Question is ⇒ Field winding of a D.C. series motor is usually provided with thick wire, Options are ⇒ (A) to provide large flux, (B) to reduce the use of insulating materials, (C) as it carries large load current, (D) in order to reduce eddy current, (E) , Leave your comments or Download question paper.

Question is ⇒ Field winding of a D.C. series motor is usually provided with thick wire, Options are ⇒ (A) to provide large flux, (B) to reduce the use of insulating materials, (C) as it carries large load current, (D) in order to reduce eddy current, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	Field winding of a D.C. series motor is usually provided with thick wire
A.	to provide large flux [Wrong Answer]
B.	to reduce the use of insulating materials [Wrong Answer]
C.	as it carries large load current [Correct Answer]
D.	in order to reduce eddy current [Wrong Answer]
View Answer 10 -5 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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⇒ Which of the following can be used for controlling the speed of a D.C. motor ?
Thermistor
Transistor
Thyratron
Thyristor

⇒ Which of the following motor has the poorest speed regulation ?
Shunt motor
Series motor
Differential compound motor
Cumulative compound motor

⇒ 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

⇒ D.C. series motors are used
where load is constant
where load changes frequently
where constant operating speed is needed
in none of the above situations.

⇒ Ward-Leonard system of speed control is not recommended for
very low speeds
frequent motor reversals
wide speed range
constant speed operation

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

⇒ When the speed of a D.C. motor increases
back e.m.f. increases and current drawn decreases
back e.m.f. as well as current drawn both increase
back e.m.f. as well as current drawn both decrease
back e.m.f. decreases and current drawn increases

⇒ 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

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

⇒ The operation of electric generators and motors depend on the interaction between magnetic field and
copper conductors
electric field
electric current
commutator

⇒ 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
current, in the conductor
movement of conductor
resultant force on conductor
none of the above

⇒ 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

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

⇒ When the armature of a D.C. motor rotates, e.m.f. induced is
self-induced e.m.f.
mutually induced e.m.f.
back e.m.f.
none of the above

⇒ A shearing machine has cyclic load consisting of intermittent light and henry loads. Which of the following D.C. motor will be suitable for this purpose?
Series motor
Shunt motor
Cumulative compound motor
Differential compound motor

⇒ The speed of a D.C. shunt motor can be increased by
increasing the resistance in armature circuit
increasing the resistance in field circuit
reducing the resistance in the field circuit
reducing the resistance in the armature circuit

⇒ Which of the following motors is usually used in house-hold refrigerators ?
D.C. shunt motor
D.C. series motor
Single phase induction motor (split phase start or induction run motor)
Reluctance motor

⇒ 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

⇒ The condition for maximum efficiency for a D.C. generator is
eddy current losses = stray losses
hysteresis losses = eddy current losses
copper losses = 0
variable losses = constant losses

⇒ Between Field's test and Hopkinson's test the main common thing is that both
use negligible power
are regenerative tests
need two similar mechanicallycoupled motors
need two electrically coupled series motors

⇒ The condition for maximum power in case of D.C. motor is
back e.m.f. = 2 x supply voltage
back e.m.f. = 1/2 x supply voltage
supply voltage = 1/2 x back e.m.f.
supply voltage = back e.m.f.

⇒ Which of the following is not necessarily the advantage of D.C. motors over A.C. motors ?
Better speed control
Low cost
High starting torque
Wide speed range

⇒ 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

⇒ 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
series motor
shunt motor
compound motor
any of the above

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

⇒ For starting a D.C. motor a starter is required because
it limits the speed of the motor
it limits the starting current to a safe value
it starts the motor
none of the above

⇒ D.C. series machine has field consisting of
many number of turns of thick wire
many number of turns of thin wire
few number of turns of thick wire
few number of turns of thin wire

⇒ In a differentially compounded D.C. motor, if shunt field suddenly opens
the motor will first stop and then run in opposite direction as series motor
the motor will work as series motor and run at slow speed in the same direction
the motor will work as series motor and run at high speed in the same direction
the motor will not work and come to stop

⇒ D.C. shunt motors are used for driving
trains
cranes
hoists
machine tools

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