Q.1
Which motor has the poorest speed control?
Q.2
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
0 h : 0 m : 1 s