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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