# Multiple choice question for engineering

## Set 1

1.How many types are the current transformers classified into?

a) 2

b) 3

c) 4

d) 5

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2. What is the wound type current transformer?

a) primary winding having one full turn wound on core

b) primary winding having more than one full turn wound on core

c) secondary winding having one full turn wound on core

d) secondary winding having more than one full turn wound on core

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3. What is the bar type current transformer?

a) primary winding consists of a rod of suitable size and material

b) primary winding consists of a bar of suitable size and material

c) secondary winding consists of a rod of suitable size and material

d) secondary winding consists of a bar of suitable size and material

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4.How many commonly used shapes of current transformer are present?

a) 1

b) 2

c) 3

d) 4

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5. What material is made use of for the lamination in the current transformer?

a) cold rolled steels

b) hot rolled steels

c) copper

d) hot iron

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6. What is the insulation material used in the current transformer?

a) elephantide

b) presspahn

c) elephantide and presspahn

d) elephantide or presspahn

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7. What is the additional usage of the presspahn material used as insulation material?

a) lamination

b) to reduce the losses

c) to protect secondary winding conductor from mechanical damage

d) to protect secondary winding conductor from electrical damage

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8. What is the other name of the ring type current transformer?

a) brush transformer

b) cloud transformer

c) circular transformer

d) bushing transformer

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9.How many faces are present in the split core current transformer?

a) 2

b) 3

c) 4

d) 5

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10. The current transformers are assembled on to the secondary conductors “on site” for either permanent or temporary duty?

a) true

b) false

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11. What is the insulation material on the primary conductor?

a) bakelized paper tube

b) resin

c) bakelized paper tube and resin

d) bakelized paper tube or resin

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12. How is the reluctance of the interleaved corner related with the magnetizing current?

a) reluctance of the interleaved corner is directly proportional to the magnetizing current

b) reluctance of the interleaved corner is indirectly proportional to the magnetizing current

c) reluctance of the interleaved corner is directly proportional to the square of the magnetizing current

d) reluctance of the interleaved corner is indirectly proportional to the square of the magnetizing current

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13. To reduce the peak voltage between layers, the secondary winding is being sectionalized?

a) true

b) false

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## Set 2

1. How many type of armature windings are present in the DC machine armature?

a) 2

b) 3

c) 4

d) 5

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2. Which factor determines the difference between the types of armature windings?

a) brush connection

b) slip ring connection

c) commutator connection

d) pole connection

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3. What is the meaning of pole pitch?

a) type of armature slot

b) number of armature slots/pole

c) number of poles/armature slot

d) number of poles/number of armature slots

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4. A 4 pole DC machine has 36 number of armature conductors. What is the pole pitch ?

a) 9

b) 1/9

c) 92

d) 1/92

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5. The choosing of the slot values for armature depends on the type of windings?

a) true

b) false

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6. What is the condition for choosing the armature current/parallel path in armature design?

a) > 200 ampere for both lap and wave windings

b) >200 ampere for lap winding, <200 ampere for wave winding

c) < 200 ampere for both lap and wave windings

d) <200 ampere for lap winding, >200 ampere for wave winding

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7. What is the range of armature slot pitch in the armature slot design?

a) 20mm – 25mm

b) 25mm – 35mm

c) 30mm – 35mm

d) > 35mm

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8. For a DC machine, the armature slot pitch is 35mm and the diameter is 0.2m. What is the number of armature slots for the machine?

a) 17

b) 18

c) 19

d) 20

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9. What is the formula to reduce flux pulsations?

a) armature slot/number of poles = integer

b) armature slot/number of poles = integer + 0.5

c) armature slot/number of poles = integer – 0.5

d) armature slot/number of poles = integer +-0.5

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10. The number of coils chosen should be minimum in number?

a) true

b) false

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11. What should be the range of the integer value while calculating the formula to reduce the flux pulsations?

