TOP Rectifiers and Converters Multiple choice Questions and Answers pdf

11.    A rotary converter in general construction and design, is more or less like
(a)     a transformer
(b)     an induction motor
(c)    an alternator
(d)    any D.C. machine
Ans: d

12.    A rotary converter operates at a
(a)  low power factor
(6)  high power factor
(c)  zero power factor
(d)  none of the above
Ans: b

13.    In which of the following appUcations, direct current is absolutely essential ?
(a)     Illumination  
(b)     Electrolysis
(c)    Variable speed operation
(d)    Traction
Ans: b

14.    Which of the following AC. motors is usually used in large motor-generator sets?
(a) Synchronous motor
(b) Squirrel cage induction motor
(c) Slip ring induction motor
(d) Any of the above
Ans: a

15.    In a rotary converter armature currents are
(a) d.c. only 
(b) a.c. only
(c) partly a.c. and partly d.c.
Ans: c

16.    In which of the following equipment direct current is needed ?
(a) Telephones    
(b) Relays
(c) Time switches
(d) All of the above
Ans: d

17.    In a rotary converter I2R losses as compared to a D.C. generator of the same size will be
(a) same 
(b) less
(c) double 
(d) three times
Ans: b

18.    In a mercury arc rectifier positive ions are attracted towards
(a) anode 
(b) cathode
(c) shell bottom   
(d) mercury pool
Ans: b

19.    Mercury, in arc rectifiers, is chosen for cathode because
(a) its ionization potential is relatively low
(b) its atomic weight is quite high
(c) its boiling point and specific heat are low
(d) it remains in liquid state at ordi¬nary temperature
(e) all of the above
Ans: e

20.    The ionization potential of mercury is approximately
(a) 5.4 V 
(b) 8.4 V
(c) 10.4 V 
(d) 16.4 V
Ans: c

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