Question is ⇒ VVhat is the effect produced by the electric current in an electric motor ?, Options are ⇒ (A) Heating effect only, (B) Magnetic effect only, (C) Heating as well as magnetic effect, (D) Heating as well as chemical effect, (E) , Leave your comments or Download question paper.

Question is ⇒ VVhat is the effect produced by the electric current in an electric motor ?, Options are ⇒ (A) Heating effect only, (B) Magnetic effect only, (C) Heating as well as magnetic effect, (D) Heating as well as chemical effect, (E) , Leave your comments or Download question paper. Previous question Next question


Q1.	VVhat is the effect produced by the electric current in an electric motor ?
A.	Heating effect only [Wrong Answer]
B.	Magnetic effect only [Wrong Answer]
C.	Heating as well as magnetic effect [Correct Answer]
D.	Heating as well as chemical effect [Wrong Answer]
View Answer 3 -3 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. 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

⇒ If Ia be the armature current, then speed of a D.C. shunt motor is
independent of la
proportional to Ia
varies as (la)²
varies as¹/_{I_a}

⇒ The plugging gives the
zero torque braking
smallest torque braking
highest torque braking
none of the above

⇒ 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.

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

⇒ 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

⇒ In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be
almost negligible
rated full-load current
less than full-load current
more than full-load current

⇒ Hopkinson's test is conducted at
no load
part load
low load
full load

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

⇒ A face plate starter is employed for starting
induction motor
universal motor
synchronous motor
d.c. series motor

⇒ Starters are used with D.C. motors because
these motors have high starting torque
these motors are not self-starting
back e.m.f. of these motors is zero initially
to restrict armature current as there is no back e.m.f. while starting

⇒ 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

⇒ As there is no back e.m.f. at the instant of starting, a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit
a resistance is connected in series with armature
a resistance is connected parallel to the armature
armature is temporarily open circuited
a high value resistor is connected across the field winding

⇒ 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

⇒ 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

⇒ The current drawn by the armature of D.C. motor is directly proportional to
the torque required
the speed of the motor
the voltage across the terminals
none of the above

⇒ Three point starter can be used for
series motor only
shunt motor only
compound motor only
both shunt and compound motor

⇒ A D.C. motor can be easily identified by
winding
commutator
size of conductor
yoke

⇒ Which of the following tests will be suitable for testing two similar D.C. series motors of large capacity ?
Swinburne's test
Hopkinson's test
Field test
Brake test

⇒ 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

⇒ In D.C. machines fractional pitch winding is used
to improve cooling
to reduce copper losses
to increase the generated e.m.f.
to reduce the sparking

⇒ Which loss in a D.C. generator varies with load ?
Copper loss
Eddy current loss
Hysteresis loss
Windage loss

⇒ The speed of a D.C. motor can be varied by varying
field current
applied voltage
resistance in series with armature
any of the above

⇒ In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will
remain unchanged
reduce to one-fourth value
increase four folds
be doubled

⇒ In case of a shunt motor if the supply voltage is increased by 10%, which of the following will decrease ?
full load current
full load speed
starting torque
none of the above

⇒ Which of the following methods gives the greatest breaking torque ?
Regenerative braking
Plugging
Rheostatic braking
None 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 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

⇒ 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

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