# Multiple choice question for engineering

## Set 1

1. What are the applications of the small universal commutator motors?

a) industry

b) medicine

c) domestic sector

d) industry, medicine and domestic sector

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2. What type of excitation is used in the small universal commutator motors and what type of supply is provided?

a) parallel excitation, dc supply

b) series excitation, dc or ac supply

c) series excitation, ac supply

d) parallel excitation, dc supply

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3. What is the material used in the lamination of the magnetic poles of small universal commutator motor?

a) copper

b) aluminium

c) gold

d) sheet steel

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4.What is the thickness of the laminations of magnetic poles?

a) 0.3-0.5 mm

b) 0.2-0.4 mm

c) 0.35-0.5 mm

d) 0.4-0.5 mm

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5. How many type of excitations does the universal commutator motors have?

a) 1

b) 2

c) 3

d) 4

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6. The number of turns of field winding in the motor must be considerably less than the number of turns in the armature winding?

a) true

b) false

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7. What is the relation of the copper loss and brush contacts with the total loss in small dc motors?

a) copper loss and brush contacts = 2 * total loss

b) copper loss and brush contacts = 2/3 * total loss

c) copper loss and brush contacts = 1/3 * total loss

d) copper loss and brush contacts = total loss

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8. What is the relation of the copper loss and brush contacts with the total loss in universal commutator motors?

a) copper loss and brush contacts = total loss

b) copper loss and brush contacts = total loss/2

c) copper loss and brush contacts = total loss * 2

d) copper loss and brush contacts = total loss *3

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9. What is the range of the transformation ratio in the pole machines?

a) 0.05-0.1

b) 0.1-0.2

c) 0.1-0.25

d) 0.3-0.4

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10. For what outputs are the 2 pole machines made use of?

a) output > 200 W

b) output < 200 W

c) output > 300 W

d) output < 300 W

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11. What is the range of the power factor for the 4 pole motors?

a) 0.6-0.85

b) 0.75-0.95

c) 0.6-0.8

d) 0.7-0.9

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12. What is the value of the specific electric loading for the continuous duty motor type?

a) 8000-11000 A per m

b) 6000-9000 A per m

c) 12000-20000 A per m

d) 15000-25000 A per m

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13. What is the specific magnetic loading for the motors having output less than 100 W?

a) 0.25-0.30 T

b) 0.3-0.4 T

c) 1.3-1.5 T

d) 0.25-0.35 T

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14. What is the formula for the pole pitch in the universal commutator motor?

a) pole pitch = 3.14 * diameter * 2 * no. of poles

b) pole pitch = 3.14 / diameter * 2 * no. of poles

c) pole pitch = 3.14 * diameter / 2 * no. of poles

d) pole pitch = 3.14 * diameter * 2 / no. of poles

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15. What is the formula of the pole arc of the universal commutator motor?

a) pole arc = ratio of armature axial length to armature diameter * pole pitch

b) pole arc = ratio of armature axial length to armature diameter + pole pitch

c) pole arc = ratio of armature axial length to armature diameter – pole pitch

d) pole arc = ratio of armature axial length to armature diameter / pole pitch

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## Set 2

1. What is the formula for the depth and height of the yoke for stepped core?

a) depth = width of largest stamping, height = 2* width of largest stamping

b) depth = 2*width of largest stamping, height = width of largest stamping

c) depth = width of largest stamping, height = width of largest stamping

d) depth = 2*width of largest stamping, height = 2* width of largest stamping

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2.The height and the width of the single phase and three phase core type transformer equal?

a) true

b) false

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3. What is the formula for height and width of the single phase shell transformer?

a) width = 2*width of the window + 4*width of the largest stamping, height = height of the window + 2*width of the largest stamping

b) width = 2*width of the window – 4*width of the largest stamping, height = height of the window + 2*width of the largest stamping

c) width = 2*width of the window + 4*width of the largest stamping, height = height of the window – 2*width of the largest stamping

d) width = 2*width of the window – 4*width of the largest stamping, height = height of the window -2*width of the largest stamping

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4.What is the formula to calculate the number of turns/phase?

a) number of turns = secondary voltage * voltage per turn

b) number of turns = secondary voltage / voltage per turn

c) number of turns = secondary voltage + voltage per turn

d) number of turns = secondary voltage – voltage per turn

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5. What is the formula for the cross sectional area of the secondary conductor of the transformer?

