A. Natural graphite
B. Hard carbon
C. Electro graphitic
D. Metal graphite
Related Mcqs:
- 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 - ____________ is the common method of applying brushes to the commntator?
A. Radial
B. Trailing
C. Reaction
D. All of the above - In D.C. machines, ir order to prevent excessive distortion of field form by the armature reaction, the field mmf must be made____________?
A. equal to that of armature mmf
B. less in comparison with the armature mmf
C. large in comparison with the armature mmf
D. none of the above - Hot rolled sheets have ___________ value of permeability?
A. zero
B. low
C. high
D. none of the above - The noise produced by a ___________ cooled machine is less as the rotor moves in a medium of smaller density?
A. air
B. hydrogen
C. either A. or B.
D. none of the above - In self cooled motors the cooling time constant is about ___________ than the heating time constant because cooling conditions are worse at standstill?
A. 2 to 3 times greater
B. 3 to 4 times greater
C. 4 to 5 times greater
D. none of the above - The laminations of the armature of a D.C. machine are usually ___________ thick?
A. 0.1 to 0.2 mm
B. 0.2 to 0.3 mm
C. 0.3 to 0.4 mm
D. 0.4 to 0.5 mm - The cold rolled grain oriented steel has ___________ permeability in the direction of the grain orientation?
A. minimum
B. maximum
C. nil
D. none of the above - Which of the following is an advantage of hydrogen cooling ?
A. Increase in efficiency
B. Increase in ratings
C. Increase in life
D. Smaller size of coolers
E. All of the above - Disc windings are primarily used in_____________-?
A. short capacity transformers
B. medium capacity transformers
C. high capacity transformers
D. any of the above
