Question is ⇒ In case the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be, Options are ⇒ (A) 1, (B) around 90%, (C) anywhere between 75% and 90%, (D) less than 50%, (E) , Leave your comments or Download question paper.

Question is ⇒ In case the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be, Options are ⇒ (A) 1, (B) around 90%, (C) anywhere between 75% and 90%, (D) less than 50%, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	In case the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be
A.	1 [Wrong Answer]
B.	around 90% [Wrong Answer]
C.	anywhere between 75% and 90% [Wrong Answer]
D.	less than 50% [Correct Answer]
View Answer 3 -2 Explanation:- Answer : D 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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Also Read Similar Questions Below :

⇒ Which of the following steps is likely to result in reduction of hysteresis loss in a D.C. generator ?
Providing laminations in armature core
Providing laminations in stator
Using non-magnetic material for frame
Using material of low hysteresis coefficient for armature core material

⇒ The plugging gives the
zero torque braking
smallest torque braking
highest torque braking
none of the above

⇒ 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

⇒ D.C. generators are installed near the load centres to reduce
iron losses
line losses
sparking
corona losses

⇒ 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
Separately excited motor

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

⇒ In hazardous area of gassy mines, material transportation is done by vehicles powered by
A.C. mains
D.C. mains
I.C. engines
batteries

⇒ 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

⇒ In a D.C. motor if the back e.m.f. is absent
motor will burn
motor will not run at all
motor will run at very slow speed
motor will run at very high speed

⇒ 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%

⇒ 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

⇒ Which of the following losses are significantly reduced by laminating the core of a D.C. generator ?
Hysteresis losses
Eddy current losses
Copper losses
Windage losses

⇒ D.C. series machine has field consisting of
many number of turns of thick wire
many number of turns of thin wire
few number of turns of thick wire
few number of turns of thin wire

⇒ 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 resistance is connected in series with armature
a resistance is connected parallel to the armature
armature is temporarily open circuited
a high value resistor is connected across the field winding

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

⇒ The armature voltage control of D.C. motor provides
constant voltage drive
constant current drive
constant torque drive
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

⇒ A shearing machine has cyclic load consisting of intermittent light and henry loads. Which of the following D.C. motor will be suitable for this purpose?
Series motor
Shunt motor
Cumulative compound motor
Differential compound motor

⇒ All motors, basically, operate on the principie of either repulsion or
induction
semi-conduction
capacitance
electro-magnetism

⇒ In variable speed motor
a stronger commutating field is needed at low speed than at high speed
a weaker commutating field is needed at low speed than at higt speed
same commutating field is needed at low speed than at high speed
none of the above is correct

⇒ The speed of a D.C. shunt motor more than its full-load speed can be obtained by
decreasing the field current
increasing the field current
decreasing the armature current
increasing the armature current

⇒ When two D.C. series motors are connected in parallel, the resultant speed is
more than the normal speed
loss than the normal speed
normal speed
zero

⇒ 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

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

⇒ 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

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

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

⇒ Which of the following motor has the poorest speed regulation ?
Shunt motor
Series motor
Differential compound motor
Cumulative compound motor

⇒ Which of the following methods is most effective in finding out the no load losses in a large D.C. shunt motor ?
Field's test
Ward-Leonard test
Block rotor test
Swinburne's test

⇒ If the field of a D.C. shunt motor gets opened while motor is running
the speed of motor will be reduced
the armature current will reduce
the motor will attain dangerously high speed
the motor will continue to run at constant speed