DC Generator

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  • 1/76 Questions

     A D.C. generator works on the principle of

    • Lenz's law
    • Ohm's law
    •  Faraday's law of electromagnetic induction
    • None of the above
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DC Generator - Quiz

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  • 2. 

    If B is the flux density, I the length of conductor and v the velocity of conductor, then induced e.m.f. is given by

    • Blv 

    • Blv2

    • Bl2v 

    • Bl2v2

    Correct Answer
    A. Blv 
    Explanation
    The correct answer is Blv. According to Faraday's law of electromagnetic induction, the induced electromotive force (emf) is directly proportional to the magnetic flux density (B), the length of the conductor (l), and the velocity of the conductor (v). Therefore, the correct equation for the induced emf is Blv.

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  • 3. 

    A shunt generator running at 1000 r.p.m. has generated e.m.f. as 200 V. If the speed increases to 1200 r.p.m., the generated e.m.f. will be nearly

    • 150 V

    • 175 V

    • 240 V

    • 290 V

    Correct Answer
    A. 240 V
    Explanation
    When the speed of a shunt generator increases, the generated e.m.f. also increases. This is because the generated e.m.f. is directly proportional to the speed of the generator. In this case, the speed increases from 1000 r.p.m. to 1200 r.p.m., which is a 20% increase. Therefore, the generated e.m.f. will also increase by approximately 20%. Since the initial e.m.f. is 200 V, a 20% increase would result in an e.m.f. of 240 V.

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  • 4. 

    The insulating material used between the commutator segments is normally

    • Graphite

    • Paper

    • Mica

    • Insulating varnish

    Correct Answer
    A. Mica
    Explanation
    Mica is commonly used as an insulating material between the commutator segments. Mica is a mineral with excellent electrical insulation properties, high heat resistance, and good mechanical strength. It can withstand high temperatures and does not conduct electricity, making it an ideal choice for insulating the segments of a commutator. Mica is also resistant to chemicals and moisture, which further enhances its suitability for this application. Overall, mica provides the necessary insulation and protection to ensure the proper functioning of the commutator in electrical devices.

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  • 5. 

    The bearings used to support the rotor shafts are generally

    • Ball bearings

    • Bush bearings

    • Magnetic bearings

    • Needle bearings

    Correct Answer
    A. Ball bearings
    Explanation
    Ball bearings are commonly used to support rotor shafts because they provide smooth and efficient rotation. They consist of balls enclosed within a ring, which reduces friction and allows for high-speed operation. Ball bearings can handle both radial and axial loads, making them suitable for various applications. Additionally, they are durable and require minimal maintenance.

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  • 6. 

    Function of _____ is to collect current from the commutator and supply it to the external load.

    • Field magnet

    • Armature

    • Brushes

    • Yoke

    Correct Answer
    A. Brushes
    Explanation
    Brushes are used in a DC motor to collect current from the commutator and transfer it to the external load. The commutator is a rotating device that switches the direction of the current in the armature coil, and the brushes make contact with the commutator segments to collect the current. The brushes are typically made of carbon or graphite, which have good electrical conductivity and can withstand the friction and heat generated during operation. By collecting the current from the commutator, the brushes ensure that the electrical power generated by the motor is transferred to the external load efficiently.

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  • 7. 

    The insulating material used between the commutator segments is normally

    • graphite 

    • Paper

    • Mica

    • insulating varnish

    Correct Answer
    A. Mica
    Explanation
    Mica is commonly used as an insulating material between the commutator segments because of its excellent electrical insulation properties. It has a high dielectric strength, which allows it to withstand high voltage without conducting electricity. Mica is also resistant to heat, chemicals, and moisture, making it a durable and reliable choice for insulating the commutator. Additionally, mica is a good thermal conductor, allowing it to dissipate heat effectively and prevent overheating of the commutator. Overall, mica is a suitable material for insulating the commutator, ensuring proper functioning and longevity of the electrical device.

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  • 8. 

