57. UJT when used for triggering an SCR, has wave form,
A. sine wave
B. square wave
C. saw tooth wave
D. trapezoidsl

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58. A resistor connected across the gate and cathode of a thyristor increases its
A. turn offtime
B.drain
C. noise immunity
D. holding current

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59. Inverter converts
A. dc to ac
B. ac to ac
C. dc to dc
D. ac to ac

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60. In series connected thyrstors
A. L, is used for tuning out junction capacitance
B. L & C is used for filtering out the ripple
C. R, C iscalled a snubber act.di
D. L is intended to increase ? at switch dt on

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61. When a thyristor and transistor as a switch are compared, true statement is
A. thyristor requires turn off circuit while transistor does not
B.the voltagedrop of thyristor is less than transistor
C. thyristor requires a continuous gate current
D. transistor does not draw continuously base current

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62. In dc choppers, the waveforms for input and output voltages are respectively
A. both discontinuous
B. both continuous
C. continuous, discontinuous
D. discontinuous, continuous

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63. In dc choppers, per unit apple is maximum whenduty cycle a is
A.0.1
B.0.3
C.0.5
D.0.7

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