# Physics: Electricity Online Test

In Fleming's right-hand rule, the thumb points towards
Direction of flux
Direction of induced E.M.F
Direction of motion of conductor, if fore finger points along the lines of flux
Direction of motion of the conductor if fore finger points in the direction of generated e.m.f.
The resistance of armature winding depends on
Number of conductors
Conductor length
Cross-sectional area of the conductor
All of the above
The output voltage of a simple D.C generator is
A.C. Square wave
A.C. sinusoidal wave
Pure D.C.
Pulsating D.C.
When two generators are running in parallel and field of one of them is weakened too-much then it will
Deliver large share of the total load
Deliver small share of the total load
Run in the opposite direction
Run as a motor in the same direction
If a shunt generator fails to build up any voltage at no-load, the reason may be that
There is no residual magnetism
Field coil may be connected in reverse direction
Its field resistance is more than the critical resistance
All or anyone of the above
In shunt generator inter pole winding carries
Armature current
Shunt field current
None of these
Due to which of the following reasons a separately excited generator as compared to a self-excited generator is better?
Is more stable
Has exciting current independent of load current
Is amenable to better voltage
Has all above features
Due to which of the following reasons, copper brushes in D.C. machine are used?
When high voltage and small currents are involved
When low voltage and high currents are involved
In both of the above cases
In none of the above cases
To maintain constant D.C. Voltage at the consumers' terminals the generator used is
Series generator
Over compounded generator
Under compounded generator
Flat compound generator
A four-pole lap wound D.C shunt generator is supplying 46 A to a load. The field current of the generator is 2A. The current per parallel path is
12 A
24 A
24 A
None of these
In a duplex wave winding with equalizers
Both number of pole-pairs and number of slots are even
Number of pole-pairs is odd and number of slots is even
Number of pole-pairs is even and number of slots is odd
Both number of pole-pairs and number bf slots are odd
What would be observed if a D.C shunt motor is started with an open-circuited field?
The motor picks up fast and acquires full speed while drawing small current
The motor picks up fast and acquires full speed while drawing large current
The motor does not pick up speed but draws a large current
The motor does not pick up speed but draws a small current
When the series field is so connected that its ampere turns act in the same direction as those of shunt field. the generator is said to be
Series generator
Shunt generator
Cumulatively compound generator
Differentially compound generator.
In a D.C. welding generator has
Wave winding
Duplex winding
Lap winding
Any of the above
In a D.C. generator, the armature reaction results in
Magnetisation of inter poles
Demagnetisation of the centers of poles
Magnetisation of the leading tip and demagnetisation of the trailing pole tip
Demagnetisation of the leading pole tip and magnetisation of the trailing pole tip
Why is the armature of a D.C machine made of silicon steel stampings ?
To reduce eddy current loss
To reduce hysteresis loss
For the ease with which the slots can be created
To achieve high permeability.
The critical resistance in a D.C shunt generator is
The value of field circuit resistance above which the generator would fail to excite
The value of field circuit resistance for which the generator no-load voltage equals the rated voltage
The resistance of the field circuit
The value of field circuit resistance below which the generator would fail to excite
Due to which of the following reasons a twelve pole, lap wound D.C generator be preferred to four-pole lap wound D.C generator?
Low speed
High speed
Higher voltage
Higher current output
The armature coils of a D.C machine are not made of alumil1ium, because
Aluminum is costly
Aluminum has low resistivity
The thermal conductivity of aluminum is low
The size of the machine will become more
In lap winding resultant pitch is
Sum of front and back pitches
Difference of front and back pitches
Division of front pitch by back pitch
Multiplication of front and back pitches.
Description:

This test includes the mixed type of questions from Electricity chapter; specifically the questions from DC Machine are included in this test.

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Discussion

. When tow generators are running in parallel and field of one of them is weakened too much then it will
a) deliver large share of the total load
(b) deliver small share of the total load
(c) run in the opposite direction
(d) run as a motor in the same direction

1920 days 2 hours 40 minutes ago

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