a) 8-14

b) 9-15

c) 9-16

d) 9-17

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12. What is ‘Z/Sa’ calculation during design of armatures?

a) armature poles/slots

b) armature conductors/slots

c) armature slots/poles

d) armature slots/conductors

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13. What is the formula for calculating the minimum number of coils?

a) Cmin = Voltage

b) Cmin = Voltage/5

c) Cmin = Voltage/10

d) Cmin = Voltage/15

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14. Given Z=228 conductors, number of coils C=38 for a DC machine. What is the turns/coils ratio?

a) 4

b) 3

c) 7

d) 3

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15. For a DC generator, given the load current is 510 ampere, field current is 1.4 ampere. What is the value of armature current?

a) 508.6 ampere

b) 714 ampere

c) 511.4 ampere

d) 364.28 ampere

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## Set 3

1. What is a commutator in DC machines?

a) electrical device which reverses the current direction between the rotor and external circuit

b) mechanical device which reverses the current direction between the rotor and external circuit

c) electrical device which allows the current flow between the rotor and external circuit

d) mechanical device which allows the current flow between the rotor and external circuit

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2. What is the use of brushes in DC machines?

a) to connect the parts of the machine to the external circuit

b) to conduct current between moving parts

c) to conduct current between stationary wires and moving parts

d) used for smooth conduction of current

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3. Which material is commonly used in brushes?

a) copper

b) carbon

c) silicon

d) steel

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4. What is the total number of design steps available for the commutators in DC machines?

a) 4

b) 3

c) 2

d) 5

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5. What is the total number of design steps for the brushes in DC machines?

a) 4

b) 3

c) 5

d) 6

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6. What factor does the diameter of the commutator depends on?

a) length of the commutator

b) speed of the commutator

c) peripheral speed of the commutator

d) opening of the commutator

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7. For a DC machine, given Diameter of the commutator= 0.48 m, Speed = 600 rpm. What is the voltage across the commutator?

a) 15 V

b) 15.5 V

c) 15.2 V

d) 15.1 V

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8. What is the other name for commutator segment pitch of DC machines?

a) width of the commutator

b) length of the commutator

c) breadth of the commutator

d) height of the commutator

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9. What is the formula for finding out the width of the commutator of the DC machines?

a) width of the commutator = 3.14*(Diameter of the commutator)

b) width of the commutator = 3.14*(Diameter of the commutator)*(Number of armature coils)

c) width of the commutator = 3.14*(Diameter of the commutator) / (Number of armature coils)

d) width of the commutator = Number of armature coils / 3.14*(Diameter of the commutator)

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10. The diameter of the commutator should be 0.2-0.4 times the main diameter for a good design?

a) true

b) false

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11. What should be the range for the width of the commutator in a good design?

a) < 4 mm

b) > 4 mm

c) 3-4 mm

d) < 3 mm

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12. The design of commutator and the brushes of DC machines are interconnected?

a) true

b) false

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13. What is the formula for calculation of brush current of DC machine for wave winding?

a) brush Current = 2*(Armature Current) / P

b) brush Current = (Armature Current) / P

c) brush Current = Armature Current

d) brush Current = P/2*(Armature Current)

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14. What is the formula for brush contact loss of DC machines?

a) brush contact loss = armature current + brush contact voltage

b) brush contact loss = armature current – brush contact voltage

c) brush contact loss = armature current * brush contact voltage

d) brush contact loss = (armature current + brush contact voltage) / 2

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15. What is the formula for total commutator loss for DC machine?

a) brush contact loss + brush friction loss

b) brush contact loss – brush friction loss

c) brush contact loss * brush friction loss

d) brush contact loss / brush friction loss

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## Set 4

1. What is stacking factor?

a) the allowance made for the power loss

b) the allowance made for the space loss between laminations

c) the allowance made for the heat loss between laminations

d) the allowance made for the power loss between laminations

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2. What is utilization factor?

