DC Generator Quiz

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

(a) 0.005 mm

(b) 0.05 mm

(d) 5 m

Correct! Wrong!

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

(a) speed

(b) load

(d) speed and voltage

Correct! Wrong!

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

(a) mica

(b) copper

(d) carbon

Correct! Wrong!

The armature of D.C. generator is laminated to

(a) reduce the bulk

(b) provide the bulk

(d) reduce eddy current loss

Correct! Wrong!

Copper brushes in D.C. machine are used

(a) where low voltage and high currents are involved

(b) where high voltage and small cur-rents are involved

(d) in none of the above cases

Correct! Wrong!

In D.C. generators, current to the external circuit from armature is given through

(a) commutator

(b) solid connection

(d) none of above

Correct! Wrong!

The number of brushes in a commutator depends on

(a) speed of armature

(b) type of winding

(d) amount of current to be collected

Correct! Wrong!

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

(a) magnetic flux, direction of current flow and resultant force

(b) magnetic flux, direction of motion and the direction of e.m.f. induced

(d) magnetic flux, direction of force and direction of motion of conductor

Correct! Wrong!

The resistance of armature winding depends on

(a) length of conductor

(b) cross-sectional area of the conductor

(d) all of the above

Correct! Wrong!

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

(a) current

(b) voltage

(d) none of above

Correct! Wrong!

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

(a) severe sparking

(b) rough commutator surface

(d) any of the above

Correct! Wrong!

If B is the flux density, I the length of conductor and v the velocity of conductor, then induced e.m.f. is given by

(a)Blv

(b)Blv^2

(c)Bl^2v

(d)Bl^2v^2

Correct! Wrong!

In D.C. generators, lap winding is used for

(a) high voltage, high current

(b) low voltage, high current

(d) low voltage, low current

Correct! Wrong!

Laminations of core are generally made of

(a) case iron

(b) carbon

(d) stainless steel

Correct! Wrong!

Brushes of D.C. machines are made of

(a) carbon

(b) soft copper

(d) all of above

Correct! Wrong!

The insulating material used between the commutator segments is normally

(a) graphite

(b) paper

(d) insulating varnish

Correct! Wrong!

In case of a 4-pole D.C. generator provided with a two layer lap winding with sixteen coils, the pole pitch will be

(a) 4

(b) 8

(d) 32

Correct! Wrong!

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. ?

(a) Lap winding

(b) Wave winding

(d) Depends on other features of design

Correct! Wrong!

The material for commutator brushes is generally

(a) mica

(b) copper

(d) carbon

Correct! Wrong!

In D.C. generators, the brushes on commutator remain in contact with conductors which

(a) lie under south pole

(b) lie under north pole

(d) are farthest from the poles

Correct! Wrong!

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

(a) direction of induced e.m.f.

(b) direction of flux

(d) direction of motion of conductor, if forefinger points along the lines of flux

Correct! Wrong!

In lap winding, the number of brushes is always

(a) double the number of poles

(b) same as the number of poles

(d) two

Correct! Wrong!

In a four-pole D.C. machine

(a) all the four poles are north poles

(b) alternate poles are north and south

(d) two north poles follow two south poles

Correct! Wrong!

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

(a) is amenable to better voltage con-trol

(b) is more stable

(d) has all above features

Correct! Wrong!

The bearings used to support the rotor shafts are generally

(a) ball bearings

(b) bush bearings

(d) needle bearings

Correct! Wrong!

DC Generator Quiz

Your Marks

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

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

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

The armature of D.C. generator is laminated to

Copper brushes in D.C. machine are used

In D.C. generators, current to the external circuit from armature is given through

The number of brushes in a commutator depends on

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

The resistance of armature winding depends on

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

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

If B is the flux density, I the length of conductor and v the velocity of conductor, then induced e.m.f. is given by

In D.C. generators, lap winding is used for

Laminations of core are generally made of

Brushes of D.C. machines are made of

The insulating material used between the commutator segments is normally

In case of a 4-pole D.C. generator provided with a two layer lap winding with sixteen coils, the pole pitch will be

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. ?

The material for commutator brushes is generally

In D.C. generators, the brushes on commutator remain in contact with conductors which

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

In lap winding, the number of brushes is always

In a four-pole D.C. machine

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

The bearings used to support the rotor shafts are generally

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