    The bearings used to support the rotor shafts are generally

    • ball bearings 

    • Bush bearings

    • Magnetic bearmgs

    • needle bearings

    Correct Answer
    A. ball bearings 
    Explanation
    Ball bearings are generally used to support the rotor shafts. Ball bearings consist of small metal balls that are held in a ring and allow for smooth rotation with minimal friction. They are commonly used in various applications where high radial and axial loads need to be supported. In the case of rotor shafts, ball bearings provide a reliable and efficient means of supporting the shafts and facilitating smooth rotation.

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  • 9. 

    Satisfactory commutation of D.C. machines requires  

    • Brushes should be of proper grade and size

    • Brushes should smoothly run in the holders

    • Smooth, concentric commutator properly undercut

    • All of the above

    Correct Answer
    A. All of the above
    Explanation
    To achieve satisfactory commutation in D.C. machines, all of the mentioned factors are important. Brushes should be of proper grade and size to ensure good contact with the commutator. They should also smoothly run in the holders to avoid any friction or sparking. The commutator should be smooth and concentric, with proper undercutting to ensure effective switching of current between the armature coils. Therefore, all of the above factors are necessary for satisfactory commutation in D.C. machines.

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  • 10. 

    A motor converts

    • Mechanical energy into electrical energy

    • Chemical energy into electrical energy

    • Electrical energy into Mechanical energy

    • Electrical energy into chemical energy

    Correct Answer
    A. Electrical energy into Mechanical energy
    Explanation
    A motor is a device that uses electrical energy to produce mechanical energy. It does this by converting the electrical energy into rotational motion, which can be used to drive machinery or perform other mechanical tasks. This process is achieved through the interaction of magnetic fields and electric currents in the motor's components. Therefore, the correct answer is "Electrical energy into Mechanical energy."

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  • 11. 

    In case of D.C. machines, mechanical losses are primary function of

    • Current

    • Voltage

    • Speed

    • None of above

    Correct Answer
    A. Speed
    Explanation
    In D.C. machines, mechanical losses primarily depend on the speed of the machine. This is because mechanical losses include friction and windage losses, which are caused by the movement of mechanical components such as bearings, brushes, and rotating parts. The faster the machine operates, the higher the friction and windage losses will be, resulting in more mechanical losses. Therefore, speed is the primary factor that determines the level of mechanical losses in D.C. machines.

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  • 12. 

    In case of D.C. machines, mechanical losses are primary function of

    • current 

    • Voltage

    • Speed

    • none of above

    Correct Answer
    A. Speed
    Explanation
    In D.C. machines, mechanical losses primarily depend on the speed of the machine. This is because mechanical losses are caused by friction and windage, which increase as the speed of the machine increases. Therefore, the higher the speed of the D.C. machine, the greater the mechanical losses.

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  • 13. 

    D.C. generators are connected to the busbars or disconnected from them only under the floating condition

    • to avoid sudden loading of the primemover

    • To avoid mechanicaljerk to the shaft

    • To avoid burning of switch contacts

    • all above

    Correct Answer
    A. all above
    Explanation
    The correct answer is "all above". D.C. generators are connected to the busbars or disconnected from them only under the floating condition to avoid sudden loading of the prime mover, to avoid mechanical jerk to the shaft, and to avoid burning of switch contacts. By keeping the generators in a floating condition, these potential issues can be prevented, ensuring the smooth operation and longevity of the generator system.

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  • 14. 

    The following is (are) the part(s) of a field magnet.

    • Yoke

    • Pole cores

    • Pole shoes

    • All of the above

    Correct Answer
    A. All of the above
    Explanation
    The correct answer is "All of the above." This means that all the options mentioned - yoke, pole cores, and pole shoes - are parts of a field magnet. A field magnet typically consists of these components, which work together to generate a magnetic field. The yoke provides a closed magnetic circuit, while the pole cores and pole shoes help concentrate and direct the magnetic field in a desired manner. Therefore, all of these parts are essential for the functioning of a field magnet.

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  • 15. 