a) utilization factor= cross sectional area + gross area of the core

b) utilization factor= cross sectional area – gross area of the core

c) utilization factor= cross sectional area * gross area of the core

d) utilization factor= cross sectional area / gross area of the core

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3. What is the relationship between utilization factor and the number of core steps?

a) utilization factor is directly proportional to the number of core steps

b) utilization factor is indirectly proportional to the number of core steps

c) utilization factor is indirectly proportional to the square of number of core steps

d) utilization factor is directly proportional to the square of number of core steps

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4. What is the optimum number of steps for small and large transformers?

a) 5,10

b) 10,15

c) 6,15

d) 1,10

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5. What happens if the utilization factor gets improved?

a) core area increases and the volt/turns decreases

b) core area increases and the volt/turns increases

c) core area decreases and the volt/turn decreases

d) core area decreases and the volt/turn increases

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6. How many types of cores are available for core type of transformer?

a) 2

b) 3

c) 4

d) 5

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7. What type of core section is used for shell type transformer?

a) rectangular

b) square

c) stepped

d) cruciform

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8. What is the range of the ratio of depth to width of core in rectangular core?

a) 1-2

b) 1.5-2.5

c) 1.4-2

d) 1.5-2

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9. When is square and stepped cores used?

a) when circular coils are required for low voltage distribution

b) when rectangular coils are required for low voltage distribution

c) when circular coils are required for high voltage distribution

d) when rectangular coils are required for high voltage distribution

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10. Circular coils are preferred because of their electrical characteristics?

a) true

b) false

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11. What is the ratio of the net core area to the area of the circumscribing circle in square cores?

a) 0.58

b) 0.64

c) 0.70

d) 0.80

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12. The laminations are manufactured in standard size to minimize the wastage of steel during punching of laminations?

a) true

b) false

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13. What is the value of ratio of gross core area to the area of circumscribing circle in stepped cores?

a) 0.71

b) 0.79

c) 0.89

d) 0.91

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14. What is the net core area for three stepped transformers?

a) 0.45

b) 0.56

c) 0.6

d) 0.62

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15. What is the relationship between the number of steps to the area of circumscribing circle?

a) number of steps is directly proportional to the area of the circumscribing circle

b) number of steps is indirectly proportional to the area of the circumscribing circle

c) number of steps is directly proportional to square of the area of the circumscribing circle

d) number of steps is indirectly proportional to square of the area of the circumscribing circle

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## Set 5

1. How many design factors are involved in the CAD design of DC motors?

a) 5

b) 6

c) 7

d) 4

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2. What is the symbol used for the terminal voltage in dc motor design?

a) V

b) Vs

c) Vt

d) Tv

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3. What is the symbol used for the slot per pole arc in dc motor design?

a) sppa

b) spa

c) ssa

d) sp

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4. What is the symbol used for the flux density produced in the pole body of dc motor design?

a) fp

b) fdp

c) fyp

d) fypd

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5. What is the symbol used for the total mmf required for the teeth?

a) AT

b) ATt

c) Tm

d) Tmt

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6. What is the symbol used for the pitch of commutator segments in the dc motor?

a) Pc

b) Pcs

c) BETAc

d) Ret

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7. How many design steps are involved in the design of main dimensions of synchronous machine?

a) 10

b) 9

c) 7

d) 8

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8. What is the number of design steps involved in the length of air gap?

a) 7

b) 8

c) 9

d) 10

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9. What is the number of design steps involved in the stator?

a) 6

b) 7

c) 8

d) 9

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10. What is the number of design steps involved in the number of slots?

a) 4

b) 5

c) 6

d) 7

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11. What is the symbol used for the armature mmf per pole?

a) AT

b) ATM

c) Amp

d) ATa

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12. What is the symbol used for the width of the ventilating duct?

a) Wv

b) Nw

c) Wvd

d) Wvds