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
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