309.  The purpose of providing dummy coils in a generator is
A. to enhance flux density
B. to amplify voltage
C. to provide mechanical balance for the rotor
D. to reduce eddy currents

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310.  In a D.C. generator, the armature reaction results in
A. demagnetisation of the centres of poles
B. magnetisation of interpoles
C. demagnetisation of the leading pole tip and magnetisation of the trailing pole tip
D. magnetisation of the leading tip and demagnetisation of the trailing pole tip

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311.  In a D.C. generator is case the brushes are moved so as to bring them in magnetic neutral axis, thcn, there will be
A. demagnetization
B. cross-magnetisation
C. cross-magnetisation as well as demagnetization
D. none of the above

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312.  The polarity of a D.C. generator can be reversed by
A. reversing the field current
B. increasing field current
C. reversing field current as well as direction of rotation
D. any of the above

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313.  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

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314. 1n a lap wound D.C. generator having p as number of poles and Z as number of conductors, the maximum number of equilizer rings will be
A. Z
B. p
C.2Z
D.2p

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315. If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be
A. demagnetisation only
B. cross magnetisation as well as magnetization
C. crossmagnetisation as well as demagnetizing
D. cross magnetisation only

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