Question is ⇒ The operation of electric generators and motors depend on the interaction between magnetic field and, Options are ⇒ (A) copper conductors, (B) electric field, (C) electric current, (D) commutator, (E) , Leave your comments or Download question paper.

Question is ⇒ The operation of electric generators and motors depend on the interaction between magnetic field and, Options are ⇒ (A) copper conductors, (B) electric field, (C) electric current, (D) commutator, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	The operation of electric generators and motors depend on the interaction between magnetic field and
A.	copper conductors [Wrong Answer]
B.	electric field [Wrong Answer]
C.	electric current [Correct Answer]
D.	commutator [Wrong Answer]
View Answer 16 -10 Explanation:- Answer : C 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

⇒ Speed control by the variation of flux, in a D.C. shunt motor, will give
constant torque drive
variable torque drive
constant power drive
variable power drive

⇒ A three point starter is considered suitable for
shunt motors
shunt as well as compound motors
shunt, compound and series motors
all D.C. motors

⇒ Four point starter in the D.C. motor is used
to decrease the field current
to increase the field current
not to effect the current passing through Hold on coil even if any change M the field current takes place
all of the above

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

⇒ 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 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
0.5

⇒ 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

⇒ While starting a differential compound motor, it is best to short the series field in order to avoid
excessive starting period
motor starting in wrong direction
tripping of the circuit breaker
large in rush of current

⇒ 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

⇒ Which of the following law/rule can he used to determine the direction of rotation of D.C. motor ?
Lenz's law
Faraday's law
Coloumb's law
Fleming's left-hand rule

⇒ Which of the following motors have almost constant speed over their full load range ?
A.C. series motors
D.C. series motors
D.C. shunt motors
Low resistance squirrel cage motors

⇒ During rheostatic braking the braking torque is proportional to
speed
(speed)²
(speed)^-1
(speed)^-2

⇒ Small D.C. motors up to 5 H.P. usually have
2 poles
4 poles
6 poles
8 poles

⇒ The ratio of starting torque to fullload torque is least in case of
series motors
shunt motors
compound motors
none of the above

⇒ 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

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

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

⇒ D.C. series motors are used
where load is constant
where load changes frequently
where constant operating speed is needed
in none of the above situations.

⇒ 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

⇒ 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

⇒ If T_a be the torque and Ia the armature current for a D.C. motor, then which of the following relation is valid before saturation ?
T_a ∝ I_a
T_a ∝ I/I_a
T_a ∝ I_a²
T_a ∝ ^I/_{I_a²}

⇒ Which of the following motors, on removal of load, will run at the highest speed ?
Shunt motor
Series motor
Differential compound
Cumulative compound

⇒ Buses, trains, trolleys, hoists, cranes require high starting torque and therefore make use of
D.C. series motor
D.C. shunt motor
induction motor
all of above motors

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the load is variable
the load also acts as a braking force
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⇒ In D.C. machines fractional pitch winding is used
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to reduce copper losses
to increase the generated e.m.f.
to reduce the sparking

⇒ Which of the following method of speed control, of D.C. machine will offer minimum efficiency ?
Voltage control method
Field control method
Armature control method
All above methods

⇒ 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

⇒ One D.C. motor drives another D.C. motor. The second D.C. motor when excited and driven
runs as a generator
does not run as a generator
also runs as a motor
comes to stop after sometime

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