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Electrical Engineering
Rectifiers And Converters
Quiz 2
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Q.1
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.2
The efficiency of the copper oxide rectifier seldom exceeds
90 to 95%
85 to 90%
80 to 85%
65 to 75%
Q.3
In a mercury arc rectifier______ flow from anode to cathode
ions
electrons
ions and electrons
any of the above
Q.4
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.5
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.6
A synchronous converter can be started
by means of a small auxiliary motor
from A.C. side as induction motor
from D.C. side as D.C. motor
any of the above methods
Q.7
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.8
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.9
In a mercury arc rectifier characteristic blue luminosity is due to
colour of mercury
ionization
high temperature
electron streams
Q.10
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.11
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.12
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.13
A rotary converter combines the function of
an induction motor and a D.C. generator
a synchronous motor and a D.C. generator
a D.
none of the above
Q.14
The efficiency of an electrolytic rectifier is nearly
80%
70%
60%
40%
Q.15
A rotary converter is a single machine with
one armature and one field
two armatures and one field
one armature and two fields
none of the above
Q.16
In a single phase rotary converter the number of slip rings will be
two
three
four
six
Q.17
A commutating rectifier consists of commutator driven by
An induction motor
A synchronous motor
A D.C. series motor
A D.C. shunt motor
Q.18
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.
accelerates
decelerates
any of the above
none of the above
Q.19
Which of the following mercury arc rectifier will deliver least undulating current?
Six-phase
Three-phase
Two-phase
Single-phase
Q.20
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
None of the above
Q.21
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.22
Which of the following metals is generally manufactured by electrolysis process?
Load
Aluminium
Copper
Zinc
None of the above
Q.23
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.24
A rotary converter operates at a
low power factor
high power factor
zero power factor
none of the above
Q.25
Which of the following is reversible in action?
Motor generator set
Motor converter
Rotary converter
Any of the above
E. None of the above
Q.26
Selenium rectifier can be operated at temperatures as high as
25°C
40°C
60°C
75°C
Q.27
The ionization potential of mercury is approximately
5.4 V
8.4 V
10.4 V
16.4 V
Q.28
A mercury arc rectifier possesses ________ regulation characteristics
straight line
curved line
exponential
none of the above
Q.29
In phase-shift control method the control is carried out by varying the of grid voltage.
magnitude
polarity
phase
any of the above
E. none of the above
Q.30
In which of the following appUcations, direct current is absolutely essential ?
Illumination
Electrolysis
Variable speed operation
Traction
0 h : 0 m : 1 s
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