# Multiple choice question for engineering

## Set 1

1. What is the consideration for the determination of the diameter of shaft?

a) stiffness

b) voltage

c) current

d) rigidity

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2. What is the meaning of stiffness?

a) ability to transmit the power

b) ability to withstand the weight of the rotor

c) ability to withstand unbalanced magnetic pull

d) ability to withstand the weight of rotor and unbalanced magnetic pull

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3. What should be the first property of the shaft design?

a) the shaft design should be such that the shaft must have enough corrosion resistance

b) the shaft design should be such that the shaft must have enough mechanical strength

c) the shaft design should be such that the shaft has enough tensile strength

d) the shaft design should be able to withstand the voltage fluctuations

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4. What is the second property of the shaft design?

a) the shaft design should be such that it has high rigidity

b) the shaft design should be such that it should have high tensile strength

c) the shaft design should be such that it should have high corrosion resistance

d) the shaft design should be such that it should withstand voltage fluctuations

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5. The critical speeds of rotation should be different from running speed of machine?

a) true

b) false

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6. What is the formula of the diameter of the shaft?

a) diameter of the shaft = 5.5 + (output in watt/rps)1/3 mm

b) diameter of the shaft = 5.5 – (output in watt/rps)1/3 mm

c) diameter of the shaft = 5.5 * (output in watt/rps)1/3 mm

d) diameter of the shaft = 5.5 / (output in watt/rps)1/3 mm

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7. What is the relation of the diameter of the shaft in the bearings to the diameter under the armature?

a) diameter of the shaft is very much greater than the diameter under the armature

b) diameter of the shaft is greater than the diameter under the armature

c) diameter of the shaft is equal to the diameter under the armature

d) diameter of the shaft is lesser than the diameter under the armature

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8. What happens when the diameter under armature is 150 mm or above?

a) diameter of the shaft in bearing is 100 mm smaller than the maximum diameter

b) diameter of the shaft in bearing is 90 mm smaller than the maximum diameter.

c) diameter of the shaft in bearing is 70 mm smaller than the maximum diameter.

d) diameter of the shaft in bearing is 50 mm smaller than the maximum diameter.

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9. What happens in the case of the small shafts?

a) the diameter in the bearings should be about 1/3 of the maximum diameter

b) the diameter in the bearing should be about 2/3 of the maximum diameter

c) the diameter in the bearing should be about 2/5 of the maximum diameter

d) the diameter in the bearing should be about 1/5 of the maximum diameter

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## Set 2

1. How is he reluctance motor with respect to synchronous motor and are the field windings?

a) small synchronous motor with field windings

b) small synchronous motor without field windings

c) large synchronous motor with field windings

d) large synchronous motor without field windings

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2. Why is the three phase reluctance motor preferred over single phase reluctance motor?

a) single phase reluctance motors have the phenomenon of hunting

b) single phase reluctance motors have the phenomenon of over voltage

c) single phase reluctance motors have high losses

d) single phase reluctance motors have low output

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3. What is the relation of the input voltage with the magnetic flux?

a) if the input voltage is constant, the magnetic flux increases

b) if the input voltage is constant, the magnetic flux decreases

c) if the input voltage is constant, the magnetic flux is constant

d) if the input voltage is constant, the magnetic flux is zero

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4.What is the power factor in the reluctance motor and the range of efficiency?

a) leading power factor, 60-75%

b) lagging power factor, 50-75%

c) zero power factor, 55-80%

d) lagging power factor, 55-75%

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5. What is the angle at which the electromagnetic torque is maximum?

a) 300

b) 450

c) 600

d) 900

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6. What is the range of the ratio of the direct axis reactance to the quadrature axis reactance?

a) 1.5-2.3

b) 1.6-2.7

c) 1.6-2.2

d) 1.2-2.0

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7. How many design dimension are present in the design of the small reluctance motor?

a) 3

b) 4

c) 5

d) 6

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8. What is the range of the constant used in the calculation of the active power of reluctance motor?

a) 0.3-0.4

b) 0.35-0.55

c) 0.40-0.50

d) 0.35-0.60

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9. How many steps are present in the calculation of the determination of main dimensions?

