Users Also Read
Read MCQ's/Objective questions
MCQ's Search Engine
D.C.Basic
A.C.Basic
A.C.Machine
A.C. Fundamentals
Alternators
Basic Electricity
Control Systems
D.C. Generators
D.C. Motors
Economics of Power Generation
Electric Heating
Electric Traction
Electric Welding
Electrical Engineering Materials
Electrical Installation and Wiring
Electrical Machine Design
Electrostatics
Electrolysis and Storage of Batteries
Electromagnetic Induction
Illumination
Industrial Drives
Magnetic Circuit & Electromagnetism
Measurement and Instrumentation
Network Theorems And Circuit Theory
Polyphase Induction Motors
Resistance and Ohm's law
Rectifiers and Converters
Refrigeration and Air conditioning
Single Phase Induction Motors
Switchgear and Protection
Synchronous Motors
Transformers
Transmission & Dist. of Elect. Power
Home⇒ Engineering⇒
Dc machine
1-Dont try to cram or spend more time here just read it fast and cover syllabus then practice MCQ's cheptor of same topic to check your progress. . |
2-Wrong options are also given but dont concentrate there, Right answer is in bold format. |
Q61 ⇒ A 6-pole lap wound dc machine has 720 conductors and it draws
50 A from supply mains. What is the flux distribution produced
by the armature reaction per pole? Triangular in wave shape with a peak of 500 AT. [other wrong options] [Discuss in forum] Rectangular in wave shape with a peak of 500 AT. Rectangular in wave shape with a peak of 100 AT Triangular in wave shape with a peak of 1000 AT. |
Q62 ⇒ In a dc machine without any bnish shift, the shift of the magnetic
neutral axis owing to armature reaction is in the direction of rotation for the generator and against the direction of rotation for the motor. [other wrong options] [Discuss in forum] in the direction of rotation for both the generator and the
motor against the direction of rotation for both the generator and the motor against the direction of rotation for the generator and in the direction of rotation of motor. |
Q63 ⇒ In a dc machine, the number of mechanical and electrical degrees
will be same when the number of poles on the machine is 2 [other wrong options] [Discuss in forum] 4 8 1 |
Q64 ⇒ In a dc shunt generator working on load, the brushes are moved
forward in the direction of rotation, as a result of this, commutation
will improve but terminal voltage will fall. [other wrong options] [Discuss in forum] worsen and terminal voltage will fall. improve and terminal voltage will rise. worsen and terminai voltage will rise. |
Q65 ⇒ In large sized dc machines the
compensating windings are provided
to neutralize the voltageinduced in the coil due to high fluctuation of load. [other wrong options] [Discuss in forum] compensate for the decrease in speed due to increase of ioad. reduce eddy current losses by providing local short-circuits. none of the above. |
Q66 ⇒ Sparkless commutation can he achieved by employing any one or more of the above methods. [other wrong options] [Discuss in forum] interpoles. compensating winding. high resistance carbon brushes. |
Q67 ⇒ A dc machine is provided with both interpole and compensating
windings. These two windings with respect to armature circuit
will be in series. [other wrong options] [Discuss in forum] parallel. former in series and the latter in parallel. former in parallel and the latter in series. |
Q68 ⇒ In dc machines, the interpoles are prorided both (e) and (d). [other wrong options] [Discuss in forum] for mechanical
balancing of machines. to counteractthe demagnetizing effect of armature mmf in the commutating zone. to counteract the reactance voltage and the cross-magnetizing effect of armature mmf in the commutating zone. to make commutation sparkless. |
Q69 ⇒ The magnetic field which initially induces emf in the armature in a
self excited dc generator ïs because of residual magnetism [other wrong options] [Discuss in forum] permanent magnets armature rotation none of the above. |
Q70 ⇒ The series field of a short shunt dc generator is excited by___
current. load [other wrong options] [Discuss in forum] armature shunt field battery |
Q71 ⇒ The factor that is not responsible for drop in terminal voltage of a
dc shunt generator on load is commutation. [other wrong options] [Discuss in forum] armature reaction. armature resistance drop. field weakening due to (b) and (c). |
Q72 ⇒ A dc series generator is provided with divertor and is delivering its
rated current, If the divertor switch is opened, the terminal voltage
will increase. [other wrong options] [Discuss in forum] remain constant. decrease. none of these. |
Q73 ⇒ Over or under compounding of a dc generator is achieved by shunting more or less current froni the series field. [other wrong options] [Discuss in forum] shunting more or less current from the shunt field. connecting it as long shunt. connecting it as short-shunt. |
Q74 ⇒ In a dc compound generator, "flat compound" characteristic,
required for certain applications, maybe obtained by connecting a
variable resistance: across the series field. [other wrong options] [Discuss in forum] in series with the series field. in parallel with the shunt field. in series with the shunt field. |
Q75 ⇒ The type of dc generator used for arc welding purposes is a differentially compounded generator [other wrong options] [Discuss in forum] series generator. shunt generator. cumulatively compounded generator. |
Q76 ⇒ An exciter for turbo-generator is a dc____ generator. Shunt [other wrong options] [Discuss in forum] Series Compound separately excited |
Q77 ⇒ In parallel operation of two dc compound generators provided
with interpoles, the equalizing bar must be connected to junction of series and interpole fields. [other wrong options] [Discuss in forum] inter pole fields only series fields only. none of the above. |
Q78 ⇒ A dc shunt generator when driven without connecting field winding
shows au open-circuit terminai voltage of 12 V. When field winding
is connected and excited the terminal voltage drops to zero because field winding has got wrongly connected. [other wrong options] [Discuss in forum] field resistance is higher than critical resistance. there is no residual magnetism in the field circuit. there is a fault in armature circuit. |
Q79 ⇒ If the back emf in a dc motor vanishes suddenly, the motor will burn. [other wrong options] [Discuss in forum] start hunting run at very high speed. run at very slow speed. |
Q80 ⇒ If field of one of two generators operating in parallel is made very
weak, then it will operate as a motor and run in the same direction. [other wrong options] [Discuss in forum] not take any load. take major share of load operate as a motor and run in the opposite direction. |
Or |