Q.1
Types of DC motor.
  • Compound field winding Motor
  • Series field winding Motor
  • Shunt field winding Motor
  • All of the above
Q.2
A brushless motor is more efficient than a brushed motor because...
  • There is less energy lost inside the motor due to friction and heat.
  • There is less power used to spin the motor.
  • There is less noise created in spinning the motor.
  • This is an incorrect statement. Brushed motors are more efficient.
Q.3
You can tell that an electric motor is brushless because it has...
  • 1 wire attached to it.
  • 2 wires attached to it.
  • 3 wires attached to it.
  • No wires attached to it.
Q.4
The part of an electric motor that doesn't spin is called the...
  • armature
  • commutator
  • stator
  • bearings
Q.5
A simple DC electric motor is fitted with a coil that rotates in a magnetic field. A commutator connects the power supply to the coil.What is the purpose of the commutator?
  • It converts AC into DC in the coil.
  • It prevents the current from becoming too great, because the coil has a low resistance
  • It reverses the direction of the current in the coil after every 180° rotation of the coil
  • It switches the current off momentarily after every 90° rotation of the coil
Q.6
______________ magnets are created by passing a current through a wire.
  • compass magnets
  • electromagnets
  • DC Motor Magnets
Q.7
_____________________ a device used to convert electric energy into mechanical energy.
  • Motor
  • Direct Current
  • Alternating Current
  • Compass
Q.8
The current drawn by the armature of DC motor is directly proportional to ________________
  • Torque
  • Speed
  • The voltage across the terminals
  • Cannot be determined
Q.9
In case of parallel field connection, it won’t rotate at all and will start humming and will create vibrations, as a torque produced by positive and negative cycle will cancel out each other. DC motor will be heated up and it may burn.
  • Winding
  • Shaft
  • Commutator
  • Stator
Q.10
In DC motor, which of the following part can sustain the maximum temperature rise?
  • Field winding
  • Commutator
  • Slip rings
  • Armature winding
Q.11
Eddy current are induced in the pole shoes of a DC machine due to
  • Oscillating magnetic field
  • Pulsating magnetic flux
  • Relative rotation between field and armature
  • None of the above
Q.12
Direction of rotation of motor is determined by ____________
  • Faraday’s law
  • Lenz’s law
  • Coulomb’s law
  • Fleming’s left-hand rule
Q.13
The speed of a DC motor is ________
  • Directly proportional to flux per pole
  • Inversely proportional to flux per pole
  • Inversely proportional to applied voltage
  • None of the above
Q.14
The value of back e.m.f in a DC motor is maximum at _______
  • No load
  • Full load
  • Half load
  • None of the above
Q.15
The field poles and armature of a DC machine are laminated to _________
  • Reduce the weight of the machine
  • Decrease the speed
  • Reduce eddy currents
  • Reduce armature reaction
Q.16
The speed of DC motor is
  • Always constant
  • Directly proportional to back e.m.f
  • Directly proportional to flux
  • Inversely proportional to the product of back e.m.f and flux
0 h : 0 m : 1 s