PHYSICS: D.C. MACHINE 06/08 Online Test

Which of the following motors should not be used for centrifugal pumps
Series
Shunt
Differentially compound
Cumulating compound
Which of the following tests can be used to measure stray losses of a D.C motor?
Field's test
Brake test
Swinburne's test
Running down test
In a D.C motor, the speed is
Constant
Directly proportional to back e.m.f.
Directly proportional to field flux
Inversely proportional to the product of back e.m.f and flux
In D.C machine, there are as many commutator bars as the number of
Poles
Slots
Armature conductors
Winding elements
Shunt field of a compound generator being connected across both the series field and armature, the connection is known as
Long shunt
Short shun
Differential compounding
Cumulative compounding
Which of the following tests can be conducted on all types of D.C machines of lower rating?
Field's test
Brake test
Running down set
Swinburne's test
A simple method of increasing the voltage of a D.C generator is
To increase the speed of rotation
To decrease the speed of rotation
To increase the length of the armature
To decrease the length of the armature
In D.C generator the change in voltage when the load is reduced from rated value to zero, expressed as a percentage of rated load voltage, is known as
Loss factor
Regulation
Efficiency
Armature reactance
A D.C shunt motor is running at its rated speed, suddenly the field winding gets open
Its speed decreases slowly
Motor will stop immediately
Motor speed becomes momentarily high and then it reduces to zero
Motor speed becomes momentarily high and then it will be running at normal speed
No volt release coil of D.C shunt motor starter is connected in series with the
Line
Series winding
Shunt field winding
Armature winding
Small air gap between stator and armat.ure
Reduces noise
Provides high ventilation
Provide stronger magnetic field
facilate high speed operation
No load losses of a shunt motor can be determined by
Brake test
Retardation test
Hopkinsen's test
Swinburne's test
A D.C shunt motor is supplying a load at its rated speed. Its speed can be decreased by
Using field regulator
Increasing the supply voltage
Adding an external resistance in the field circuit
Connecting additional resistance in series of the armature
The direction of rotation of a D.C shunt motor can be reversed by interchanging
The field terminals only
The supply terminals
The armature terminals only
Either field or armature terminals
Once the residual magnetism of a shunt generator is lost accidentally, it may be restored t connecting its shunt field
To earth
To an alternator
In reverse
To a external battle
Which generator fails to build up voltage if there is no residual magnetism?
Separately excited generator
Series generator
Shunt generator
All of the above
For a cumulatively compounded D.C motor, speed control can be effected through
Change of field resistance
Change of armature resistance
Change of armature voltage
Any of the above
The series field of a short-shunt D.C generator is excited by
Load current
Shunt current
External current
Armature current
Lf the no load voltage of a certain generator is 220 V and the rated voltage is 200 V, then the voltage regulation is nearly
0%
10%
15%
20%.
The speed of a D.C shunt motor can be increased above its rated speed by
Increasing the supply voltage
Increasing the flux per pole
Using field regulator
Connecting additional resistance in series of the armature
Description:

This is test is a part of a series of eight test which helps students to check the level of knowledge in Electricity, specifically in the DC Machine in Physics.

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