    In a four-pole D.C. machine

    • all the four poles are north poles

    • Alternate poles are north and south

    • All the four poles are south poles

    • two north poles follow two south poles

    Correct Answer
    A. Alternate poles are north and south
    Explanation
    In a four-pole D.C. machine, the correct answer is "alternate poles are north and south." This means that the machine has two north poles and two south poles, with each pole alternating in polarity. This arrangement allows for the creation of a magnetic field that is essential for the operation of the machine. By having alternating north and south poles, the machine can generate the necessary electromagnetic forces required for its functioning.

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  • 16. 

    The brushes are ____ in shape.

    • Triangular

    • Rectangular

    • Cylindrical

    • Square

    Correct Answer
    A. Rectangular
    Explanation
    The correct answer is rectangular because the word "brushes" implies that there are multiple brushes, and the shape of each brush is described as rectangular.

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  • 17. 

    In lap winding, the number of brushes is always

    • double the number of poles

    • Same as the number of poles

    • Half the number of poles

    • two

    Correct Answer
    A. Same as the number of poles
    Explanation
    In lap winding, the number of brushes is always the same as the number of poles. This is because in lap winding, each coil is connected to two adjacent commutator segments, and each commutator segment is connected to a brush. Therefore, the number of brushes required is equal to the number of poles.

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  • 18. 

    With a D.C. generator which of the following regulation is preferred?

    • 100% regulation

    • Infinite regulation

    • 50% regulation

    • 1% regulation

    Correct Answer
    A. 1% regulation
    Explanation
    In the context of a D.C. generator, regulation refers to the ability of the generator to maintain a constant output voltage under varying load conditions. A 1% regulation means that the generator can maintain its output voltage within 1% of the rated voltage even when the load changes. This level of regulation is preferred because it indicates a high level of stability and accuracy in the generator's performance, ensuring consistent and reliable power supply.

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  • 19. 

    Which one do you like?

    • Option 1

    • Option 2

    • Option 3

    • Option 4

    Correct Answer
    A. Option 1
  • 20. 

    The following magnet is used in large machines to create magnetic flux

    • Permanent magnet

    • Electro magnet

    • Temporary magnet

    • Any of the above

    Correct Answer
    A. Electro magnet
    Explanation
    Electro magnets are used in large machines to create magnetic flux. Unlike permanent magnets, electro magnets are made by passing an electric current through a coil of wire, which generates a magnetic field. This magnetic field can be controlled and adjusted by varying the amount of current passing through the coil, making electro magnets suitable for use in large machines where magnetic flux needs to be created and manipulated. Permanent magnets, on the other hand, have a fixed magnetic field and cannot be easily adjusted or turned on/off like electro magnets. Temporary magnets are also not commonly used in large machines for creating magnetic flux.

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  • 21. 

    In a D.C. generator the number of mechanical degrees and electrical degrees will be the same when    

    • R.p.m. is more than 300

    • r.p.m. is less than 300

    • Number of poles is 4

    • Number of poles is 2

    Correct Answer
    A. Number of poles is 2
    Explanation
    In a D.C. generator, the number of mechanical degrees and electrical degrees will be the same when the number of poles is 2. This means that for every mechanical degree the rotor moves, the electrical degrees also change by the same amount. This is because in a 2-pole generator, each pole represents 180 electrical degrees. Therefore, when there are 2 poles, the mechanical and electrical degrees will be in sync.

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  • 22. 

    To produce dynamically induced emf, the following is (are) necessary

    • A magnetic field

    • A conductor

    • Motion of conductor with respect to the field

    • All of the above

    Correct Answer
    A. All of the above
    Explanation
    For the production of dynamically induced emf, all three factors mentioned in the options are necessary. A magnetic field is required to create a flux, a conductor is needed to allow the flow of electrons, and the motion of the conductor with respect to the field is necessary to induce the emf. Therefore, all of the above options are essential for the production of dynamically induced emf.

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  • 23. 

