Question is ⇒ As compared to an induction motor, the air gap in a D.C. motor is, Options are ⇒ (A) less than 50%, (B) between 50% and 90%, (C) same, (D) more, (E) , Leave your comments or Download question paper.

Question is ⇒ As compared to an induction motor, the air gap in a D.C. motor is, Options are ⇒ (A) less than 50%, (B) between 50% and 90%, (C) same, (D) more, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	As compared to an induction motor, the air gap in a D.C. motor is
A.	less than 50% [Wrong Answer]
B.	between 50% and 90% [Wrong Answer]
C.	same [Wrong Answer]
D.	more [Correct Answer]
View Answer 13 -9 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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⇒ The purpose of retardation test on D.C. shunt machines is to find out
stray losses
eddy current losses
field copper losses
windage losses

⇒ The condition for maximum power in case of D.C. motor is
back e.m.f. = 2 x supply voltage
back e.m.f. = 1/2 x supply voltage
supply voltage = 1/2 x back e.m.f.
supply voltage = back e.m.f.

⇒ The series parallel system of speed control of D.C. series motors widely used in traction work gives a speed range of about
1 : 10
1 : 8
1 : 6
1 : 4

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

⇒ What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?
The motor will stop
The motor will continue to run
The armature may burn
The motor will run noisy

⇒ 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

⇒ At the instant of starting when a D.C. motor is put on supply, it behaves like
a highly resistive circuit
a low resistance circuit
a capacitive circuit
none of the above

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

⇒ 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

⇒ 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 main disadvantage of Hopkinson's test for finding efficiency of the shunt D.C. motors is that it
needs one motor and one generator
requires two identical shunt machines
requires full-load power
ignores any change in iron loss

⇒ Which motor should be used for centrifugal pumps ?
Series motor
Shunt motor
Either of the above
None of the above

⇒ Which of the following loss in a D.C. generator is dissipated in the form of heat ?
Mechanical loss
Core loss
Copper loss
All of the above

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

⇒ In a differentially compounded D.C. motor, if shunt field suddenly opens
the motor will first stop and then run in opposite direction as series motor
the motor will work as series motor and run at slow speed in the same direction
the motor will work as series motor and run at high speed in the same direction
the motor will not work and come to stop

⇒ VVhat is the effect produced by the electric current in an electric motor ?
Heating effect only
Magnetic effect only
Heating as well as magnetic effect
Heating as well as chemical effect

⇒ 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

⇒ 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

⇒ 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

⇒ Hopkinson's test is conducted at
no load
part load
low load
full 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

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

⇒ The condition for maximum efficiency for a D.C. generator is
eddy current losses = stray losses
hysteresis losses = eddy current losses
copper losses = 0
variable losses = constant losses

⇒ The speed of a D.C. shunt motor is required to be more than full load speed. This is possible by
reducing the field current
decreasing the armature current
increasing the armature current
increasing the excitation current

⇒ The rated speed of a given D.C. shunt motor is 900 r.p.m. To run this machine at 1000 r.p.m., which of the following speed control scheme will be used ?
Ward-leonard control
Armature current resistance control
Field resistance control
None of the above

⇒ Hopkinson's test on D.C. machines is conducted at
no-load
part load
full-load
overload

⇒ During rheostat braking of D.C. series motors
motor is run as a generator
motor is reversed in direction
motor is run at reduced speed

⇒ In Ward Leonard method of speed control of a D.C. motor, change in speed of motor is obtained by the
change in armature voltage of D.C. motor
change in the field excitation of the D.C. motor
change in armature current of D.C. motor
change in supply voltage

⇒ 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

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