 # DC Generator mcq Question and Answer

### 1.In an electromechanical energy conversion device, the developed torque 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

stator field and rotor field strengths and the torque angle

Explanation:

### 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

permit mechanical clearance

Explanation:

### 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

the net force and torque on the coil are both zero

Explanation:

### 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

reluctance seen by the working mmf varies

Explanation:

### 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

Synchronizing torque

Explanation:

### 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

Zero

Explanation:

### 7.The emf induced in a conductor rotating in a bipolar field is

• BAC
• CDc and ac both
• DNone of these

AC

Explanation:

### 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

Along the axis of the magnetic field

Explanation:

### 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

Rate of change of flux linkage is maximum

Explanation:

### 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

Square of the armature speed

Explanation:

### 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

Copper loss and stray load loss

Explanation:

### 12.Stray losses are sum of

• AIron and mechanical losses
• BCopper and iron losses
• CCopper and mechanical losses
• DNone of these

Iron and mechanical losses

Explanation:

### 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

Parallel resistance with a high value

Explanation:

### 14.The principle of dynamically induced emf is utilized in

• ATransformer
• BChoke
• CGenerator
• DThermocouple

Generator

Explanation:

### 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

The current and emf in armature conductors are alternating while those at the terminals are unidirectional

Explanation:

### 16.Which of the following is not a part of dc machine?

• AArmature
• BCommutator
• CField winding
• DDamping winding

Damping winding

Explanation:

hints

• AMic
• BCopper
• CCast iron
• DCarbon

Copper

Explanation:

### 18.Laminated yoke in dc motor can reduce

• ASpeed regulation
• BIron loss
• CTemperature rise

Iron loss

Explanation:

### 19.Pole shoe of a dc machine is laminated for the purpose of

• BDecreasing eddy current loss
• CDecreasing both hysteresis and eddy current loss
• DManufacturing ease

Decreasing eddy current loss

Explanation:

### 20.The function (s) of pole shoes in a dc machine is / are 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