    In D.C. generators, the cause of rapid brush wear may be

    •  Severe sparking

    •  Rough commutator surface

    • Imperfect contact

    • Any of the above

    Correct Answer
    A. Any of the above
    Explanation
    The correct answer is "Any of the above". This means that the cause of rapid brush wear in D.C. generators can be any of the mentioned factors: severe sparking, rough commutator surface, or imperfect contact. Each of these factors can contribute to increased friction and wear on the brushes, leading to their rapid deterioration.

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  • 24. 

    Brushes of D.C. machines are made of

    • carbon 

    • Soft copper

    • Hard copper 

    • all of above

    Correct Answer
    A. carbon 
    Explanation
    The brushes of D.C. machines are made of carbon. Carbon brushes are commonly used in D.C. machines because carbon is a good conductor of electricity and has low friction characteristics. It can withstand high temperatures and is durable, making it suitable for the constant sliding contact with the commutator in D.C. machines. Soft copper and hard copper are not typically used for brushes in D.C. machines.

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  • 25. 

    In case of a 4-pole D.C. generator provided with a two layer lap winding with sixteen coils, the pole pitch will be

    • 4 

    • 8

    • 16 

    • 32

    Correct Answer
    A. 8
    Explanation
    In a two-layer lap winding, each coil spans two poles. Since there are 16 coils, there must be 8 pole pairs. Therefore, the pole pitch, which is the distance between the centers of two adjacent poles, will be 8.

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  • 26. 

    Which of the following generators have two field windings?

    • Series wound generator

    • Shunt wound generator

    • Compound wound generator

    • All of the above

    Correct Answer
    A. Compound wound generator
    Explanation
    A compound wound generator is a type of generator that has two field windings. One winding is connected in series with the armature, while the other is connected in parallel or shunt with the armature. This configuration allows the generator to have both the advantages of a series wound generator (high starting torque) and a shunt wound generator (good voltage regulation). Therefore, the correct answer is compound wound generator.

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  • 27. 

    Which of the following is also called ‘motor rule’?

    • Fleming’s right hand rule

    • Fleming’s left hand rule

    • All of the above

    • Palm rule

    Correct Answer
    A. Fleming’s left hand rule
    Explanation
    Fleming's left hand rule is also called the 'motor rule'. This rule is used to determine the direction of the force experienced by a current-carrying conductor placed in a magnetic field. By using the left hand, with the thumb representing the direction of the force, the index finger representing the magnetic field, and the middle finger representing the current, the rule helps to determine the resulting motion or force on the conductor.

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  • 28. 

     The following constitute short-circuit in the armature winding.  

    • Insulation failure between two commutator bars

    • Insulation failure between two turns of a coil

    • Two of more turns of the same coil getting grounded

    • All of the above

    Correct Answer
    A. All of the above
    Explanation
    The correct answer is "All of the above." This means that all of the given options - insulation failure between two commutator bars, insulation failure between two turns of a coil, and two or more turns of the same coil getting grounded - can cause a short-circuit in the armature winding.

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  • 29. 

    The material for commutator brushes is generally

    • mica 

    • Copper

    • Cast iron 

    • carbon

    Correct Answer
    A. carbon
    Explanation
    Carbon is the most commonly used material for commutator brushes. This is because carbon has excellent electrical conductivity, low friction, and good wear resistance. It can effectively transfer electrical current between the commutator and the stationary parts of the motor. Carbon brushes also have self-lubricating properties, which reduce friction and heat generation during operation. Additionally, carbon brushes are relatively inexpensive and easy to replace, making them a popular choice in various electrical applications.

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  • 30. 

    A  D.C. welding generator has

    • Lap winding

    • Wave moving

    • Duplex winding

    •  Any of the above

    Correct Answer
    A. Lap winding
    Explanation
    A D.C. welding generator typically uses a lap winding. Lap winding is a type of armature winding where the end of one coil overlaps with the start of the next coil. This arrangement allows for a better distribution of current and reduces the chances of short circuits. It also provides a higher voltage output and better control over the welding process. Therefore, a D.C. welding generator commonly utilizes a lap winding.