a) 5

b) 4

c) 3

d) 2

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10. How many steps are present in the calculation of the design of stator windings?

a) 10

b) 11

c) 9

d) 12

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11. How many steps are present in the calculation of the design of rotor of reluctance motors?

a) 4

b) 5

c) 3

d) 2

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12. How many steps are involved in the design of performance parameters?

a) 6

b) 5

c) 7

d) 8

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13. How many design steps are involved in the determination of the losses and efficiency?

a) 2

b) 3

c) 4

d) 5

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14. What is the formula for the slot pitch factor in design of rotors?

a) slot pitch factor = 3.14*rotor diameter*number of rotor slots

b) slot pitch factor = 3.14/rotor diameter*number of rotor slots

c) slot pitch factor = 3.14*rotor diameter/number of rotor slots

d) slot pitch factor = 1/3.14*rotor diameter*number of rotor slots

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15. The active resistance of the stator winding is calculated at the temperature of 450 C?

a) true

b) false

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## Set 3

1. What type is the stator windings of the single phase induction motor?

a) hollow

b) cylindrical

c) concentric

d) rectangular

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2. How many coils are present in the stator windings?

a) 2

b) 3

c) 2 or more

d) 3 or more

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3. How much of the total slots are used for the reduction of the mmf wave harmonics?

a) 60%

b) 65%

c) 70%

d) 80%

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4.How can the small single phase motor reduce the harmonics still much further?

a) removing the winding

b) insulating the winding

c) grading the winding

d) shading the winding

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5. What is the formula for the mean pitch factor?

a) mean pitch factor = pitch factor of each coil per pole group + turns in the coil / total number of turns

b) mean pitch factor = pitch factor of each coil per pole group / turns in the coil * total number of turns

c) mean pitch factor = pitch factor of each coil per pole group * turns in the coil * total number of turns

d) mean pitch factor = pitch factor of each coil per pole group * turns in the coil / total number of turns

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6. What is the range of the winding factor for the usual windings distribution?

a) 0.70-0.80

b) 0.75-0.85

c) 0.70-0.85

d) 0.70-0.75

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7. What is the formula of the maximum flux in the running winding?

a) maximum flux = flux * pole

b) maximum flux = flux/pole

c) maximum flux = flux / turns

d) maximum flux = flux * turns

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8. What is the value of the stator induced voltage with respect to the supply voltage?

a) stator induced voltage = 95% of supply voltage

b) stator induced voltage = 90% of supply voltage

c) stator induced voltage = 85% of supply voltage

d) stator induced voltage = 80% of supply voltage

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9. How many design data are present in the design of the stator?

a) 6

b) 7

c) 8

d) 9

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10. What is the range of the current density for the open type motors split phase, capacitor and repulsion start motors?

a) 4-5 A per mm^{2}

b) 3-4 A per mm^{2}

c) 2-4 A per mm^{2}

d) 1-4 A per mm^{2}

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^{2}. The maximum value of the current density for the open type motors split phase, capacitor and repulsion start motors is 4 A per mm

^{2}.

11. What is the relation of the number of slots with the leakage reactance?

a) small number of slots, high leakage reactance

b) large number of slots, high leakage reactance

c) large number of slots, small leakage reactance

d) small number of slots, small leakage reactance

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12. What is the formula for the area required for the insulated conductors?

a) area required for the insulated conductors = total number of conductors per slot * 0.785 / diameter of insulated conductor2

b) area required for the insulated conductors = total number of conductors per slot / 0.785 * diameter of insulated conductor2

c) area required for the insulated conductors = total number of conductors per slot * 0.785 * diameter of insulated conductor2

d) area required for the insulated conductors = 1/total number of conductors per slot * 0.785 * diameter of insulated conductor2

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13. The flux density of the high torque machines is 1.8 weber per m^{2}?

a) true

b) false

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^{2}.

14. The flux density of the stator core should not exceed 1.3 weber per m^{2}?

a) true

b) false

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^{2}.

