Q.1
To produce cathode spot in a mercury arc rectifier
  • anode is heated
  • tube is evacuated
  • an auxiliary electrode is used
  • low mercury vapour pressures are used
Q.2
If cathode and anode connections in a mercury arc rectifier are inter changed
  • The rectifier will not operate
  • Internal losses will be reduced
  • Both ion and electron streams will move in the same direction
  • The rectifier will operate at reduced efficiency
Q.3
Which of the following metals is generally manufactured by electrolysis process?
  • Load
  • Aluminium
  • Copper
  • Zinc
  • E. None of the above
Q.4
In a mercury arc rectifier, the anode is usually made of
  • copper
  • aluminium
  • silver
  • graphite
  • E. tungsten
Q.5
When a rectifier is loaded which of the following voltage drops take place ?
  • Voltage drop in transformer reactance
  • Voltage drop in resistance of transformer and smoothing chokes
  • Arc voltage drop
  • All of the above
Q.6
In a mercury pool rectifier, the voltage drop across its electrodes
  • is directly proportional to load
  • is inversely proportional to load
  • varies exponentially with the load current
  • is almost independent of load current
Q.7
In a phase-shift control method, the phase shift between anode and grid voltages can be achieved by means of
  • Shunt motor
  • Synchronous motor
  • Induction regulator
  • Synchronous generator
Q.8
Which of the following methods may be used to convert A.C. system to D.C.?
  • Rectifiers
  • Motor converters
  • Motor-generator sets
  • Rotary converters
  • E. All of the above
Q.9
On which of the following factors the number of phases for which a rectifier should be designed depends?
  • The voltage regulation of the rectifier should be low
  • In the output circuit there should be no harmonics
  • The power factor of the system should be high
  • All of the above
Q.10
With a motor converter it is possible to obtain D.C. voltage only upto
  • 200-100 V
  • 600-800 V
  • 1000-1200 V
  • 1700-2000 V
Q.11
A commutating rectifier consists of commutator driven by
  • An induction motor
  • A synchronous motor
  • A series motor
  • A shunt motor
Q.12
The voltage drop at anode, in a mercury arc rectifier is due to
  • self restoring property of mercury
  • high ionization potential
  • energy spent in overcoming the electrostatic field
  • high temperature inside the rectifier
Q.13
The efficiency of an electrolytic rectifier is nearly
  • 80%
  • 70%
  • 60%
  • 40%
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