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  • 31. 

    3.In D.C. generators, the brushes on commutator remain in contact with conductors which

    • lie under south pole

    • Lie under north pole

    • Lie under interpolar region

    • are farthest from the poles

    Correct Answer
    A. Lie under interpolar region
    Explanation
    In D.C. generators, the brushes on the commutator remain in contact with conductors that lie under the interpolar region. The interpolar region is the area between the north and south poles of the generator. This region is important because it helps in reducing the sparking and improves the efficiency of the generator. By having the brushes in contact with the conductors in this region, the commutation process is improved, ensuring a smooth flow of current and reducing any potential issues with sparking or arcing.

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  • 32. 

    . When two D.C. series generators are running in parallel, an equalizer bar is used

    • To increase the speed and hence generated e.m.f.

    • To increase the series flux

    • So that two similar machines will pass approximately equal currents to the load

    • Efect of armature reaction To reduce the combined of both machines

    Correct Answer
    A. So that two similar machines will pass approximately equal currents to the load
    Explanation
    When two D.C. series generators are running in parallel, an equalizer bar is used so that two similar machines will pass approximately equal currents to the load. This is important to ensure that the load is shared equally between the generators and to prevent one generator from carrying a significantly higher load than the other. The equalizer bar allows for the adjustment of the field current in each generator, ensuring that they both contribute equally to the overall load.

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  • 33. 

    Copper brushes in D.C. machine are used

    • where low voltage and high currents are involved

    • Where high voltage and small cur-rents are involved

    • In both of the above cases

    • in none of the above cases

    Correct Answer
    A. where low voltage and high currents are involved
    Explanation
    Copper brushes in D.C. machines are used where low voltage and high currents are involved. This is because copper is an excellent conductor of electricity and can handle high currents without overheating or causing excessive resistance. Additionally, copper brushes have good wear resistance and can maintain good contact with the commutator, ensuring efficient transfer of current. Therefore, copper brushes are suitable for applications where low voltage and high currents are present, such as in electric motors or generators.

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  • 34. 

    In D.C. generators, the cause of rapid brush wear may be

    • severe sparking

    • Rough commutator surface

    • Imperfect contact

    • any of the above

    Correct Answer
    A. any of the above
    Explanation
    The cause of rapid brush wear in D.C. generators can be any of the mentioned factors: severe sparking, rough commutator surface, or imperfect contact. Severe sparking occurs when there is excessive arcing between the brushes and the commutator, leading to increased wear. A rough commutator surface can cause uneven contact with the brushes, resulting in accelerated brush wear. Imperfect contact refers to a condition where the brushes do not make proper contact with the commutator, causing friction and wear. Therefore, any of these factors can contribute to rapid brush wear in D.C. generators.

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  • 35. 

    In a commutator

    • Copper is harder than mica

    • Mica and copper are equally hard

    • Mica is harder than copper

    • None of the above

    Correct Answer
    A. Mica is harder than copper
    Explanation
    This answer suggests that mica is harder than copper. Hardness is a property that measures a material's resistance to scratching or indentation. Mica is a mineral that is known for its hardness, typically ranging from 2.5 to 4 on the Mohs scale. Copper, on the other hand, is a metal that is relatively soft and has a hardness of around 2.5 on the Mohs scale. Therefore, mica is indeed harder than copper.

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  • 36. 

    Iron losses in a D.C. machine are independent of variations in

    • Speed

    • Load

    • Voltage

    • Speed and voltage

    Correct Answer
    A. Load
    Explanation
    Iron losses in a D.C. machine are independent of variations in load. This means that the iron losses, which include hysteresis and eddy current losses, remain constant regardless of the amount of load on the machine. These losses are primarily caused by the magnetic properties of the iron core and the frequency of the magnetic field, rather than the load or the speed and voltage of the machine. Therefore, changes in load do not affect the iron losses in a D.C. machine.

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  • 37. 

