Question is ⇒ If Ta be the torque and Ia the armature current for a D.C. motor, then which of the following relation is valid before saturation ?, Options are ⇒ (A) Ta ∝ Ia, (B) Ta ∝ I/Ia, (C) Ta ∝ Ia2, (D) Ta ∝ I/Ia2, (E) , Leave your comments or Download question paper.

Question is ⇒ If Ta be the torque and Ia the armature current for a D.C. motor, then which of the following relation is valid before saturation ?, Options are ⇒ (A) Ta ∝ Ia, (B) Ta ∝ I/Ia, (C) Ta ∝ Ia2, (D) Ta ∝ I/Ia2, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	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 ?
A.	T_a ∝ I_a [Wrong Answer]
B.	T_a ∝ I/I_a [Wrong Answer]
C.	T_a ∝ I_a² [Correct Answer]
D.	T_a ∝ ^I/_{I_a²} [Wrong Answer]
View Answer 7 -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

Previous question Next question

Also Read Similar Questions Below :

⇒ The armature shaft of a D.C. motor must be able to withstand
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

⇒ 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

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

⇒ Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be
level compounded
under compounded
cumulatively compounded
differentially compounded

⇒ If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will
increase
decrease
remain same
become zero

⇒ 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

⇒ 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}

⇒ If t be the thickness of the laminations, then eddy current loss in a generator. will vary as
¹/_t
¹/_t²
t
t²

⇒ A brake test on D.C. motors is usually restricted to
small horse power motors
variable speed motors
high speed motors
open frame type motors.

⇒ A wide and very sensitive speed control is usually required in case of
elevators
steel rolling mills
colliery winders
all of the above

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

⇒ Which of the following methods of braking is used in rolling mills ?
Dynamic braking
Plugging
Regenerative braking
Mechanical brakes

⇒ 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 main disadvantage of the Ward- Leonard control method is
high initial cost
high maintenance cost
low efficiency at light loads
all of the above

⇒ Which one of the following is not the function of pole shoes in a D.C. machine ?
To reduce eddy current loss
To support the field coils
To spread out flux for better uniformity
To reduce the reluctance of the magnetic path

⇒ If the terminals of armature of D.C. motor are interchanged, this action will offer following kind of braking
regenerative
plugging
dynamic braking
none of the above

⇒ 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 losses occurring in a D.C. generator are given below. Which loss is likely to have highest proportion at rated load of the generator ?
hysteresis loss
field copper loss
armature copper loss
eddy current loss

⇒ 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

⇒ If the supply voltage for a D.C. motor is increased, which of the following will decrease ?
Starting torque
Operating speed
Full-load current
All of the above

⇒ To get the speed of D.C. motor below the normal without wastage of electrical energy ____ is used.
Ward Leonard control
rheostatic control
any of the above method
none of the above method

⇒ In hazardous area of gassy mines, material transportation is done by vehicles powered by
A.C. mains
D.C. mains
I.C. engines
batteries

⇒ 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

⇒ In the D.C. motor the iron losses occur in
the field
the armature
the brushes
the commutator

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

⇒ 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

⇒ 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

⇒ In an overloaded motor main danger arises due to
winding getting overheated
busbars getting heated
starter getting damaged
bearings getting overheated

⇒ For constant torque drive which speed control method is preferred ?
Field control
Armature voltage control
Shunt armature control
Mechanical loading system

⇒ In case the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be
1
around 90%
anywhere between 75% and 90%
less than 50%