Electrical Machines - I Mid - I, September - 2014

1.The coupling medium between mechanical energy and electrical energy is
  • Electrical fied
  • Magnetic field
  • Electrostatic field
  • None
Answer: B
2.The generator which converts
  • Mechanical to electrical energy
  • electrical to mechanical energy
  • chemical to mechanical energy
  • electrical to chemical energy
Answer: A
3.The yoke of a dc machine
  • is laminated
  • is not laminated
  • may or may not be laminated
  • is partially laminated
Answer: B
4.The thickness of lamination is about
  • 2 mm
  • 5 mm
  • 0.5 mm
  • 0.1 mm
Answer: C
5.A commutator is made up of
  • only radical
  • only longitudinal
  • both A & B
  • neither A nor B
Answer: B
6.Equiliser rings are used in
  • lap wound machines
  • wave wound machines
  • both A & B
  • none
Answer: A
7.Inter poles are used in
  • lap wound machines
  • wave wound machines
  • both A & B
  • none
Answer: C
8.Series generator can self excited
  • only if load current is zero
  • only if load current is not zero
  • irrespective of the value of load current
  • none
Answer: B
9.A compensating winding is used in
  • all dc generators
  • all dc motors
  • special purpose dc machines
  • A & B
Answer: C
10.When a shunt generator is delivering a certain load current, it's terminal voltage
  • less than open circuit voltage
  • more than o.c voltage
  • may be more or less than o.c voltage
  • Equal to o.c voltage
Answer: A
11.For a lap wouad armature, the number of armature parallel paths is _______________________
Answer: P
12.EMF equation of a DC generator is ________________________________
Answer: E = φZN/60 X P/A
13.The main function of commutator is ________________________________
Answer: to collect dc current and convert in to ac current
14.For a wave wound armature,the number of armature parallel paths is only ______________
Answer: 2
15.The interaction of armature field with the main magnetic field is termed as ______________
Answer: armature reaction
16.The emf produced in a DC generator is ____________________ induced emf.
Answer: magnetically
17.Bearings employed for supporting the rotor shafts are usually ___________ bearings.
Answer: ball or roller
18.The armature reaction in case of an unsaturated DC machine is ________________.
Answer: cross magnetizing
19.Armature current and field current will be equal in case of DC___________ machine.
Answer: series
20.In DC shunt generator the armature current is given as__________________
Answer: Eg-V/Ra