Related Questions

If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be
A Demagnetization only
B Cross magnetization as well as magnetization
C Cross-magnetization as well as demagnetizing
D Cross magnetization only
_______ brushes are fragile and cause excessive wear of commutator,
A Natural graphite
B Hard carbon
C Electro graphitic
D Metal graphite
The material for commutator brushes is generally
A Mica
B Copper
C Cast iron
D Carbon
In D.C. generators, the brushes on commutator remain in contact with conductors which
A Lie under South Pole
B Lie under North Pole
C Lie under interpolar region
D Are farthest from the poles
In lap winding, the number of brushes is always
A Double the number of poles
B Same as the number of poles
C Half the number of poles
D Two
In case of D.C. machine winding, number of commutator segments is equal to
A Number of armature coils
B Number of armature coil sides
C Number of armature conductors
D Number of armature turns
For both lap and wave windings, there are as many commutator bars as the number of
A Slots
B Armature conductors
C Winding elements
D Poles
Electrical contact materials used in switches, brushes, relay must possess
A High thermal conductivity and high melting point
B Low thermal conductivity and low melting pointL
C High thermal conductivity and low melting point
D Low thermal conductivity and high melting point
The rapid wear of brushes takes place due to
A Abrasion from dust
B Excessive spring pressure
C Rough commutator bars
D All of the above factors
To achieve sparkless commutation brushes of a D.C. generator are rockedm ahead so as to bring them
A Just ahead of magnetic neutral axis
B In magnetic neutral axis
C Just behind the magnetic neutral axis
D None of the above

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