# PHYSICS: D.C. MACHINE 07/08 Online Test

In D.C machines, the armature windings are placed on the rotor because of the necessity for
Commutation
Generation of voltage
Development of torque
Electromechanical energy conversion
An ideal D.C generator has a regulation of
20%
70%
90%
Zero%
What is the number of armature parallel paths in a 4 pole D.C generator having duplex lap will
2
4
8
16
Which of the D.C generators has poorest voltage regulation
Series
Compound
Shunt
Over-compound
Shunt generators are cost suitable for stable parallel operation because of their'
Linear voltage characteristics
Rising voltage characteristics
Identical voltage characteristics
Slightly drooping voltage characteristics
Why the armature coils of a D.C machine are not made of aluminum?
As it is costly
As the thermal conductivity of aluminum is low
As the size of the machine will become more
Because aluminum has low resistivity.
A shunt motor has
Widely varying speed
Approximately constant speed at all loads
Very low speed at high load and high speed at low load
In D.C machine the brushes are placed on
M.N.P
G.N.P
Any of (1) and (2)
None of these
The e.m.f. Induced in the armature of a D.C motor is
Less than 220 volts
More than supply voltage
Less than the supply voltage
Equal to the supply voltage
Wave winding is composed of
Any odd number of conductors
Any even number of conductors
That even nUlJ1ber, which is exact multiple of poles + 2
That even number which is exact multiple of poles
Shunt motor starter resistance is connected in series with
Line
Shunt field winding
Armature winding
All of these
The open circuit voltage of a over-compound generator is 250 V. At full load the terminal voltage
Will always be 250 V
Will be less than 250 V
May be more or less than 250 V
May be greater than 250 V
Armature coil is short-circuited by brushes when it lies
Along field axis
Along neutral axis
In any of the above positions
In none of the above positions
By varying the armature circuit resistance the speed of a d.c. motor can be varied. The motor then becomes a
Variable power drive
Variable torque drive
Constant power drive
Constant torque drive
Which of the following methods is most effective in finding out the no load losses in a large D.C shunt motor?
Leonard test
Block rotor test
Hopkinson's test
Swinburne's test
The starting torque of a D.C series motor is
Less than the starting torque of the shunt motor
More than the starting torque of the shunt motor
Equal to the starting torque of a shunt motor
Equal to zero
Which of the following motor is used to drive the constant speed fans and lathes
D.C shunt motor
A.C series motor
D.C series motor
Cumulative compound motor
A D.C series motor should not be started without some mechanical load on its because
Load on the motor acts as a brake
At no load motor gives vicious sparking
At no load, losses in a series motor are high
A series motor develops infinite speed at no load.
Stray loss in a D.C machine is the sum of
Iron loss and mechanical loss
Copper loss and mechanical loss
Field copper loss and mechanical loss
Armature copper loss and iron loss
Which of the following may constitute short-circuit in the armature winding?
Insulator failure between two commutator segments
Inter turn insulation failure
(1) And or (2)
Loss of residual magnetism
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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nice test

4473 days 1 hours 5 minutes ago

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