JNTUH PEE SECOND MID BITS
UNIT-5: D.C. Generators
1.The type of compound generator commonly used for obtaining an almost constant terminal voltage is[ ] (a) over compound (b)flat compound (c)cumulative compound (d)under compound [ ]
2. In a DC machine, the number of commutator segments is equal to [ ]
(a)number of conductors (b)number of poles (c)number of coils (d)both a and b
3. The yoke of a dc machine is made up of [ ]
(a)silicon steel (b)soft iron (c)aluminium (d)cast steel
4. The brushes that carry the current to the load are made up of _________
5. Power lost as heat in the armature and field windings of a dc machine is called ___________loss.
6. A shunt generator delivers 195A at a terminal p.d of 250V. The Ra and Rf are 0.02Ω and 50Ω respectively. The generated emf is _________
7. The field winding of a d.c shunt machine usually carries ______ of the rated current of the machine [ ]
(a) 2% to 5% (b) 15% to 20% (c) more than 20% (d) less than 0.5%
8. A shunt generator delivers 195 A at a terminal p.d of 250 V. The armature resistance and shunt field resistance are 0.02Ω and 50Ω respectively. What is the value of generated e.m.f? [ ]
(a) 246 V (b) 270 V (c) 254 V (d) 282 V
9. In a long-shunt compound-wound generator, the shunt field is connected parallel with [ ]
(a) armature (b) parallel combination of armature and series field
(c) series field (d) series combination of armature and series field
10. In a cumulatively compounded generator, the shunt and series fields ______each other
11. The e.m.f equation of a d.c generator in terms of flux, poles etc is given by __________
12. The most economical method of finding no-load losses of a large d.c. machine is Swinburne’s test.
13. The Commutator in a dc machine can be convert [ ]
(a) ac to dc (b) dc to ac (c) both a and b (d) None of the above
14. The emf produced in the dc generator is ____ induced emf [ ]
(a) Statically (b) Dynamically (c) magnetically (d) Electrostatically
15.. DC generator operates on the principle of [ ]
(a) Electromagnetic induction (b) Lenz's law (c) Biov Savart's law (d) none of these
16. Emf equation of generator is ____________________
17. Yoke is made of which material______________
18. Types of windings in dc generator_______________________
19. The Mechanical energy source used to drive a dc generator is called a [ ]
(A) Rotor (B) Prime Mover (C) Alternator (D) Motor drive
20. The nature of current having in the armature of a dc machine is _____ [ ]
a) AC b) DC c) pulsating d) None
21. The induced voltage in a single loop reverses_____ [ ]
a) Once each revolution b) once each half revolution
c) one each quarter revolution d) 8 times each revolution
22. The field of self excited generator is excited by [ ]
a) Dc b) Ac c) By its own current d) Either ac or Dc
23. The magnetic field which initially induces emf in the armature in a self excited dc generator is
Because of ___________________
24. Emf induced in each conductor of a DC Machine is [ ]
A) An alternating emf B) A direct emf
C) A pulsating emf D) Emf of random waveshape
25. The residual magnetism of a DC shunt generator can be regained by [ ]
A) Connecting the shunt field to a battery B) Running the generator on no load for sometime
C) Grounding the shunt field D) Reversing the direction of rotation of the generator.
26. __________________ Law states that the magnitude of individual emf is equal to the rate of
Change of flux linkages.
27. A four pole DC generator is running at 1500 rpm. The frequency of current in the armature is ______________________.
28. The armature of a dc machine is a laminated to reduce _____________________________.
29. The function of interpoles in a dc machine is to________________
30. The EMF induced in a coil rotating in a uniform magnetic field is maximum when the flux linkage by the coil is _______________
31. The O.C.C of a d.c. generator is also called its magnetic or no load saturationcharacteristic.
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