a) cross sectional area = secondary current * current density

b) cross sectional area = secondary current + current density

c) cross sectional area = secondary current / current density

d) cross sectional area = secondary current – current density

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6. What is the formula for the conductor dimensions in transformer?

a) conductor dimensions = conductor width * conductor thickness + 0.5 mm

b) conductor dimensions = conductor width / conductor thickness + 0.5 mm

c) conductor dimensions = conductor width + conductor thickness + 0.5 mm

d conductor dimensions = conductor width – conductor thickness + 0.5 mm

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7. What is the formula for axial depth of low voltage winding?

a) axial depth = number of secondary turns / width of the conductor

b) axial depth = number of secondary turns * width of the conductor

c) axial depth = number of secondary turns + width of the conductor

d) axial depth = number of secondary turns – width of the conductor

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8. What is the formula for window clearance of the transformer?

a) window clearance = (height of the window + axial depth)/2

b) window clearance = (height of the window – axial depth)

c) window clearance = (height of the window – axial depth)/2

d) window clearance = (height of the window + axial depth)

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9. What is the formula to calculate the radial depth of low voltage windings?

a) radial depth of the lv windings = number of layers * radial depth of the conductors * insulation between layers

b) radial depth of the lv windings = number of layers * radial depth of the conductors – insulation between layers

c) radial depth of the lv windings = number of layers / radial depth of the conductors + insulation between layers

d) radial depth of the lv windings = number of layers * radial depth of the conductors + insulation between layers

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10. What is the formula for the inside diameter of the low voltage windings?

a) inside diameter = diameter of the circumscribing circle + pressboard thickness insulation between l.v winding and core

b) inside diameter = diameter of the circumscribing circle – pressboard thickness insulation between l.v winding and core

c) inside diameter = diameter of the circumscribing circle + 2*pressboard thickness insulation between l.v winding and core

d) inside diameter = diameter of the circumscribing circle – 2* pressboard thickness insulation between l.v winding and core

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11. What is the assumption for width of the largest stamping for the stepped core transformer?

a) 0.9*d

b) 0.71*d

c) 0.85*d

d) 0.8*d

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12. What is the range for the current density at HT side for a distribution transformer?

a) 2.4-3.5 Amp per mm^{2}

b) 2-2.5 Amp per mm^{2}

c) 1-3.5 Amp per mm^{2}

d) 2-3.5 Amp per mm^{2}

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^{2}is the range for the current density at HT side for a power transformer. 2-2.5 Amp per mm

^{2}is the range for the current density at HT side for a distribution transformer.

13. What is the relation of the height of the window with the winding height with respect to the rectangular conductors?

a) winding height = 60% * window height

b) winding height = 50% * window height

c) winding height = 80% * window height

d) winding height = 70% * window height

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14. What is the formula for number of turns/coil axially?

a) number of turns/coil axially = axial length / diameter of the insulated conductor

b) number of turns/coil axially = axial length * diameter of the insulated conductor

c) number of turns/coil axially = axial length – diameter of the insulated conductor

d) number of turns/coil axially = axial length + diameter of the insulated conductor

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15. The axial length of 16 coils = axial length of each coil * 16?

a) true

b) false

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## Set 3

1. What is specific permeance?

a) specific permeance is product of permeance of unit length and depth of field

b) specific permeance is ratio of permeance of unit length and depth of field

c) specific permeance is the permeance per unit length

d) specific permeance is the permeance per unit pole

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2. What is the formula of the specific permeance?

a) specific permeance = permeability in air * ∫small change in width + length

b) specific permeance = permeability in air * ∫small change in width/length

c) specific permeance = permeability in air * ∫small change in width * length

d) specific permeance = 1/permeability in air * ∫small change in width * length

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3. What is the assumption made in the calculation of the specific permeance?

a) voltage is kept constant

b) current is kept constant

c) mmf is kept constant

d) speed is kept constant

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4.What is the formula of the effective permeance?

a) effective permeance = effective flux/total mmf

b) effective permeance = effective flux/mmf of air gap

c) effective permeance = effective flux * total mmf

d) effective permeance = effective flux * mmf of air gap

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5. What is the formula of the flux dividing into infinitesimal parts?

a) flux dividing into infinitesimal parts = mmf producing the flux / permeance of infinitesimal part

b) flux dividing into infinitesimal parts = mmf producing the flux * permeance of infinitesimal part

c) flux dividing into infinitesimal parts = mmf producing the flux + permeance of infinitesimal part

d) flux dividing into infinitesimal parts = mmf producing the flux – permeance of infinitesimal part

