NEW
Font size
WorksheetsSessional Test 1 B.Voc Mechatronics
Total questions: 20
Worksheet time: 23mins
The field coils of D.C. generator are usually made of
mica
copper
cast iron
carbon
Material for commutator brushes is generally
mica
copper
cast iron
carbon
The e.m.f. generated by a shunt wound D.C. generator is E. Now while pole flux remains constant, if the speed of the generator is doubled, the e.m.f. generated will be
E/2
E
2E
slightly less than E
In a D.C. generator, critical resistance refers to the resistance of
Brushes
Field
Armature
Load
A 220V dc generator is run at full speed without any excitation. Open Circuit Voltage will be
0 V
about 2 V
220 V
About 50 V
In a shunt generator which of the following relations is true?
Ia= IL+Ish
IL= Ia+Ish
IL-Ia= Ish
IL+Ia+Ish=0
In a 240V dc motor, back emf is 220 V and armature resistance Ra=0.5 ohms, then its armature current is
20 A
10 A
80 A
40 A
Generation of emf takes place in the _______ of dc machine
Armature winding
Field Winding
Pole Cores
Brushes
_______ number of conductors constitute one turn of a coil.
2
4
1
None of the above
______ motor cannot be started on no-load.
DC series
DC shunt
DC compound
None of the above
Field winding of ______ generator has thick wire of less number of turns.
Series
Shunt
Compound
None of the above
Back emf in a motor is due to
Generating action
Motoring action
Reverse action
None of the above
A shunt generator can self-excite
Only if the resistance of the field circuit is less than critical value
Only if the resistance of the field circuit is greater than critical value
Irrespective of the value of the resistance in the field circuit
none of the above
If a D.C. motor is to be selected for conveyors, which motor would be preferred ?
DC Series
DC Shunt
Differentially compound motor
Cumulative compound motor
For the same output rating and full load speed, following motor has poor starting torque
Series
Differential compound
Cumulative compound
Shunt
As the load is increased, the speed of D.C. shunt motor will
Reduce slightly
Increase slightly
Increase proportionately
Remain unchanged
D.C. shunt motors are used for driving
Trains
Cranes
Hoists
Machine tools
Which of the following losses are significantly reduced by laminating the core of a D.C. generator ?
Hysteresis losses
Eddy current losses
Copper losses
Windage losses
Due to the effect of armature reaction in d.c. machine, the value of generated voltage and flux per pole
Increases, decreases
Decreases, decreases
Decreases, increases
Increases, increases
Which one of the following is not the function of pole shoes in a D.C. machine ?
To reduce eddy current loss
To support the field coils
To spread out flux for better uniformity
To reduce the reluctance of the magnetic path
