29. The triac is
A. like a bidirectional SCR
B. a four-terminal device
C. not a thyristor
D. answer (i) and (ii)

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30. Which of the following device incorporates a terminal for synchronising purposes?
A. Disc
B. Triac
C. SUS
D. none of the above

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31. The advantage of thyristor over SCS is
A. slow switching time and large Vu
B. slow switching time and smaller VH
C. faster switching time and smaller VH
D. faster switching time and large VH.

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32. A thyristor equivalent of a thyratron tube is a
A. disc
B. triac
C. silicon controlled-rectifier SCR
D. done of the above

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33. A triac a
A. 2 terminal switch
B. 2 terminal bilateral switch
C. 3 terminal unilateral switch
D. 3 terminal bidirectional switch

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34. The tripple frequency of a six phase half wave rectifier for 220 V, 60 Hz input will be
A.2160 Hz
B. 720 Hz
C. 360 Hz
D. 60 Hz

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35. The minimum duration of pulse in a pulse triggering system for thyristors should be at least
A. 10 us
B. 10 ms
C. 30 ms
D. 1 sec

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