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6.What is the relation between the specific permeance of a differential path and the length?

a) specific permeance of a differential path is directly proportional to the length

b) specific permeance of a differential path is indirectly proportional to the length

c) specific permeance of a differential path is directly proportional to the square of the length

d) specific permeance of a differential path is indirectly proportional to the square of the length

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7.How many factors does the value of the magnetizing current depends upon?

a) 2

b) 3

c) 4

d) 5

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8. What is the formula for the magnetizing current?

a) magnetizing current = total mmf * number of turns

b) magnetizing current = total mmf / number of turns

c) magnetizing current = total mmf + number of turns

d) magnetizing current = total mmf – number of turns

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9. What is the formula for the rms value of the magnetizing current?

a) rms value of the magnetizing current = maximum magnetizing current / peak factor

b) rms value of the magnetizing current = maximum magnetizing current * peak factor

c) rms value of the magnetizing current = maximum magnetizing current + peak factor

d) rms value of the magnetizing current = maximum magnetizing current – peak factor

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10. What is the relation of the type of winding with the flux linkage?

a) in distributed windings the flux does not link with all the turns

b) in distributed windings the flux links with all the turns

c) in concentrated windings the flux links with all the turns

d) in concentrated windings the flux does not link with all the turns

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11. What is the relation of the magnetizing current with the turns per phase?

a) magnetizing current is directly proportional to the turns per phase

b) magnetizing current is directly proportional to the square of the turns per phase

c) magnetizing current is indirectly proportional to the turns per phase

d) magnetizing current is indirectly proportional to the turns per phase

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12. The plot of the flux density distribution curve is between the interpolar axis consisting of the flux density and the angle difference between phases?

a) true

b) false

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## Set 4

1. What is the use of the wire bands of rotor?

a) used for bracing the rotor windings

b) used for circulating the current in the rotor windings

c) used for the encircling of the rotor windings

d) used for the protecting the rotor windings

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2. Where are the wire bands placed?

a) active portions of rotor conductors

b) inactive portions of rotor conductors

c) active or inactive portions of rotor conductors

d) active and inactive portions of the rotor conductors

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3. What are the factors on which the sizes of bands placed on depend?

a) length of air gap

b) method of cooling of armatures

c) length of air gap and method of cooling of armatures

d) method of cooling of armatures or length of air gap

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4.In what machines are the wire bands along the active length of windings placed?

a) dc or ac machines

b) dc and ac machines

c) dc machines

d) ac machines

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5. What is the range of the width of the each band that should not be exceeded?

a) 10-15 mm

b) 15-20 mm

c) 20-25 mm

d) 18-23 mm

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6. What is the maximum value above which the total width of the bands should not exceed?

a) 25-35% of the axial length of armature core

b) 30-35% of the axial length of armature core

c) 25-30% of the axial length of armature core

d) 35-40% of the axial length of armature core

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7. What is the formula for the breadth of the ring slot?

a) breadth of the ring slot = (number of turns in a band + 1)*diameter of band wire – 2*constant

b) breadth of the ring slot = (number of turns in a band + 1)*diameter of band wire + 2*constant

c) breadth of the ring slot = (number of turns in a band + 1)*diameter of band wire * 2*constant

d) breadth of the ring slot = (number of turns in a band + 1)*diameter of band wire / 2*constant

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8. What is the value of the constant used in the calculation of the breadth of the ring slot for the diameter of band wire < 1.5 mm?

a) 1 mm

b) 1.5 mm

c) 2 mm

d) 3 mm

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9. What is the maximum width of the bands placed on the end windings of induction machines and high speed dc machines?

a) 30 mm

b) 35 mm

c) 40 mm

d) 45 mm

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10. What is the diameter of the wire bands made of tin, steel or bronze wire?

a) 2 mm

b) 1 mm

c) 4 mm

d) 3 mm

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11. What is the function of the bands when it is placed on overhang?

a) used to reduce the centrifugal forces

b) used to increase the centrifugal forces

c) used to balance the centrifugal forces

d) used to withstand the centrifugal forces

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12. What is the function of the bands when they are distributed along the axial length of armature?

a) used to reduce the centrifugal forces

b) used to increase the centrifugal forces

c) used to decrease the centrifugal forces

d) used to withstand the centrifugal forces

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13. What is the formula of the mean diameter at the position of centre of gravity?

a) mean diameter at the position of centre of gravity = Inner diameter + diameter of stator wires

b) mean diameter at the position of centre of gravity = Inner diameter * diameter of stator wires

c) mean diameter at the position of centre of gravity = Inner diameter / diameter of stator wires

d) mean diameter at the position of centre of gravity = Inner diameter – diameter of stator wires

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14. What is the value of permissible stress for bronze wire for the diameter of branding wire of 1 mm?

a) 350 NM per m^{2}

b) 250 NM per m^{2}

c) 300 NM per m^{2}

d) 450 NM per m^{2}

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^{2}.

