Question is ⇒ In the D.C. motor the iron losses occur in, Options are ⇒ (A) the field, (B) the armature, (C) the brushes, (D) the commutator, (E) , Leave your comments or Download question paper.

Question is ⇒ In the D.C. motor the iron losses occur in, Options are ⇒ (A) the field, (B) the armature, (C) the brushes, (D) the commutator, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	In the D.C. motor the iron losses occur in
A.	the field [Wrong Answer]
B.	the armature [Correct Answer]
C.	the brushes [Wrong Answer]
D.	the commutator [Wrong Answer]
View Answer 8 -2 Explanation:- Answer : B Discuss it below : !! OOPS Login [Click here] is required to post your answer/result Help other students, write article, leave your comments

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⇒ D.C. generators are normally designed for maximum efficiency around
full-load
rated r.p.m.
rated voltage
all of the above

⇒ In a D.C. motor, the ratio Eb/Va indicates
running torque of the motor
starting torque of the motor
efficiency of the motor
speed regulation of the motor

⇒ The operation of electric generators and motors depend on the interaction between magnetic field and
copper conductors
electric field
electric current
commutator

⇒ As the load is increased the speed of D.C. shunt motor will
reduce slightly
increase slightly
increase proportionately -
remains unchanged

⇒ For which types of D.C. motor, dynamic braking is generally used ?
Shunt motors
Series motors
Compound motors
All of the above

⇒ In Ward-Leonard control the lower limit of speed is imposed by
residual magnetism of the generator
core losses of motor
mechanical losses of motor and generator together
all of the above

⇒ Which of the following is not necessarily the advantage of D.C. motors over A.C. motors ?
Better speed control
Low cost
High starting torque
Wide speed range

⇒ Which of the following motors is usually used in house-hold refrigerators ?
D.C. shunt motor
D.C. series motor
Single phase induction motor (split phase start or induction run motor)
Reluctance motor

⇒ If the field circuit of a loaded shunt motor is suddenly opened
torque developed by the motor would be reduced to zero
it would race to almost infinite speed
it would draw abnormally high armature current
the fuse or circuit breaker will open the circuit before too much damage is done to the motor

⇒ Which of the following D.C. motors has the least drop in speed between no-load and nominal load ?
Series motor without commutating poles
Series motor with commutating poles
Shunt motor with commutating pole
Compound motor without commutating poles

⇒ What will happen if supply terminals of D.C. shunt motor are interchanged ?
The direction of rotation will reverse
Motor will stop
Motor will run at speed lower than the normal speed in the same direction
Motor will run at its normal speed in the same direction as it was running

⇒ If conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be
less than 50%
60 to 70%
80 to 90%
1

⇒ A D.C. series motor is that which
has its field winding consisting of thick wire and less turns
has a poor torque
can be started easily without load
has almost constant speed

⇒ Differentially compound D.C. motors can find applications requiring
high starting torque
low starting torque
variable speed
frequent on-off cycles

⇒ The total losses in a well designed D.C. generator of 10 kW will be nearly
100 W
500 W
1000 W
1500 W

⇒ Field winding of a D.C. series motor is usually provided with thick wire
to provide large flux
to reduce the use of insulating materials
as it carries large load current
in order to reduce eddy current

⇒ Which loss in a D.C. generator varies with load ?
Copper loss
Eddy current loss
Hysteresis loss
Windage loss

⇒ Which of the following statement is incorrect ? If a starter is not used with large D.C. motor, it will draw a starting current which
will produce very low starting torque
will produce excessive line voltage drop
will damage the cOmmutator
is many times its full-load current

⇒ In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be
almost negligible
rated full-load current
less than full-load current
more than full-load current

⇒ Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control
drum type controller is used
three point starter is used
four point starter is used
all above can be used

⇒ If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor
of lower H.P. should be selected
of higher H.P. should be selected
can be used for 50°C ambient temperature also
is to be derated by a factor recommended by manufacturer and select the next higher H.P. motor

⇒ In a D.C. shunt motor, speed is
independent of armature current
directly proportional to the armature current
proportional to the square of the current
inversely proportional to the armature current

⇒ The main disadvantage of the Ward- Leonard control method is
high initial cost
high maintenance cost
low efficiency at light loads
all of the above

⇒ A D.C. series motor, as compared to shunt and compound motors, has the highest torque at the start because of its comparatively
stronger series field
lower armature resistance
large armature current
fewer series turns

⇒ Which method of braking is generally used in elevators ?
Plugging
Regenerative braking
Rheostatic braking
None of the above

⇒ In a D.C. motor constant torque is produced due to
rotor laminations
end-plates
pole shoes
commutator

⇒ Which of the following loss in a D.C. generator varies significantly with the load current ?
Field copper loss
Windage loss
Armature copper loss
None of the above

⇒ When the armature of a D.C. motor rotates, e.m.f. induced is
self-induced e.m.f.
mutually induced e.m.f.
back e.m.f.
none of the above

⇒ D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select this
series motor
shunt motor
compound motor
any of the above

⇒ Which of the following can be used for controlling the speed of a D.C. motor ?
Thermistor
Transistor
Thyratron
Thyristor