Question is ⇒ As there is no back e.m.f. at the instant of starting, a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit, Options are ⇒ (A) a resistance is connected in series with armature, (B) a resistance is connected parallel to the armature, (C) armature is temporarily open circuited, (D) a high value resistor is connected across the field winding, (E) , Leave your comments or Download question paper.

Question is ⇒ As there is no back e.m.f. at the instant of starting, a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit, Options are ⇒ (A) a resistance is connected in series with armature, (B) a resistance is connected parallel to the armature, (C) armature is temporarily open circuited, (D) a high value resistor is connected across the field winding, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	As there is no back e.m.f. at the instant of starting, a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit
A.	a resistance is connected in series with armature [Correct Answer]
B.	a resistance is connected parallel to the armature [Wrong Answer]
C.	armature is temporarily open circuited [Wrong Answer]
D.	a high value resistor is connected across the field winding [Wrong Answer]
View Answer 5 -3 Explanation:- Answer : A 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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⇒ 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

⇒ 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

⇒ The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is
4.0
2.0
1.0
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⇒ If the supply voltage for a D.C. motor is increased, which of the following will decrease ?
Starting torque
Operating speed
Full-load current
All of the above

⇒ 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 Will have least percentage increase of input current for the same percentage increase in the torque?
Shunt motor
Series motor
Cumulative compound motor
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⇒ In case of conductively compensated D.C. series motors, the compensating winding is provided
as separately wound unit
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in series with armature winding
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⇒ The speed of a D.C. motor can be varied by varying
field current
applied voltage
resistance in series with armature
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⇒ Speed ,control by varying the armature circuit resistance, in a D.C. motor, provides a
constant torque drive
variable torque drive
constant power drive
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⇒ 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

⇒ A D.C. shunt motor is rotating in clockwise direction as viewed from one end. The polarity of connection of the armature and field winding are reversed simultaneously. The motor will
rotate in clockwise direction
rotate in anti-clockwise direction
will not rotate at all
gain excessively high speed

⇒ These days D.C. motors are widely used in
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air compressors
electric traction
machine shops

⇒ Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be
level compounded
under compounded
cumulatively compounded
differentially compounded

⇒ A 230 V D.C. shlint motor takes 32 A at full load. The back e.m.f. on full load, if the resistance of motor armature and shunt field windings are 0.2 Ω and 115 Ω respectively, will be
210 V
215 V
220 V
224 V

⇒ 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

⇒ If a D.C. motor is connected across the A.C. supply it will
run at normal speed
not run
run at lower Speed
burn due to heat produced in the field winding by eddy currents

⇒ The function of a field regulator for compound motors is to
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limit the armature current
demagnetise the field partially
none of the above

⇒ The use of armature divertor in the rheostatic method of speed control for a D.C. shunt motor makes the method
less expensive
less wasteful
suitable for rapidly changing loads
unsuitable for changing loads

⇒ Which D.C. motor will be preferred for machine tools ?
Series motor
Shunt motor
Cumulative compound motor
Differential compound motor

⇒ The armature torque of the D.C. shunt motor is proportional to
field flux only
armature current only
both (a) and (b)
none 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

⇒ If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens
nothing will happen to the motor
this will make armature to take heavy current, possibly burning it
this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
motor will run at very slow speed

⇒ In Field's test for series motors one motor drives the other machine as
cumulative compound generator
differential compound generator
separately excited generator
series generator

⇒ Which of the following, in a D.C. motor, can sustain the maximum temperature rise ?
Commutator
Armature windings
Slip rings
Field windings

⇒ Regenerative braking on shunt motors is used when
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the load is constantly decreasing
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the load has overhauling characteristics.

⇒ Which of the following motors one will choose to drive the rotary compressor ?
D.C. shunt motor
D.C. series motor
Universal motor
Synchronous motor

⇒ The armature voltage control of D.C. motor provides
constant torque drive
constant voltage drive
constant current drive
none of the above

⇒ The power mentioned on the name plate of an electric motor indicates
the power drawn in kW
the power drawn in kVA
the gross power
the output power available at the shaft

⇒ For starting a D.C. motor a starter is required because
it limits the speed of the motor
it limits the starting current to a safe value
it starts the motor
none of the above

⇒ No-load speed of which of the following motor will be highest ?
Shunt motor
Series motor
Cumulative compound motor
Differentiate compound motor