    Magnetic field in a D.C. generator is produced by

    • Electromagnets

    • Permanent magnets

    • Both and

    • None of the above

    Correct Answer
    A. Electromagnets
    Explanation
    In a D.C. generator, the magnetic field is produced by electromagnets. Unlike permanent magnets, electromagnets can be turned on and off, allowing for better control and adjustment of the magnetic field strength. This is important in a generator as it enables the conversion of mechanical energy into electrical energy. Therefore, the correct answer is electromagnets.

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  • 38. 

    Copper brushes in D.C. machine are used

    • Where low voltage and high currents are involved

    • Where high voltage and small currents are involved

    • In both of the above cases

    • In none of the above cases

    Correct Answer
    A. Where low voltage and high currents are involved
    Explanation
    Copper brushes in D.C. machines are used where low voltage and high currents are involved. Copper is a good conductor of electricity and can handle high currents without overheating. By using copper brushes, the machine can efficiently transfer the high current from the power source to the rotating parts, ensuring smooth operation. Additionally, copper brushes have good wear resistance and can withstand the friction and heat generated during operation. Therefore, in applications where low voltage and high currents are present, copper brushes are the ideal choice.

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  • 39. 

    Armature reaction of an unsaturated D.C. machine is

    • crossmagnetising

    • Demagnetising

    • Magnetising 

    • none of above

    Correct Answer
    A. crossmagnetising
    Explanation
    Armature reaction of an unsaturated D.C. machine refers to the magnetic field produced by the armature current that interacts with the main magnetic field of the machine. In the case of crossmagnetising armature reaction, the armature current produces a magnetic field that is perpendicular to the main magnetic field, causing a distortion in the overall magnetic field. This can result in a reduction in the effective magnetic field strength, affecting the performance of the machine. Therefore, the correct answer is crossmagnetising.

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  • 40. 

    Iron losses in a D.C. machine are independent of variations in

    • speed 

    • Load

    • Voltage

    • speed and voltage

    Correct Answer
    A. Load
    Explanation
    Iron losses in a D.C. machine are independent of variations in load. Iron losses, also known as core losses, occur in the iron core of the machine due to hysteresis and eddy current losses. These losses are constant and do not change with variations in load. The load only affects the copper losses in the machine, which are caused by the resistance of the windings and vary with the load. Therefore, variations in load do not impact the iron losses in a D.C. machine.

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  • 41. 

    The following is (are) keyed to the shaft

    • Armature core

    • Commutator

    • Cooling fan

    • All of the above

    Correct Answer
    A. All of the above
    Explanation
    All of the listed components (armature core, commutator, and cooling fan) are keyed to the shaft. This means that they are securely attached to the shaft using a key, which is a small piece of metal that fits into a groove on both the shaft and the component. This keying ensures that the components rotate along with the shaft, allowing for efficient and synchronized operation of the motor or machine.

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  • 42. 

    Armature reaction of an unsaturated D.C. machine is

    • Cross-magnetizing

    • Demagnetizing

    • Magnetizing

    • None of above

    Correct Answer
    A. Cross-magnetizing
    Explanation
    Armature reaction refers to the magnetic effect produced by the armature current in a DC machine. In an unsaturated DC machine, the armature reaction is cross-magnetizing. This means that the magnetic field produced by the armature current interacts with the main field in such a way that it creates a magnetic field perpendicular to the main field. This cross-magnetizing effect can distort the main field and affect the performance of the machine.

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  • 43. 

    For a D.C. generator when the number of poles and the number of armature conductors is fixed, then which winding will give the higher e.m.f. ?

    • Lap winding 

    • Wave winding

    • Either of and above

    • Depends on other features of design

    Correct Answer
    A. Wave winding
    Explanation
    The wave winding will give the higher e.m.f. in a D.C. generator when the number of poles and the number of armature conductors is fixed. This is because in a wave winding, each coil spans across two poles, resulting in a higher number of parallel paths for the current to flow through. This increases the e.m.f. generated compared to a lap winding where each coil spans across only one pole. Therefore, the wave winding is more efficient in generating a higher e.m.f. in this scenario.