15. What is the value of permissible stress for steel wire for the diameter of branding wire of 0.5-1.2 mm?

a) 570 NM per m^{2}

b) 600 NM per m^{2}

c) 650 NM per m^{2}

d) 700 NM per m^{2}

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^{2}. The value of permissible stress for steel wire for the diameter of branding wire of 1.5-2 mm is 570 NM per m

^{2}.

## Set 5

1. How many factors does the design of armature of synchronous machines depend upon?

a) 2

b) 4

c) 3

d) 5

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2. When are the double layer bar windings made use of during the armature design?

a) large values of flux per pole and small number of turns per phase

b) large values of flux per pole and large number of turns per phase

c) small values of flux per pole and small number of turns per phase

d) small values of flux per pole and large number of turns per phase

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3. Which type of machines have a large number of poles per phase?

a) high voltage machines and machines with high value of flux per pole

b) high voltage machines and machines with small value of flux per pole

c) small voltage machines and machines with high value of flux per pole

d) small voltage machines and machines with low value of flux per pole

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4. Which among the following makes double layer windings advantageous than the single layer windings?

a) ease in the manufacture of coils and lower cost of winding

b) less number of coils are required as spare in the case of winding repairs

c) fractional slot windings can be employed

d) ease in the manufacture of coils and lower cost of winding, fractional slot windings can be employed, less number of coils are required as spare in the case of winding repairs

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5. The single layer windings have higher efficiency and quieter operation because of narrow slot openings?

a) true

b) false

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6. When is the double layer bar or wave windings made use of?

a) when single turns coils are necessary as with turbo alternators and unipolar low voltage machines

b) when single turns coils are necessary as with turbo alternators and bipolar low voltage machines

c) when single turns coils are necessary as with turbo alternators and multipolar low voltage machines

d) when double turns coils are necessary as with turbo alternators and unipolar low voltage machines

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7. How many factors are related in the selection of the armature slots?

a) 5

b) 6

c) 7

d) 4

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8. How is the number of armature slots associated with the armature windings?

a) number of slots should be such that unbalanced winding is obtained

b) number of slots should be such that balanced winding is obtained

c) number of slots should be so low as possible

d) number of slots should be high as possible

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9. How is the number of armature slots associated with the cost factor?

a) small number of slots leads to less cost

b) small number of slots leads to high cost

c) large number of slots leads to high cost

d) large number of slots leads to low cost

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10. How is the number of armature slots associated with the hotspot temperature?

a) small number of slots leads to less hotspot temperature

b) small number of slots leads to high hotspot temperature

c) large number of slots leads to high hotspot temperature

d) large number of slots leads to low hotspot temperature

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11. How is the number of armature slots associated with the leakage reactance?

a) small number of slots leads to less leakage reactance

b) small number of slots leads to high leakage reactance

c) large number of slots leads to high leakage reactance

d) large number of slots leads to low leakage reactance

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12. How is the number of armature slots associated with the tooth ripples?

a) tooth ripples are increased, if the number of slots are increased

b) tooth ripples are decreased, if the number of slots are increased

c) tooth ripples are increased, if the number of slots are decreased

d) tooth ripples are decreased, if the number of slots are decreased

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13. How is the number of armature slots associated with the flux densities in iron?

a) tooth ripples are increased, if the number of slots are increased

b) tooth ripples are decreased, if the number of slots are increased

c) tooth ripples are increased, if the number of slots are decreased

d) tooth ripples are decreased, if the number of slots are decreased

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14.The value of slot pitch depends upon the voltage of the machine?

a) true

b) false

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15. What is the value of the slot pitch for the low voltage machines?

a) slot pitch < 25 mm

b) slot pitch = 25 mm

c) slot pitch less than equal to 25 mm

d) slot pitch greater than equal to 25 mm