Latest Rectifiers and Converters Multiple choice Questions and Answers pdf

31.    In a three-phase mercury arc rectifiers each anode conducts for
(a)     one-third of a cycle
(b)     one-fourth of a cycle
(c)    one-half a cycle
(d)    two-third of a cycle
Ans: a

32.    In a mercury arc rectifier characteristic blue luminosity is due to
(a)     colour of mercury
(b)     ionization
(c)    high temperature
(d)    electron streams
Ans: b

33.    Which of the following mercury arc rectifier will deliver least undulating current?
(a) Six-phase 
(b) Three-phase
(c) Two-phase 
(d) Single-phase
Ans: a

34.    In a glass bulb mercury arc rectifier the maximum current rating is restricted to
(a) 2000 A 
(b) 1500 A
(c) 1000 A 
(d) 500 A
Ans: d

35.    In a mercury arc rectifier______ flow from anode to cathode
(a) ions 
(b) electrons
(c) ions and electrons
(d) any of the above
Ans: a

36.    When a rectifier is loaded which of the following voltage drops take place ?
(a)     Voltage drop in transformer reactance
(6)     Voltage drop in resistance of transformer and smoothing chokes
(c)    Arc voltage drop
(d)    All of the above
Ans: d

37.    On which of the following factors the number of phases for which a rectifier should be designed depend ?
(a)     The voltage regulation of the rec¬tifier should be low
(b)     In the output circuit there should be no harmonics
(c)    The power factor of the system should be high
(d)    The rectifier supply transformer should be utilized to the best ad-vantage
(e)    all of the above
Ans: e

38.    A mercury arc rectifier possesses ________ regulation characteristics
(a)     straight line   
(b)     curved line
(c)    exponential
(d)    none of the above
Ans: d

39.    It is the_______of the transformer on which the  magnitude  of angle of overlap depends.
(a) resistance
(b) capacitance
(c) leakage reactance
(d) any of the above
Ans: c

40.    In a grid control of mercury arc rectifiers when the grid is made positive relative to cathode, then it      the electrons on their may to anode.
(a)     accelerates    
(b)     decelerates
(c)    any of the above
(d)    none of the above
Ans: a

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