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ECE Objective Questions { Power Semiconductor Devices and Their Applications }

50.  In single-phase full-wave controlled bridge rectifier, minimum output voltage is obtained at conduction angle and maximum at conduction angle
A. 0?, 1800
B. 180?, 0?
C. 0?, 0?
D. 180?, 180?

51.  In a thyristor
A. the holding current is greater than latching current
B. the two currents are equal
C. the latching current is about 3 times the holding current
D. none of the above

52. The VI characteristics of UJT is
A. similar to CE with a linear and saturation region
B.similar to FET with a linear and pinch off region
C. similar to tunnel diode in some respects
D. similar to pn junction diode in some respects.

53. Chopper control for DC motor provides variation in
A. input voltage
B. frequency
C. none of the above
D. current

54. In a thyristor the ratio of latching current to holding current is

55. In a thyristor, ?dt protection is achieved through the use of
A. L across thyristor
B. R acrossthyristor
C. RC across thyristor
D. RL across thyristor di

56. In a thyristor ?dt protection is achieved through the use of
A. L in series with thyristor
B. R in series with thyristor
C. RC in series with thyristor
D. RL in series with thyristor

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