300+ TOP SCR Questions and Answers Pdf | MCQs

SILICON CONTROLLED RECTIFIERS Questions :-

1. An SCR has …………….. pn junctions

1. Two
2. Three
3. Four
4. None of the above
   ANS : 2

2. An SCR is a solid state equivalent of …………….

1. Triode
2. Pentode
3. Gas-filled triode
4. Tetrode
   ANS : 3

3. An SCR has ………….. semiconductor layers

1. Two
2. Three
3. Four
4. None of the above
   ANS : 3

4. An SCR has three terminals viz ……………

1. Cathode, anode, gate
2. Anode, cathode, grid
3. Anode, cathode, drain
4. None of the above
   ANS : 1

5. An SCR behaves as a ……………. switch

1. Unidirectional
2. Bidirectional
3. Mechanical
4. None of the above
   ANS : 1

6. An SCR is sometimes called …………

1. Triac
2. Diac
3. Unijunction transistor
4. Thyristor
   ANS : 4

7. An SCR is made of ………….

1. Germanium
2. Silicon
3. Carbon
4. None of the above
   ANS : 2

8. In the normal operation of an SCR, anode is …………… w.r.t. cathode

1. At zero potential
2. Negative
3. Positive
4. None of the above
   ANS : 3

9. In normal operation of an SCR, gate is ………..w.r.t. cathode

1. Positive
2. Negative
3. At zero potential
4. None of the above
   ANS : 1

10. An SCR combines the features of …………..

1. A rectifier and resistance
2. A rectifier and transistor
3. A rectifier and capacitor
4. None of the above
   ANS : 2

11. The control element of an SCR is ………….

Cathode
Anode
Anode supply
Gate
ANS : 4

12. The normal way to turn on a SCR is by ……………..

Breakover voltage
Appropriate anode current
Appropriate gate current
None of the above
ANS : 3

13. An SCR is turned off by …………….

Reducing anode voltage to zero
Reducing gate voltage to zero
Reverse biasing the gate
None of the above
ANS : 1

14. An SCR is a ……………….. triggered device

Voltage
Current
Voltage as well as current
None of the above
ANS : 2

15. In an SCR circuit the supply voltage is generally ……….. that of breakover voltage

Equal to
Less than
Greater than
None of the above
ANS : 2

16. When an SCR is turned on, the voltage across it is about ……….

Zero
10 V
1 V
1 V
ANS : 4

17. An SCR is made of silicon and not germanium because silicon ………

Is inexpensive
Is mechanically strong
Has small leakage current
Is tetravalent
ANS : 3

18. An SCR is turned off when …………..

Anode current is reduced to zero
Gate voltage is reduced to zero
Gate is reverse biased
None of the above
ANS : 1

19. In an SCR circuit, the angle of conduction can be changed by ……….

Changing anode voltage
Changing gate voltage
Reverse biasing the gate
None of the above
ANS : 2

20. If firing angle in an SCR circuit is increased, the output …………

Remains the same
Is increased
Is decreased
None of the above
ANS : 3

21. If gate current is increased, then anode-cathode voltage at which SCR closes …………….

Is decreased
Is increased
Remains the same
None of the above
ANS : 1

22. When SCR is OFF, the current in the circuit is …………….

Exactly zero
Small leakage current
Large leakage current
None of the above
ANS : 2

23. An SCR can exercise control over ………. of a.c. supply

Positive half-cycles only
Negative half-cycles only
Both positive and negative half-cycles
Positive or negative half-cycles
ANS : 4

24. We can control a.c. power in a load by connecting …………

Two SCRs in series
Two SCRs in parallel
Two SCRs in parallel opposition
None of the above
ANS : 3

25. When SCR starts conducting, then ……………. loses all control

Gate
Cathode
Anode
None of the above
ANS : 1

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