Question is ⇒ A D.C. motor can be easily identified by, Options are ⇒ (A) winding, (B) commutator, (C) size of conductor, (D) yoke, (E) , Leave your comments or Download question paper.

Question is ⇒ A D.C. motor can be easily identified by, Options are ⇒ (A) winding, (B) commutator, (C) size of conductor, (D) yoke, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	A D.C. motor can be easily identified by
A.	winding [Wrong Answer]
B.	commutator [Correct Answer]
C.	size of conductor [Wrong Answer]
D.	yoke [Wrong Answer]
View Answer 22 -14 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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⇒ The plugging gives the
zero torque braking
smallest torque braking
highest torque braking
none of the above

⇒ In a D.C. generator all of the following could be the effects of iron losses except
Loss of efficiency
Excessive heating of core
Increase in terminal voltage
Rise in temperature of ventilating air

⇒ In which of the following applications D.C. series motor is invariably tried?
Starter for a car
Drive for a water pump
Fan motor
Motor operation in A.C. or D.C.

⇒ A wide and very sensitive speed control is usually required in case of
elevators
steel rolling mills
colliery winders
all of the above

⇒ In case the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be
1
around 90%
anywhere between 75% and 90%
less than 50%

⇒ Which loss in a D.C. generator does not vary with load as well as flux density ?
Copper loss
Eddy current loss
Hysteresis loss
Windage loss

⇒ 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

⇒ 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

⇒ Speed control by Ward Leonard method gives uniform speed variation
in one direction
in both directions
below normal speed only
above normal speed only

⇒ Which D.C. motor has got maximum self relieving property ?
Series motor
Shunt motor
Cumulatively compounded motor
Differentially compounded 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

⇒ Starters are used with D.C. motors because
these motors have high starting torque
these motors are not self-starting
back e.m.f. of these motors is zero initially
to restrict armature current as there is no back e.m.f. while starting

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

⇒ In a manual shunt motor starter
over load relay is connected in series and no volt relay in parallel with the load
over load relay is connected in parallel and no volt relay in series with the load
over load relay and no volt relay are both connected in series with the load
over load relay and no volt relay are both connected in parallel with the load

⇒ The current drawn by the armature of D.C. motor is directly proportional to
the torque required
the speed of the motor
the voltage across the terminals
none of the above

⇒ A series motor is' best suited for driving
machine tools
cranes and hoists
shear and punches
none of the above

⇒ Between Field's test and Hopkinson's test the main common thing is that both
use negligible power
are regenerative tests
need two similar mechanicallycoupled motors
need two electrically coupled series motors

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

⇒ For which application a D.C. motor is preferred over an A.C. motor ?
High speed operation
Low speed operation
Fixed speed operation
Variable speed operation

⇒ Torque developed by a D.C. motor depends upon
active length of the conductor
current flow through the conductors
number of conductors
radius of armature

⇒ Following motor is used where high starting torque and wide speed range control is required.
Single phase capacitor start
Induction motor
Synchronous motor
D.C. motor

⇒ Which of the following motor is preferred for operation in highly explosive atmosphere ?
Series motor
Shunt motor
Air motor
Battery operated motor

⇒ Sparking is discouraged in a D.C. motor because
it increases the input power consumption
commutator gets damaged
both (a) and (b)
none of the above

⇒ 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 losses can be determined by performing the retardation test ?
Friction losses
Eddy current losses
Stray losses
Copper losses

⇒ The speed of a D.C. shunt motor can be increased by
increasing the resistance in armature circuit
increasing the resistance in field circuit
reducing the resistance in the field circuit
reducing the resistance in the armature circuit

⇒ The starting resistance of a D.C. motor is generally
low
around 500 ohms
1000 ohms
infinitely large

⇒ 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

⇒ The speed regulation of a D.C. motor is

lowest speed

highest speed

highest speed - lowest speed

average speed

no-load speed - full-load speed

full-load speed

no-load speed - full-load speed

no-load speed

⇒ A series motor is started without load. The effect is that
the back e.m.f. decreases
the torque increases rapidly
the speed increases rapidly
the current drawn increases rapidly