300 Important DC Generator MCQ Question and Answer | PDF Free Download
1.Torque developed in an electromechanical energy conversion device depends upon
- Astator field strength and torque angle
- Bstator field and rotor field strengths
- Cstator field and rotor field strengths and the torque angle
- Dstator field strength only
2.In electromechanical energy conversion devices (e.g generators and motors) a small air gap is left between the stator and the rotor in order to
- Areduce the reluctance of the magnetic path
- Bincrease flux density in the air gap
- Cpermit mechanical clearance
- Davoid saturation of field
3.If a current carrying coil is placed in a uniform magnetic field direction of magnetic induction, then
- Athe net force and torque on the coil are both zero
- Bthe net force is zero but torque is finite
- Cthe net force is finite but toque is zero
- Dthe net force and torque are both finite
4.Reluctance torque in rotating machines is present, when
- Aair gap is not uniform
- Breluctance seen by stator mmf varies
- Creluctance seen by rotor mmf varies
- Dreluctance seen by the working mmf varies
5.A rotating electrical machine having its self-inductances of both the stator and the stator windings, independent of rotor position will definitely not develop.
- AStarting torque
- BSynchronizing torque
- CHysteresis torque
- DReluctance torque
6.A circular metallic disc is placed in a vertical magnetic field of constant induction in the downward direction. If the disc is rotated in a horizontal plane, the emf induced will be
- AZero
- BConstant independent of disc size
- CIncreasing radially in the outward direction
- DDecreasing radially in the outward direction
7.The emf induced in a conductor rotating in a bipolar field is
- ADC
- BAC
- CDc and ac both
- DNone of these
8.A conductor is rotating within a magnetic field. At which of the position do the peak voltages occur?
- AAt right angles to the axis of magnetic field
- BAlong the axis of the magnetic field
- CAt 450 angles to the axis of magnetic field
- DAnywhere
9.EMF induced ina coil rotating in a uniform magnetic field will be maximum when the
- AFlux linking with the coil is maximum
- BRate of change of flux linkage is minimum
- CRate of change of flux linkage is maximum
- DRate of cutting flux by the coil sides is minimum
10.In a dc motor the windage loss is proportional to
- ASupply voltage
- BSquare of the supply voltage
- CSquare of the flux density
- DSquare of the armature speed
11.Which of the following are the variable losses in a rotating machine?
- ACore loss and mechanical loss
- BCore loss and stray load loss
- CCopper lossand core loss
- DCopper loss and stray load loss
12.Stray losses are sum of
- AIron and mechanical losses
- BCopper and iron losses
- CCopper and mechanical losses
- DNone of these
13.Generally, the no ? load losses of an electrical machine is represented in its equivalent circuit by
- AParallel resistance with a low value
- BSeries resistance with a low value
- CParallel resistance with a high value
- DSeries resistance with a high value
14.The principle of dynamically induced emf is utilized in
- ATransformer
- BChoke
- CGenerator
- DThermocouple
15.In a dc machine
- AThe current and emf in armature conductors are alternating while those at the terminals are unidirectional
- BThe current and emf in armature conductors are unidirectional while those at the terminals are alternating
- CThe current and emf in armature conductors and at the terminals are unidirectional
- DThe emf in armature conductors and at the terminals is alternating while current there is unidirectional
16.Which of the following is not a part of dc machine?
- AArmature
- BCommutator
- CField winding
- DDamping winding
17.The field coils of a dc generator are usually made of
- AMic
- BCopper
- CCast iron
- DCarbon
18.Laminated yoke in dc motor can reduce
- ASpeed regulation
- BIron loss
- CTemperature rise
- DSparking non load
19.Pole shoe of a dc machine is laminated for the purpose of
- ADecreasing hysteresis loss
- BDecreasing eddy current loss
- CDecreasing both hysteresis and eddy current loss
- DManufacturing ease
20.The function of pole shoes in a dc machine is to
- ASupport the field coils
- BReduce the reluctance of the magnetic path
- CSpread out the flux to achieve uniform flux distribution in the air gap
- DAll of the above