Question is ⇒ The losses occurring in a D.C. generator are given below. Which loss is likely to have the least proportion ?, Options are ⇒ (A) Magnetic losses, (B) Armature copper losses, (C) Mechanical losses, (D) Field copper losses, (E) , Leave your comments or Download question paper.

Question is ⇒ The losses occurring in a D.C. generator are given below. Which loss is likely to have the least proportion ?, Options are ⇒ (A) Magnetic losses, (B) Armature copper losses, (C) Mechanical losses, (D) Field copper losses, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	The losses occurring in a D.C. generator are given below. Which loss is likely to have the least proportion ?
A.	Magnetic losses [Wrong Answer]
B.	Armature copper losses [Wrong Answer]
C.	Mechanical losses [Correct Answer]
D.	Field copper losses [Wrong Answer]
View Answer 5 -1 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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⇒ The speed of a D.C. series motor is
proportional to the armature current
proportional to the square of the armature current
proportional to field current
inversely proportional to the armature current

⇒ 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

⇒ In a D.C. generator all of the following could be the effects of iron losses except
Loss of efficiency
Excessive heating of core
Increase in terminal voltage
Rise in temperature of ventilating air

⇒ 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

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

⇒ For the same H.P. rating and full load speed, following motor has poor starting torque
shunt
series
differentially compounded
cumulatively compounded

⇒ Which losses can be determined by performing the retardation test ?
Friction losses
Eddy current losses
Stray losses
Copper losses

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

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

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

⇒ The use of armature divertor in the rheostatic method of speed control for a D.C. shunt motor makes the method
less expensive
less wasteful
suitable for rapidly changing loads
unsuitable for changing loads

⇒ The main disadvantage of Hopkinson's test for finding efficiency of the shunt D.C. motors is that it
needs one motor and one generator
requires two identical shunt machines
requires full-load power
ignores any change in iron loss

⇒ Why are the D.C. motors preferred for traction applications ?
Torque and speed are inversely proportional to armature current
Torque is proportional to armature current
Torque is proportional to square root of armature current
The speed is inversely proportional to the torque and the torque is proportional to square of armature current

⇒ Which of the following can be used for controlling the speed of a D.C. motor ?
Thermistor
Transistor
Thyratron
Thyristor

⇒ In variable speed motor
a stronger commutating field is needed at low speed than at high speed
a weaker commutating field is needed at low speed than at higt speed
same commutating field is needed at low speed than at high speed
none of the above is correct

⇒ If the no-voltage release of a D.C. motor starter fails to work on resumption of supply after a break, the motor will
not start automatically
start automatically without trouble
get damaged
develop very low torque

⇒ The speed of a series motor at no load is
infinity
4000 r.p.m.
2000 r.p.m.
1000 r.p.m.

⇒ Hopkinson's test on D.C. machines is conducted at
no-load
part load
full-load
overload

⇒ 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

⇒ The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. The speed regulation of the motor is
0.0236
0.0476
0.0677
0.0884

⇒ 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

⇒ 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

⇒ In D.C. machines the residual magnetism is of the order of
2 to 3 per cent
10 to 15 per cent -
20 to 25 per cent
50 to 75 per cent

⇒ Which of the following motors one will choose to drive the rotary compressor ?
D.C. shunt motor
D.C. series motor
Universal motor
Synchronous motor

⇒ The simplest form of a motor controller is
relay
toggle switch
drum switch
magnetic switch

⇒ A direct on line starter is used for starting motors
up to 5 H.P.
up to 10 H.P.
up to 15 H.P.
up to 20 H.P.

⇒ If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens
this will make armature to take heavy current, possibly burning it
this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
nothing will happen to motor
motor will come to stop

⇒ The series parallel system of speed control of D.C. series motors widely used in traction work gives a speed range of about
1 : 10
1 : 8
1 : 6
1 : 4

⇒ 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