EE&I QUIZ
The basic function of a transformer is to change
A
the level of the voltage.
B
the power level.
C
the power factor.
D
the frequency.
Transformer is used
A
to step up the voltage.
B
to step down the voltage
C
on dc.
D
to step up or step down the voltage.
An auto-transformer has
A
one winding with taps taken out
B
two interlaced windings.
C
two windings of same wire.
D
two windings of different materials.
E
one winding without taps.
The efficiency of a power transformer is around
A
50%
B
60%
C
80%
D
95%
Transformer action requires a
A
constant magnetic flux.
B
increasing magnetic flux.
C
alternating magnetic flux.
D
alternating electric flux.
In a transformer operating at constant voltage,
if the input frequency increases, the core loss
A
increases.
B
decreases
C
remains constant.
D
increases as square of the frequency
The wattage rating for a ceiling motor will be in
the range
A
50 to 250W.
B
250 to 500W.
C
50 to 150W.
D
10 to 20W
If a dc series motor is operated on ac supply, it
A
will not start at all
B
will start and run but will have poor
performance such as excessive sparking,
poor efficiency and poor power factor
C
will get damaged due to burning of its
windings.
D
will run at excessively high speed.
A distribution transformer is selected on the
basis of
A
voltage regulation.
B
efficiency.
C
all day efficiency.
D
none of these.
The function of oil in a transformer is
A
to provide insulation and cooling.
B
to provide protection against lightning.
C
to provide protection against short-circuit.
D
to provide lubrication.
Torque development in a dc motor depends on:
A
Magnetic field and radius of armature
B
Current flowing through the armature
conductors
C
Active length of the conductors and
number of armature conductors
D
All the above
A dc motor having full load speed of 750 rpm
and speed regulation of 10% will have no load
speed of:
A
825 rpm
B
675 rpm
C
800 rpm
D
700 rpm
A DC shunt motor is running at light load, what
happens if the field winding gets opened?
A
Motor will stop
B
Motor will burn
C
Motor will make noise
D
Motor will pickup high speed
In an electrical motor, the electromagnetic torque
developed is:
A
In opposite direction to both load torque and
fractional torque
B
In the same direction to the load torque but
opposite direction to the fractional torque
C
In the same direction as the load torque and
fractional torque
D
In the same direction as the fractional torque
but in opposite direction to the load torque
The starting torque of dc shunt motor is:
A
Zero
B
Low
C
High
D
Very high
A DC shunt motor may have rising speed-torque
characteristics due to:
A
Very high armature circuit resistance
B
Very high field circuit resistance
C
Very high demagnetizing armature
resistance
D
Very low demagnetizing armature reaction
The dc motor, that has poorest speed regulation
is
A
Cumulative compound
B
Differential compound
C
Series
D
Shunt
If the supply voltage to a dc shunt motor is
increased by 15%, which of the following will
reduce?
A
Full load current
B
Full load speed
C
Starting torque
D
None of the above
The speed of dc shunt motor can be increased
above its normal speed by:
A
Increasing the field current
B
Decreasing the field current
C
Decreasing the terminal voltage
D
Increasing the armature resistance
By looking at which part of the motor, it can be
easily confirmed that a particular motor is
D.C. motor?
A
Frame
B
Shaft
C
Commutator
D
Stator
A D.C. series motor is that which
A
has its field winding consisting of thick
wire and less turns
B
has a poor torque
C
can be started easily without load
D
has almost constant speed
When two D.C. series motors are connected in
parallel, the resultant speed is
A
more than the normal speed
B
loss than the normal speed
C
normal speed
D
zero
If a D.C. motor is to be selected for conveyors,
which motor would be preferred ?
A
Series motor
B
Shunt motor
C
Differentially compound motor
D
Cumulative compound motor
Which D.C. motor is preferred for elevators ?
A Shunt motor
B Series motor
C Differential compound motor
D Cumulative compound motor
What will happen if the back e.m.f. of a D.C.
motor vanishes suddenly?
A The motor will stop
B The motor will continue to run
C The armature may burn
D The motor will run noisy