Question is ⇒ D.C. series machine has field consisting of, Options are ⇒ (A) many number of turns of thick wire, (B) many number of turns of thin wire, (C) few number of turns of thick wire, (D) few number of turns of thin wire, (E) , Leave your comments or Download question paper.

Question is ⇒ D.C. series machine has field consisting of, Options are ⇒ (A) many number of turns of thick wire, (B) many number of turns of thin wire, (C) few number of turns of thick wire, (D) few number of turns of thin wire, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	D.C. series machine has field consisting of
A.	many number of turns of thick wire [Wrong Answer]
B.	many number of turns of thin wire [Wrong Answer]
C.	few number of turns of thick wire [Correct Answer]
D.	few number of turns of thin wire [Wrong Answer]
View Answer 6 -4 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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⇒ D.C. shunt motors are used for driving
trains
cranes
hoists
machine tools

⇒ In case of D.C. shunt motors the speed is dependent on back e.m.f. only because
back e.m.f. is equal to armature drop
armature drop is negligible
flux is proportional to armature current
flux is practically constant in ac. shunt motors

⇒ In case of conductively compensated D.C. series motors, the compensating winding is provided
as separately wound unit
in parallel with armature winding
in series with armature winding
in parallel with field winding

⇒ 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

⇒ Regenerative braking on D.C. shunt motors is used when
the load has overhauling characteristics
the load is variable
the load also acts as a braking force
the load is constantly decreasing

⇒ 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

⇒ 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

⇒ 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

⇒ 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 hysteresis loss in a D.C. generator varies with the frequency of magrietic reversals as
1/f
f
f^1.6
f²

⇒ As compared to an induction motor, the air gap in a D.C. motor is
less than 50%
between 50% and 90%
same
more

⇒ The mechanical power developed by a D.C. motor is equal to
power input + losses
back e.m.f. X armature current
power output X losses
power output X efficiency

⇒ The speed of a D.C. motor, under constant load conditions, is affected by
back e.m.f.
field flux
armature current
none of the above

⇒ 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

⇒ 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
Shunt motor with commutating pole
Compound motor without commutating poles

⇒ 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

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

⇒ Which of the following loss of D.C. motor decreases with increase in load ?
Friction and windage loss
Core loss
Brush contact loss
none of the above

⇒ What will happen if supply terminals of D.C. shunt motor are interchanged ?
The direction of rotation will reverse
Motor will stop
Motor will run at speed lower than the normal speed in the same direction
Motor will run at its normal speed in the same direction as it was running

⇒ 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

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

⇒ 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

⇒ Sparking at the commutator of a D.C. motor may result in
damage to commutator segments
damage to commutator insulation
increased power consumption
all of the above

⇒ 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

⇒ 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

⇒ 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

⇒ 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

⇒ The maximum end-play of a motor is about
10 mm
6 mm
2 mm
0.4 mm

⇒ 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

⇒ 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