This set of FACTS Multiple Choice Questions & Answers (MCQs) focuses on “Diode PN Junction & Transistor”.
1. Diode is a/an ________ circuit element.
a) bidirectional
b) unidirectional
c) linear
d) multidirectional
View Answer
Explanation: Diode is a unidirectional circuit element because it conducts in one direction with low resistance during forward bias. During reverse bias it blocks or stops conducting. Because of its inherent property of unidirectional conduction, it finds use in various applications of FACTS.
2. BJT is an acronym for ________
a) Bipolar Junction transistor
b) Bipolar Junction thyristor
c) Bipolar Junction transmitter
d) Bypass Junction transistor
View Answer
Explanation: BJT is an acronym for Bipolar Junction transistor. It is characterized by three parts of alternative positive and negative polarity, separated by two junctions. The three parts are doped differently as per the configuration needed.
3. A bipolar junction transistor is a/an ________
a) independent voltage source
b) independent current source
c) dependent voltage source
d) dependent current source
View Answer
Explanation: By dint of its characteristic feature, a bipolar junction transistor can be represented as a dependent current source. In a BJT the magnitude of the current depends on that magnitude of current which is fed into its controlling base terminal. The characteristic feature of BJT is dissimilar to that of a thyristor.
4. Like an operational amplifier, a BJT is also a voltage source.
a) True
b) False
View Answer
Explanation: In a BJT the magnitude of the current is controlled by that magnitude of current which is fed into its controlling base terminal. Hence BJT may be considered as a current source dependent on base current. On the other hand, an operational amplifier can be represented only as a voltage source dependent on the differential input voltage between its input terminals.
5. MOSFET is the abbreviation of ________
a) Metal-Oxide Semiconductor Field Effect Transistor
b) Metal-Oxide Semiconductor Field Effect Thyristor
c) Metal-Oxide Semi-active Field Effect Transistor
d) Metal-Oxide Semi-passive Field Effect Transistor
View Answer
Explanation: MOSFET is the abbreviation of Metal-Oxide Semiconductor Field Effect Transistor. This type of transistor exhibits fast switching and low switching losses. Hence it is applied with other devices in various applications in FACTS.
6. MOSFET is an example of a passive switch.
a) True
b) False
View Answer
Explanation: MOSFET is NOT an example of a passive switch. It is an active switch. This is because its switching on or off, is controlled by its third terminal which is gate.
7. Diode is ________ switch.
a) an active
b) a passive
c) a semi-passive
d) a semi-active
View Answer
Explanation: Diode is a passive switch. This is so because a diode can be controlled to conduct by simply controlling the voltage applied at its two terminals. It does not have any third terminal exclusively available for its controlling.
8. Choose the right option among the alternatives–The inherent property of a diode is to exhibit positive on-state/off-state conduction of current and negative on-state/ off-state blocking of voltage.
a) On-state, off-state
b) On-state, on-state
c) Off-state, on-state
d) Off-state, off-state
View Answer
Explanation: The inherent property of a diode is to exhibit positive on-state conduction of current and negative off-state blocking of voltage. However, to fit any diode as a switch, the intended on-state and off-state operating points of the switch must lie on the V-I characteristic graph of that diode. A diode can function as a SPST switch.
9. Choose the right option among the alternatives – The inherent property of a BJT is to exhibit positive/negative on-state conduction of current and positive/negative off-state blocking of voltage.
a) Positive, negative
b) Positive, negative
c) Negative, negative
d) Positive, positive
View Answer
Explanation: The inherent property of a BJT is to exhibit positive on-state conduction of current and positive off-state blocking of voltage. Like diode, BJT also shows single-quadrant operation. IGBT also shares the same property of single-quadrant operation.
10. FET is the abbreviation of ________
a) Field Effect Transistor
b) Field Effect Thyristor
c) Field Effect Thermistor
d) Field Effect Thermostat
View Answer
Explanation: FET is the abbreviation of Field Effect Transistor. It can be JFET or MOSFET. Compared to the JFET, MOSFETs are easier to fabricate.
11. Which of the following comes with an integral body diode?
a) Resistor
b) Inductor
c) Capacitor
d) MOSFET
View Answer
Explanation: Resistor, Capacitor, Inductor do not come with an integral body diode. MOSFET does come with an integral body diode. For this integral diode, MOSFET can indulge in allowing bi-directional current flow through it.
12. PN junction diode is an example of a bipolar device.
a) True
b) False
View Answer
Explanation: PN junction diode is an example of a bipolar device. This is because in a diode both holes and electrons took part in the conduction when the diode is made to conduct. Thus, both positive and negative polarity particles are essential in its conduction.
13. Diode is a ________ device.
a) single junction
b) double junction
c) triple junction
d) quadruple junction
View Answer
Explanation: Diode is a single junction device with p and n layers. P layer contains holes with positive charges. N layer contains electrons with negative charges. These layers are done with proper doping in a single wafer.
14. A diode is connected ________ turn-off thyristor.
a) always in parallel to
b) always in series with
c) either in parallel to or in series with
d) neither in parallel to nor in series with
View Answer
Explanation: A diode is connected either in parallel to or in series with turn-off thyristor. This is as per the requirement of design of the circuit. In voltage-sourced converters a diode is connected across each turn-off thyristor, i.e. in parallel but in the reverse direction. Again, for reverse blocking of voltage, a diode is connected in series with each turn-off thyristor.
15. _______ are used in snubber circuits.
a) Diodes
b) Transistors
c) Thyristors
d) SCRs
View Answer
Explanation: Diodes are used in snubber circuits. They are also used in gate-drive circuits. The property of unidirectional conduction of current of a pn diode is employed in such applications.
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