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Laminations of core are generally made of

Laminations of core are generally made of

  1. case iron
  2. carbon
  3. silicon steel
  4. stainless steel
discuss
Which of the following could be lamina-proximately the thickness of laminations of aD.C. machine ?

 Which of the following could be lamina-proximately the thickness of laminations of aD.C. machine ?

  1. 0.005 mm
  2. 0.05 mm
  3. 0.5 m
  4. 5 m
discuss
The armature of D.C. generator is laminated to

The armature of D.C. generator is laminated to

  1. reduce the bulk
  2. provide the bulk
  3. insulate the core
  4. reduce eddy current loss
discuss
The resistance of armature winding depends o

 The resistance of armature winding depends o

  1. length of conductor
  2. cross-sectional area of the conductor
  3. number of conductors
  4. all of the above
discuss
The field coils of D.C. generator are usually made of

The field coils of D.C. generator are usually made of

  1. mica
  2. copper
  3. cast iron
  4. carbon
discuss
The commutator segments are connected to the armature conductors by means of

The commutator segments are connected to the armature conductors by means of

  1. copper lugs
  2. resistance wires
  3. nsulation pads
  4. brazing
discuss
In a commutator

In a commutator

  1. copper is harder than mica
  2. mica and copper are equally hard
  3. mica is harder than copper
  4. none of the above
discuss
In D.C. generators the pole shoes are fastened to the pole core by

 In D.C. generators the pole shoes are fastened to the pole core by

  1. rivets
  2. counter sunk screws
  3. brazing
  4. welding
discuss
Satisfactory commutation of D.C. machines requires

Satisfactory commutation of D.C. machines requires

  1. brushes should be of proper grade and size
  2. brushes should smoothly run in the holders
  3. smooth, concentric commutator properly undercut
  4. all of the above
discuss
Fleming's right-hand rule regarding direction of induced e.m.f., correlates

Fleming's right-hand rule regarding direction of induced e.m.f., correlates

 
  1. magnetic flux, direction of current flow and resultant forcw
  2. magnetic flux, direction of motion and the direction of e.m.f. induced
  3. magnetic field strength, induced voltage and current
  4. magnetic flux, direction of force and direction of motion of conductor
discuss
While applying Fleming's right-hand rule to And the direction of induced e.m.f., the thumb points towards

While applying Fleming's right-hand rule to And the direction of induced e.m.f., the thumb points towards

  1. direction of induced e.m.f.
  2. direction of flux
  3. direction of motion of the conductor if forefinger points in the direction of generated e.m.f.
  4. direction of motion of conductor, if forefinger points along the lines of flux
discuss
The bearings used to support the rotor shafts are generally

The bearings used to support the rotor shafts are generally

  1. ball bearings
  2. bush bearings
  3. magnetic bearmgs
  4. needle bearings
discuss
In D.C. generators, the cause of rapid brush wear may be

In D.C. generators, the cause of rapid brush wear may be

  1. severe sparking
  2. rough commutator surface
  3. imperfect contact
  4. any of the above
discuss
In lap winding, the number of brushes is always

 In lap winding, the number of brushes is always

  1. double the number of poles
  2. same as the number of poles
  3. half the number of poles
  4. two
discuss
For a D.C. generator when the number of poles and the number of armature conductors is fixed, then which winding will give the higher e.m.f. ?

 For a D.C. generator when the number of poles and the number of armature conductors is fixed, then which winding will give the higher e.m.f. ?

  1. Lap winding
  2. Wave winding
  3. Either of (a) and (b) above
  4. Depends on other features of design
discuss
In a four-pole D.C. machine

 In a four-pole D.C. machine

  1. all the four poles are north poles
  2. alternate poles are north and south
  3. all the four poles are south poles
  4. two north poles follow two south poles
discuss
Copper brushes in D.C. machine are used

Copper brushes in D.C. machine are used

  1. where low voltage and high currents are involved
  2. where high voltage and small cur-rents are involved
  3. in both of the above cases
  4. in none of the above cases
discuss
A separately excited generator as compared to a self-excited generator

A separately excited generator as compared to a self-excited generator

  1. is amenable to better voltage con-trol
  2. is more stable
  3. has exciting current independent of load current
  4. has all above features
discuss
In case of D.C. machines, mechanical losses are primary function of

 In case of D.C. machines, mechanical losses are primary function of

  1. current
  2. voltage
  3. speed
  4. none of above
discuss
Iron losses in a D.C. machine are independent of variations in

Iron losses in a D.C. machine are independent of variations in

  1. speed
  2. load
  3. voltage
  4. speed and voltage
discuss
total MCQs: 117

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