15. What is the formula for the flux density in stator core?

a) flux density in stator core = maximum flux / length of the iron * depth of stator core

b) flux density in stator core = maximum flux * length of the iron * depth of stator core

c) flux density in stator core = maximum flux / 2 *length of the iron * depth of stator core

d) flux density in stator core = maximum flux * length of the iron / depth of stator core

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## Set 4

1. How many design steps are present in the design of PMDC motors?

a) 8

b) 9

c) 10

d) 11

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2. What happens to the armature diameter and the volume of air gap and magnet when the angle is lower in value?

a) volume of air gap and magnet increases, armature diameter increases

b) volume of air gap and magnet increases, armature diameter decreases

c) volume of air gap and magnet decreases, armature diameter decreases

d) volume of air gap and magnet decreases, armature diameter increases

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3. What should be the range of the product of the magnetic field and magnetic flux density?

a) 4-4.5 * 106

b) 4-4.3 * 106

c) 4.3-4.6 * 106

d) 4.2-4.5 * 106

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4.What should be the minimum value of the ratio of the magnetic to electric loading?

a) 40

b) 30

c) 50

d) 60

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5. What is the formula for the area of the magnet in the design of PMDC motors?

a) area of magnet = flux * 4.95 * residual flux density

b) area of magnet = flux / 4.95 * residual flux density

c) area of magnet = flux * 4.95 / residual flux density

d) area of magnet = 1/flux * 4.95 * residual flux density

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6. What is the range of length of the magnet in the PMDC motors?

a) 2.5-4 cm

b) 2-3 cm

c) 2.5-3 cm

d) 1.5-4 cm

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7. What is the formula of the length of the magnet?

a) length of the magnet = sum of the volume of air gap and magnet * Area of the magnet + 0.06

b) length of the magnet = sum of the volume of air gap and magnet / Area of the magnet + 0.06

c) length of the magnet = sum of the volume of air gap and magnet / Area of the magnet – 0.06

d) length of the magnet = sum of the volume of air gap and magnet * Area of the magnet – 0.06

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8. What is the relation between the flux and the no local speed?

a) flux is directly proportional to the no local speed

b) flux is indirectly proportional to the no local speed

c) flux is directly proportional to the square of the no local speed

d) flux is indirectly proportional to the square of the no local speed

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9.What is the formula of the number of turns per coil?

a) number of turns per coil = number of conductors/2*coils/slot*number of armature teeth

b) number of turns per coil = number of conductors*2*coils/slot*number of armature teeth

c) number of turns per coil = number of conductors*2*coils/slot/number of armature teeth

d) number of turns per coil = number of conductors/2*coils/slot/number of armature teeth

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10. What is the formula for the armature resistance?

a) armature resistance = running armature resistance / 1.0 to 1.0

b) armature resistance = running armature resistance * 1.3 to 1.5

c) armature resistance = running armature resistance * 1.4 to 1.5

d) armature resistance = running armature resistance / 1.3 to 1.3

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11. What is the relation between axial dimension and the area of the magnet?

a) area of the magnet is directly proportional to the axial dimension

b) area of the magnet is indirectly proportional to the axial dimension

c) area of the magnet is directly proportional to the square of the axial dimension

d) area of the magnet is indirectly proportional to the square of the axial dimension

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12. What is the relation of the wire cross-section with respect to the armature resistance?

a) wire section is directly proportional to the armature resistance

b) wire section is indirectly proportional to the armature resistance

c) wire section is directly proportional to the square of the armature resistance

d) wire section is indirectly proportional to the square of the armature resistance

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13. The radial thickness of the joke directly proportional to the flux?

a) true

b) false

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14.The radial thickness of the joke is directly proportional to the length of the stator slots?

a) true

b) false

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15. What is the formula of the length of the stator slots?

a) length of the stator slots = 2 * perimeter of one magnet

b) length of the stator slots = 1/2 * perimeter of one magnet

c) length of the stator slots = 1/3 * perimeter of one magnet

d) length of the stator slots = 3 * perimeter of one magnet

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## Set 5

1. What is the usage of the tanks with tubes?

a) if the temperature rise with plain tank is very low

b) if the temperature rise with plain tank is very high

c) if the temperature rise is zero

d) if the temperature rise with plain tank exceeds the specific limits

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2. What is the relation of the provision of tubes with respect to dissipation of heat?

