] The diode checking function on the meter when used causes a current of 2 mA to flow through the diode and hence under reverse bias, the result obtained is the open loop indication.

4. A diode on being checked by a DDM with diode checking function results in an open loop indication in both directions. Which of the following is the correct inference drawn from the given situation?
a) Power failure to the DDM
b) Diode is faulty
c) Diode is proper
d) None of the mentioned

View Answer

Answer: b [Reason:] A diode allows electrical conduction in just one direction. Hence, if an instrument shows open loop indication in both the directions, then the diode is faulty.

5. A silicon semiconductor diode when subjected to ohmmeter testing gives low resistance in both the directions. Which of the following is the correct inference to be drawn?
a) Diode is faulty
b) Power failure to the Ohmmeter
c) Diode is short-circuited
d) Can’t be determined

View Answer

Answer: c [Reason:] A proper diode gives a low resistance reading along one direction and high resistance reading along the other. Hence, if diode gives low resistance readings in both the directions, then the diode must be short-circuited. It’s noteworthy that a faulty diode gives a high resistance reading along both the paths.

6. A silicon semiconductor diode when subjected to ohmmeter testing gives high resistance in both the directions. Which of the following is the correct inference to be drawn?
a) Diode is faulty
b) Power failure to the Ohmmeter
c) Diode is short-circuited
d) Can’t be determined

View Answer

Answer: a [Reason:] A proper diode gives a low resistance reading along one direction and high resistance reading along the other. Hence, if diode gives high resistance readings in both the directions, then the diode must be faulty.

7. How can the location of the Zener region be controlled in the diode characteristic curve?
a) By changing the value of Iz
b) By changing the doping concentration of the diode
c) By changing the operating temperature
d) Can’t be changed

View Answer

Answer: b [Reason:] An increase in doping will lead to an increase in the concentration of impurities, which would further lead to a change in VZ and hence change in the Zener region.

8. Which material is generally used for the manufacture of Zener diode?
a) Silicon
b) Germanium
c) Mercury
d) None of the mentioned

View Answer

Answer: a [Reason:] Because of its high heat and current handling capacity, Silicon is generally used for the manufacture of Zener diodes.

9. Which of the following is not a part of the equivalent circuit of a Zener diode?
a) Dynamic Resistance
b) DC Battery
c) Ideal diode
d) None of the mentioned

View Answer

Answer: c [Reason:] The equivalent circuit diagram of a Zener diode doesn’t involve an ideal diode as it is used under reverse bias and an ideal diode doesn’t conduct under reverse bias.

10. At 298 K, the nominal Zener voltage is found to be equal to 10 V. Given that the value of Temperature coefficient is 0.072 (%/K), what is the nominal Zener Voltage at 398 K?
a) 9.46 V
b) 9.54 V
c) 0.54 V
d) 10.54 V

View Answer

Answer: d [Reason:] The change in VZ with temperature is calculated from the following equation: Change in VZ = TC.VZ(T1 – T0))/1000 Change in VZ = 0.54 V Now, as the value of T ¬is positive, new VZ = 10 + 0.54 V = 10.54 V

11. Which of the following materials is used to make LEDs?
a) Silicon
b) GaAsP
c) Germanium
d) All of the mentioned

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Answer: b [Reason:] In Silicon and Germanium, the major chunk of energy is given off as heat the hence the emitted light isn’t significant. In Gallium Arsenide Phosphide (GaAsP), the number of photons are enough to create a visual source of light.

12. Which of the following voltages may be considered as a safe and sufficient voltage for the operation of a LED?
a) 0.7 V
b) 5 V
c) 2.7 V
d) -5 V

View Answer

Answer: c [Reason:] The safe and sufficient operating voltage range for LED is between 1.7 V to 3.3 V. Hence, 2.7 V is the best option.

13. What is the order of magnitude of the response time of LED?
a) 10-6
b) 10-9
c) 10-15
d) 10-3

View Answer

Answer: b [Reason:] The response time of a LED is typically in the order of nanoseconds.

14. Which of the following is an advantage of using a LED?
a) Low response time
b) Compatibility with solid-state circuits
c) Rugged construction and high lifetime
d) All of the mentioned

View Answer

Answer: d [Reason:] The response time of a LED is typically in the order of nanoseconds. The operating voltage range for LED is between 1.7 V to 3.3 V which makes it compatible with solid-state circuits. Also, the semiconductor construction makes them rugged.

15. A LED will glow, if connected under reverse bias configuration:
a) True
b) False

View Answer

Answer: b [Reason:] A Light Emitting Diode works just like any other diode and hence it does not conduct under reverse bias operation and hence the LED will not glow.