Question is ⇒ Sparking is discouraged in a D.C. motor because, Options are ⇒ (A) it increases the input power consumption, (B) commutator gets damaged, (C) both (a) and (b), (D) none of the above, (E) , Leave your comments or Download question paper.

Question is ⇒ Sparking is discouraged in a D.C. motor because, Options are ⇒ (A) it increases the input power consumption, (B) commutator gets damaged, (C) both (a) and (b), (D) none of the above, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	Sparking is discouraged in a D.C. motor because
A.	it increases the input power consumption [Wrong Answer]
B.	commutator gets damaged [Correct Answer]
C.	both (a) and (b) [Wrong Answer]
D.	none of the above [Wrong Answer]
View Answer 7 -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 is preferred for elevators ?
Shunt motor
Series motor
Differential compoun.d motor
Cumulative compound motor

⇒ Regenerative method of braking is based on that
back e.m.f. is less than the applied voltage
back e.m.f. is equal to the applied voltage
back e.m.f. of rotor is more than the applied voltage
none of the above

⇒ 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

⇒ 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

⇒ When two D.C. series motors are connected in parallel, the resultant speed is
more than the normal speed
loss than the normal speed
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⇒ If Ia be the armature current, then speed of a D.C. shunt motor is
independent of la
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varies as (la)²
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⇒ Which of the following methods is most effective in finding out the no load losses in a large D.C. shunt motor ?
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⇒ Which of the following tests can be conducted on all types of D.C. machines ?
Hopkinson's test
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⇒ The use of armature divertor in the rheostatic method of speed control for a D.C. shunt motor makes the method
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less wasteful
suitable for rapidly changing loads
unsuitable for changing loads

⇒ Which of the following methods of braking is used in rolling mills ?
Dynamic braking
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elevators
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colliery winders

⇒ 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

⇒ In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to
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50% of the previous value
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⇒ If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor
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of higher H.P. should be selected
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⇒ According to Fleming's left hand rule, when the forefinger points in the direction of the field or flux, the middle finger will point in the direction of
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movement of conductor
resultant force on conductor
none of the above

⇒ The armature torque of the D.C. shunt motor is proportional to
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armature current only
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⇒ The maximum end-play of a motor is about
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6 mm
2 mm
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⇒ D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select this
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(B_max)^2.4

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Series motor
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increasing the resistance in field circuit
reducing the resistance in the field circuit
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⇒ Which of the following motors, on removal of load, will run at the highest speed ?
Shunt motor
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⇒ Which loss in a D.C. generator varies with load ?
Copper loss
Eddy current loss
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