a) the provision of tubes is directly proportional to the dissipation of heat

b) the provision of tubes is indirectly proportional to the dissipation of heat

c) the provision of tubes is directly proportional to square of the dissipation of heat

d) the provision of tubes is indirectly proportional to square of the dissipation of heat

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3. What is the relation of the transformer surface with respect to dissipation of heat?

a) transformer surface has no relation with respect to dissipation of heat

b) transformer surface has minor changes with respect to dissipation of heat

c) transformer surface has major changes with respect to dissipation of heat

d) transformer surface has no change with respect to dissipation of heat

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4.How is the circulation of oil improved in tanks with tubes?

a) it can be improved by using dissipating heat

b) it can be improved by using more effective air circulation

c) it can be improved by using more effect power flow

d) it can be improved by using more effective heads of pressure

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5. An addition of 35 per cent should be made to tube area of the transformers?

a) true

b) false

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6. What is the loss dissipated by tubes by convection, given area of the tubes = 3.5?

a) 12.3 W per 0c

b) 2.51 W per 0c

c) 5.3 W per 0c

d) 30.8 W per 0c

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7. What is the formula for temperature rise with tubes?

a) temperature rise with tubes = total loss / dissipating surface*(12.5 + 8.8x)

b) temperature rise with tubes = total loss * dissipating surface*(12.5 + 8.8x)

c) temperature rise with tubes = total loss / dissipating surface / (12.5 + 8.8x)

d) temperature rise with tubes = total loss + dissipating surface*(12.5 + 8.8x)

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8. What is the formula for number of tubes?

a) number of tubes = (1/ 8 * area of each tube) * (total loss / temperature rise with tubes – 12.5 * dissipating surface)

b) number of tubes = (1* 8 * area of each tube) * (total loss / temperature rise with tubes – 12.5 * dissipating surface)

c) number of tubes = (1/ 8 * area of each tube) / (total loss / temperature rise with tubes – 12.5 * dissipating surface)

d) number of tubes = (1/ 8 * area of each tube) + (total loss / temperature rise with tubes – 12.5 * dissipating surface)

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9. What is the range of the diameter of the tubes used?

a) 50-60 mm

b) 60-70 mm

c) 70-80 mm

d) 50-70 mm

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10. Elliptical tubes with pressed radiators are increasingly been used?

a) true

b) false

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11. What is the formula for width of the tank for single phase transformers used?

a) width of tank = 2*distance between adjacent limbs + external diameter of h.v windings + 2*clearance between h.v windings and tank

b) width of tank = distance between adjacent limbs + external diameter of h.v windings + 2*clearance between h.v windings and tank

c) width of tank = 2*distance between adjacent limbs * external diameter of h.v windings + 2*clearance between h.v windings and tank

d) width of tank = distance between adjacent limbs * external diameter of h.v windings + 2*clearance between h.v windings and tank

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12. What is the formula for the length of the tank?

a) length of the tank = external diameter of h.v winding + clearance on each side between the winding and tank along the width

b) length of the tank = external diameter of h.v winding * clearance on each side between the winding and tank along the width

c) length of the tank = external diameter of h.v winding + 2*clearance on each side between the winding and tank along the width

d) length of the tank = external diameter of h.v winding / 2*clearance on each side between the winding and tank along the width

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13. What is the formula for height of transformer tank?

a) height of transformer tank = Height of transformer frame + clearance height between the assembled transformer and tank

b) height of transformer tank = Height of transformer frame * clearance height between the assembled transformer and tank

c) height of transformer tank = Height of transformer frame / clearance height between the assembled transformer and tank

d) height of transformer tank = Height of transformer frame – clearance height between the assembled transformer and tank

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14. What is the rating of the transformer for the voltage of about 11 kV?

a) 1000-2000 kVA

b) 100-3000 kVA

c) 1000-5000 kVA

d) 100-500 kVA

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15. What is the rating of the transformer for the voltage of above 11 kV upto 33 kV?

a) 1000-5000 kVA

b) less than 1000 kVA

c) above 1000 kVA

d) 100-500 kVA