Q.1
The voltage drop between the anode and cathode, of a mercury arc rectifier comprises of the following
  • anode drop and cathode drop
  • anode drop and arc drop
  • cathode drop and arc drop
  • anode drop, cathode drop and arc drop
Q.2
In a mercury arc rectifier______ flow from anode to cathode
  • ions
  • electrons
  • ions and electrons
  • any of the above
Q.3
In a rotary converter armature currents are
  • d.c. only
  • a.c. only
  • partly a.c. and partly d.c.
  • none of the above
Q.4
The cathdde voltage drop, in a mercury arc rectifier, is due to
  • expenditure of energy in ionization
  • surface resistance
  • expenditure of energy in overcoming the electrostatic field
  • expenditure of energy in liberating electrons from the mercury
Q.5
The ignited or auxiliary anode in mercury arc rectifier is made of
  • Graphite
  • Boron carbide
  • Aluminium
  • Copper
Q.6
The internal efficiency of a mercury arc rectifier depends on
  • voltage only
  • current only
  • voltage and current
  • r.m.s. value of current
  • E. none of the above
Q.7
In a mercury arc rectifier positive ions are attracted towards
  • anode
  • cathode
  • shell bottom
  • mercury pool
Q.8
The metal rectifiers, as compared to mercury arc rectifiers
  • operate on low temperatures
  • can operate on high voltages
  • can operate on heavy loads
  • give poor regulation
  • E. none of the above
Q.9
In selenium rectifiers efficiencies ranging from ______ to ______ percent are attainable
  • 25, 35
  • 40, 50
  • 60, 70
  • 75, 85
Q.10
The potential drop in the arc, in a mercury arc rectifier, varies
  • 0.05 V to 0.2 V per cm length of the arc
  • 0.5 V to 1.5 V per cm length of the arc
  • 2 V to 3.5 V per cm length of the arc
  • none of the above
Q.11
The advantage of mercury arc rectifier is that
  • it is light in weight and occupies small floor space
  • it has high efficiency
  • it has high overload capacity
  • it is comparatively noiseless
  • E. all of the above
Q.12
Which of the following AC. motors is usually used in large motor-generator sets?
  • Synchronous motor
  • Squirrel cage induction motor
  • Slip ring induction motor
  • Any of the above
Q.13
Glass rectifiers are usually made into units capable of D.C. output (maximum continuous rating) of
  • 100 A at 100 V
  • 200 A at 200 V
  • 300 A at 300 V
  • 400 A at 400 V
  • E. 500 A at 500 V
Q.14
Which of the following are the applications of D.C. system?
  • Battery charging work
  • Arc welding
  • Electrolytic and electro-chemical processes
  • Arc lamps for search lights
  • E. All of the above
Q.15
In mercury arc rectifiers having grid, the arc can be struck between anode and cathode only when the grid attains a certain potential, this potential being known as
  • maximum grid voltage
  • critical grid voltage
  • any of the above
  • none of the above
Q.16
Copper oxide rectifier is usually designed not to operate above
  • 10°C
  • 20°C
  • 30°C
  • 45°C
Q.17
In a mercury arc rectifier characteristic blue luminosity is due to
  • colour of mercury
  • ionization
  • high temperature
  • electron streams
Q.18
The metal rectifiers are preferred to valve rectifiers due to which of the following advantages ?
  • They are mechanically strong
  • They do not require any voltage for filament heating
  • Both (A) and (B)
  • None of the above
Q.19
The applications of selenium rectifiers are usually limited to potential of
  • 10 V
  • 30 V
  • 60 V
  • 100 V
  • E. 200 V
Q.20
A rotary converter in general construction and design, is more or less like
  • a transformer
  • an induction motor
  • an alternator
  • any ' machine
Q.21
In a glass bulb mercury arc rectifier the maximum current rating is restricted to
  • 2000 A
  • 1500 A
  • 1000 A
  • 500 A
Q.22
In a rotary converter Ilosses as compared to a D.C. generator of the same size will be
  • same
  • less
  • double
  • three times
Q.23
Ageing of a selenium rectifier may change the output voltage by
  • 5 to 10 per cent
  • 15 to 20 per cent
  • 25 to 30 per cent
  • none of the above
Q.24
Which of the following rectifiers are primarily used for charging of low voltage batteries from AC. supply?
  • Mechanical rectifiers
  • Copper oxide rectifiers
  • Selenium rectifiers
  • Electrolytic rectifiers
Q.25
The efficiency of the copper oxide rectifier seldom exceeds
  • 90 to 95%
  • 85 to 90%
  • 80 to 85%
  • 65 to 75%
Q.26
A rotary converter combines the function of
  • an induction motor and a generator
  • a synchronous motor and a generator
  • a
  • none of the above
Q.27
In a three-phase mercury arc rectifiers each anode conducts for
  • One-third of a cycle
  • One-fourth of a cycle
  • One-half a cycle
  • Two-third of a cycle
Q.28
Which of the following rectifiers have been used extensively in supplying direct current for electroplating?
  • Copper oxide rectifiers
  • Selenium rectifiers
  • Mercury arc rectifiers
  • Mechanical rectifiers
  • E. None of the above
Q.29
In a single phase rotary converter the number of slip rings will be
  • two
  • three
  • four
  • six
Q.30
A synchronous converter can be started
  • by means of a small auxiliary motor
  • from side as induction motor
  • from side as motor
  • any of the above methods
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