Question is ⇒ The generated e.m.f. and the current are in the opposite direction in case of, Options are ⇒ (A) d.c. generators, (B) d.c. motors, (C) both (a) and (b), (D) none of the above, (E) , Leave your comments or Download question paper.

Question is ⇒ The generated e.m.f. and the current are in the opposite direction in case of, Options are ⇒ (A) d.c. generators, (B) d.c. motors, (C) both (a) and (b), (D) none of the above, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	The generated e.m.f. and the current are in the opposite direction in case of
A.	d.c. generators [Wrong Answer]
B.	d.c. motors [Correct Answer]
C.	both (a) and (b) [Wrong Answer]
D.	none of the above [Wrong Answer]
View Answer 5 -7 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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⇒ Which D.C. motor will be preferred for machine tools ?
Series motor
Shunt motor
Cumulative compound motor
Differential compound motor

⇒ 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

⇒ 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

⇒ Which of the following motor has high starting torque ?
Synchronous motor
A.C. series motor
D.C. series motor
Induction motor

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

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

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

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

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shunt
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any unbalanced magnetic pull on the armature core
twisting strains due to transmission of torque
bending moment due to the weight of the armature and commutator
all of the above

⇒ Which of the following methods is most ecoriomical fol. finding the no-load losses of a large b.C. shunt motor ?
Retardation test
Swinburne's test
Hopkinson's test
none of the above

⇒ 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

⇒ 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

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

⇒ If a D.C. motor is to be selected for conveyors, which motor would be preferred ?
Series motor
Shunt motor
Differentially compound motor
Cumulative compound motor

⇒ 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

⇒ In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to
100% of the previous value
50% of the previous value
25% of the previous value
10% of the previous value

⇒ 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

⇒ 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

⇒ The generated e.m.f. and the current are in the opposite direction in case of
d.c. generators
d.c. motors
both (a) and (b)
none of the above

⇒ As compared to an induction motor, the air gap in a D.C. motor is
less than 50%
between 50% and 90%
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⇒ 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 statement is incorrect ? If a starter is not used with large D.C. motor, it will draw a starting current which
will produce very low starting torque
will produce excessive line voltage drop
will damage the cOmmutator
is many times its full-load current

⇒ 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

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6 mm
2 mm
0.4 mm

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series motors
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compound motors
none of the above

⇒ If conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be
less than 50%
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