Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be
Q.3.
When the speed of D.C motor is increased
Back E.M.F increases and current drawn decreases
Back E.M.F decreases and current drawn increases
Back E.M.F and current drawn both increases
Back E.M.F and current drawn both decreases
Q.4.
For constant torque drive which speed control method is preferred ?
Field control
Armature voltage control
Shunt armature control
Mechanical loading system
Q.5.
What will happen if DC shunt motor is connected across AC supply?
Will run at normal speed
Will not run
Will Run at lower speed
Burn due to heat produced in the field winding
Q.6.
The torque developed by a d.c motor is directly proportional to
Flux per pole x Armature current
Armature resistance x Applied voltage
Armature Resistance x Armature current
Square of armature resistance
Q.7.
The shaft torque (Tsh) in a d.c motor is less than total armature torque (Ta) because of ……………. in the motor.
Copper losses
Field Losses
Iron and Friction losses
None of the above
Q.8.
A 4 pole,V, dc series motor has a wave connected armature withconductors. The flux per pole ismWb when the motor is drawingA from the supply. Armature resistance is 0.Ω while series field winding resistance is 0.2 Ω.Calculate the speed under this condition.
1500 RPM
1470 RPM
1300 RPM
1374 RPM
Q.9.
AV, DC shunt motor takes a line current ofA. Resistance of shunt field winding isand resistance of the armature is 0.3 Ω Find the armature current and the back e.m.f.
18.75 A, 245 V
25.32 A, 225 V
15.65 A, 100 V
10 A, 150 V
Q.10.
When the ratio of back E.MF to applied voltage is ___ than the mechanical power develop by the shunt generator is maximum?
1.0
0.5
2
3
Q.11.
If Ta be the armature torque and Ia be the armature current then which of the following relation is valid for DC series motor before saturation?
Ta ∝ Ia
Ta ∝ Ia2
Ta ∝ 1/Ia
Ta ∝ 1/Ia2
Q.12.
Which DC motor is preferred for crane and hoist?
Series motor
Cumulative compound motor
Shunt motor
Differentially compound motor
Q.13.
The starting resistance of D.C motor is generally
High
Infinite
Low
None of the above
Q.14.
Which D.C motor is preferred for machine tools?
Series motor
Cumulative compound motor
Differentially compound motor
Shunt motor
Q.15.
What will happen when the D.C motor is connected to A.C supply then?
D.C motor will run at rated speed
D.C motor will burn
D.C motor will run at slow speed
Both 2 & 3.
Q.16.
The direction of rotation of D.C series motor can be changed by
Interchanging field terminal
Interchanging supply terminal
Both 1&2
None of the above
Q.17.
The application of Differentially compound motor is
Frequent on-off cycle
Low starting torque
High starting torque
Variable speed
Q.18.
The reason for using starter while starting of DC motor is
To restrict armature current as there is no back E.M.F at starting
Motors are not self-starting
Restrict starting torque
None of the above
Q.19.
What will happen when the field of a DC shunt motor gets opened while the motor is running?
Continue to run at the same speed
Speed of motor will be reduced
The motor will attain dangerous high speed
Armature current will be reduced
Q.20.
If the back EMF of DC motor vanishes then
The motor continues to run
Motor will stop
Armature will burn
The motor continues to run in slow speed
Q.21.
Counter EMF of the DC motor is
Less than the applied voltage
More than the applied voltage
Equal to the applied voltage
None of the above
Q.22.
Nowadays DC motor is widely used in
Electric Traction
Air compressor
Centrifugal Pump
Machine shop
Q.23.
A three-point starter is suitable for
Shunt Motor
Series Motor
Shunt & Compound Motor
Shunt, Series, and compound motor
Q.24.
Which of the following rule is used to determine the direction of rotation of D.C motor?
Coloumb’s Law
Lenz’s Law
Fleming’s Right-hand Rule
Fleming’s Left-hand Rule
Q.25.
DC motors get powered from
alternators
batteries
Q.26.
An Electrical machine which converts mechanical energy to electrical energy is called as
motor
generator
capacitor
transformer
Q.27.
The reason for providing field winding of DC motor with thick wire is
To provide large flux
To carry large load current
To reduce eddy current
To increase the flux
Q.28.
Which DC motor is preferred for constant speed?
Series motor
Compound motor
Shunt motor
Differential motor
Q.29.
Magnetic field lines flow
north to south
north to north
south to south
south to north
Q.30.
THE WORKING PRINCIPLE OF DC MOTOR IS---------
MUTUAL INDUCTION
FLEMING'S RIGHT HAND
LORENTZ LAW
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