scr silicon controlled rectifiers Mcqs
1. We can control a.c. power in a load by connecting ______________?
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A. Two SCRs in parallel

B. None of the above

C. Two SCRs in parallel opposition

D. Two SCRs in series

2. An SCR can exercise control over____________of a.c. supply?
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A. Positive half-cycles only

B. Negative half-cycles only

C. Both positive and negative half-cycles

D. Positive or negative half-cycles
3. An SCR combines the features of ____________?
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A. A rectifier and resistance

B. None of the above

C. A rectifier and capacitor

D. A rectifier and transistor
4. An SCR behaves as a____________switch?
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A. Bidirectional

B. Mechanical

C. Unidirectional

D. None of the above

5. An SCR has __________ pn junctions?
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A. Two

B. Four

C. None of the above

D. Three
6. An SCR is sometimes called ____________?
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A. Diac

B. Triac

C. Unijunction transistor

D. Thyristor
7. An SCR is turned off by _________________?
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A. None of the above

B. Reverse biasing the gate

C. Reducing gate voltage to zero

D. Reducing anode voltage to zero
8. An SCR is a solid state equivalent of ______________?
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A. Tetrode

B. Triode

C. Gas-filled triode

D. Pentode

9. An SCR is a ____________ triggered device?
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A. Voltage

B. None of the above

C. Current

D. Voltage as well as current

10. An SCR has three terminals viz ________________?
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A. Anode, cathode, grid

B. Cathode, anode, gate

C. None of the above

D. Anode, cathode, drain

11. When an SCR is turned on, the voltage across it is about _____________?
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A. 1 V

B. 1 V

C. 10 V

D. Zero

12. An SCR has ___________semiconductor layers?
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A. None of the above

B. Three

C. Two

D. Four
13. When SCR starts conducting, then _____________ loses all control?
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A. Anode

B. None of the above

C. Gate

D. Cathode

14. If firing angle in an SCR circuit is increased, the output _____________?
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A. None of the above

B. Remains the same

C. Is decreased

D. Is increased

15. In normal operation of an SCR, gate is _____________w.r.t. cathode?
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A. None of the above

B. At zero potential

C. Negative

D. Positive
16. When SCR is OFF, the current in the circuit is ________________?
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A. None of the above

B. Exactly zero

C. Small leakage current

D. Large leakage current

17. In an SCR circuit the supply voltage is generally ___________ that of breakover voltage?
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A. Equal to

B. Greater than

C. None of the above

D. Less than
18. The control element of an SCR is ______________?
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A. Anode

B. Anode supply

C. Gate

D. Cathode

19. In an SCR circuit, the angle of conduction can be changed by__________________?
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A. None of the above

B. Changing gate voltage

C. Reverse biasing the gate

D. Changing anode voltage

20. An SCR is made of_______________?
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A. Germanium

B. None of the above

C. Carbon

D. Silicon
21. An SCR is turned off when ________________?
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A. Gate voltage is reduced to zero

B. None of the above

C. Anode current is reduced to zero

D. Gate is reverse biased

22. The normal way to turn on a SCR is by______________?
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A. Breakover voltage

B. None of the above

C. Appropriate gate current

D. Appropriate anode current

23. If gate current is increased, then anode-cathode voltage at which SCR closes_________________?
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A. Is increased

B. None of the above

C. Remains the same

D. Is decreased
24. An SCR is made of silicon and not germanium because silicon _________________?
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A. Is mechanically strong

B. Has small leakage current

C. Is tetravalent

D. Is inexpensive

25. In the normal operation of an SCR, anode is __________ w.r.t. cathode?
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A. Positive

B. Negative

C. At zero potential

D. None of the above