DC Generators

Laminations of core are generally made of

• case iron

• carbon

• silicon steel

• stainless steel

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

• 0.005 mm

• 0.05 mm

• 0.5 mm

• 5 mm

The armature of D.C. generator is laminated to

• reduce the bulk

• provide the bulk

• insulate the core

• reduce eddy current loss

The resistance of armature winding depends on

• length of conductor

• cross-sectional area of the conductor

• number of conductors

• all of the above

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

• mica

• copper

• cast iron

• carbon

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

• copper lugs

• resistance wires

• insulation pads

• brazing

In a commutator

• copper is harder than mica

• mica and copper are equally hard

• mica is harder than copper

• none of the above

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

• rivets

• counter sunk screws

• brazing

• welding

According to Fleming’s right-hand rule for finding the direction of induced e.m.f., when middle finger points in the direction of induced e.m.f., forefinger will point in the direction of

• motion of conductor

• lines of force

• either of the above

• none of the above

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

• magnetic flux, direction of current flow and resultant force

• magnetic flux, direction of motion and the direction of e.m.f. induced

• magnetic field strength, induced voltage and current

• magnetic flux, direction of force and direction of motion of conductor