Which of the following is the unit of magnetic flux density ?
none of the above
lumens
weber
tesla
tesla
Which motor is normally free from mechanical and magnetic vibrations ?
Split phase motor
Universal motor
Hysteresis motor
Shaded pole motor
Hysteresis motor
Which of the following motors is used in tape-recorders ?
Hysteresis motor
Universal motor
Capacitor-run motor
Reluctance motor
Hysteresis motor
In a universal motor the most common cause of brush sparking is
all of the above
shorted armature winding
open armature winding
shorted field winding”
all of the above
If starting winding of a single-phase induction motor is left in the circuit it will
run slower
draw excessive current and overheat
run faster
spark at light loads
draw excessive current and overheat
Most of the fractional horsepower motors have either
plain or sleeve bearings
hard and annealed bearings
ball or roller bearings
soft and porous bearings
plain or sleeve bearings
Which of the following statements regarding reluctance-start motor is incorrect ?
the air-gap between rotor and salient poles is non- uniform
So far as its basic working principle is concerned it is similar to shaded pole motor
It is basically an induction motor and not a synchronous one
It is similar to reluctance motor
It is similar to reluctance motor
To reverse the direction of rotation of acapacitor start motor while it is running we should
disconnect motor from supply and immediately reconnect it to supply with reversed connections of the main winding
reverse the direction of connection of the auxiliary winding and after motor comes to rest then connect auxiliary winding to the supply
disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding
reverse the direction of connections of the auxiliary winding and immediately connect it to supply
disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding
In case of a reluctance motor when the load is increased so that it cannot maintain synchronous speed the motor will
run as induction motor
fall out of synchronism and come to stand still
draw excessive armature current and may burn out
become unstable
run as induction motor
If a D.C. series motor is operated on A.C. supply it will
all of the above
have poor efficiency
spark excessively
have poor power factor
all of the above
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