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  • 44. 

    Iron or magnetic losses are also called

    • Core losses

    • Field losses

    • Copper losses

    • Armature losses

    Correct Answer
    A. Core losses
    Explanation
    Core losses are also known as iron or magnetic losses. These losses occur in the core of electrical machines, such as transformers and motors, due to hysteresis and eddy current effects. Hysteresis losses are caused by the reversal of magnetization in the core material, while eddy current losses are caused by the circulating currents induced in the core. These losses result in energy dissipation in the form of heat and can significantly affect the efficiency and performance of the electrical machine. Therefore, core losses are an important consideration in the design and operation of electrical equipment.

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  • 45. 

    The mechanical losses are about _____ % of full load losses.

    • 0 to 10

    • 10 to 20

    • 20 to 30

    • 30 to 40

    Correct Answer
    A. 10 to 20
    Explanation
    The mechanical losses refer to the energy losses that occur due to friction and other mechanical factors in a system. These losses are typically a percentage of the full load losses, which are the losses that occur when the system is operating at full capacity. The correct answer, 10 to 20%, suggests that the mechanical losses are between 10% and 20% of the full load losses. This means that a significant portion of the energy losses in the system can be attributed to mechanical factors.

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  • 46. 

    In D.C. generators, lap winding is used for

    • High voltage, high current

    • Low voltage, high current

    • High voltage, low current

    • Low voltage, low current

    Correct Answer
    A. Low voltage, high current
    Explanation
    In D.C. generators, lap winding is used for low voltage, high current. Lap winding is a type of armature winding where the armature coils are connected in parallel. This configuration allows for a larger number of turns per coil, resulting in a lower voltage output. However, since the coils are connected in parallel, the current flowing through each coil is additive, leading to a higher overall current output. Therefore, lap winding is suitable for applications that require a low voltage but high current output.

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  • 47. 

    Shaft torque equals to

    • Net torque

    • Friction torque

    • Net torque + Friction torque + Torque lost

    • Net torque – (Friction torque + Torque lost)

    Correct Answer
    A. Net torque – (Friction torque + Torque lost)
    Explanation
    The correct answer is "Net torque – (Friction torque + Torque lost)". This is because the shaft torque is equal to the net torque acting on the shaft minus the sum of the friction torque and the torque lost. This equation takes into account all the forces and torques acting on the shaft and provides an accurate measure of the resulting torque.

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  • 48. 

    While applying Fleming’s right-hand rule to And the direction of induced e.m.f., the thumb points towards

    • direction of induced e.m.f.

    • Direction of flux

    • Direction of motion of the conductor if forefinger points in the direction of generated e.m.f.

    • direction of motion of conductor, if forefinger points along the lines of flux

    Correct Answer
    A. direction of motion of conductor, if forefinger points along the lines of flux
    Explanation
    When applying Fleming's right-hand rule, the thumb represents the direction of the induced e.m.f. The forefinger points in the direction of the generated e.m.f. The middle finger represents the direction of the magnetic field or lines of flux. Therefore, if the forefinger points along the lines of flux, the thumb will point in the direction of the motion of the conductor. This is because the induced e.m.f. is generated due to the relative motion between the conductor and the magnetic field.

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  • 49. 

    Equalizer rings are required in case armature is

    • Wave wound

    • Lap wound

    • Delta wound

    • Duplex wound

    Correct Answer
    A. Lap wound
    Explanation
    Equalizer rings are required in case the armature is lap wound. In a lap wound armature, the armature coils are divided into two parallel paths, with each path consisting of multiple coils connected in series. The equalizer rings are used to ensure that the current flows evenly through all the coils in each parallel path. This helps in balancing the magnetic field and prevents any imbalance in the armature current, which can lead to overheating and damage to the armature winding. Therefore, the use of equalizer rings is necessary in lap wound armatures to maintain proper functioning and prevent any potential issues.

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  • Mar 21, 2023
    Quiz Edited by
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  • Sep 20, 2018
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