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
The effect of changing the evaporator temperature on COP as compared to that of changing the condenser temperature (in vapour compression refrigeration system) is
A Less pronounced
B More pronounced
C Equal
D Data insufficient, can't be predicted
________ is the common method of applying brushes to the commntator.
A Radial
B Trailing
C Reaction
D All of the above
The speed of a D.C. motor can be varied by varying
A Field current
B Applied voltage
C Resistance in series with armature
D Any of the above
Which of the following brushes can be used for high values of current density ?
A Metal graphite brushes
B Hard carbon brushes
C Electro-graphitic brushes
D Natural graphite brushes
In a metal arc welding process, a gas metal arc welding with magnetized flux is used and can be done in all the positions i.e. flat position, vertical position or inclined position.
A Globular transfer
B Spray transfer
C GMAW practice
D Dip transfer
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
_______ brushes are fragile and cause excessive wear of commutator,
A Natural graphite
B Hard carbon
C Electro graphitic
D Metal graphite
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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