# Multiple choice question for engineering

## Set 1

1. What is the rotor windings for wound rotor motors?

a) single phase windings

b) double phase windings

c) three phase windings

d) concentrated phase windings

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2.How should the number of slots be in the case of fractional slot windings?

a) multiples of slots

b) multiple of phases

c) multiple of phases and pair of poles

d) multiples of pair of poles

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3.How many types of design of wound rotors are available?

a) 2

b) 3

c) 4

d) 5

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4. What should be done to keep the rotor voltage to an acceptable level?

a) rotor to stator turns must be properly adjusted

b) stator to rotor turns must be properly adjusted

c) stator turns must be adjusted

d) rotor turns must be adjusted

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5. The rotor voltage on open circuit between slip rings should not exceed 500 V for small machines?

a) true

b) false

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6. How should the rotor voltage be with respect to the high voltage and large machines?

a) low

b) moderate

c) high

d) very high

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7. What is the range of the rotor voltage for the large machines?

a) 1000-1500 V

b) 1000-1750 V

c) 500-1500 V

d) 1000-2000 V

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8. What is the formula for rotor turns per phase?

a) rotor turns per phase = (winding factor for stator/winding factor for rotor) * (Rotor voltage per phase/Stator voltage per phase) * Number of turns per phase for stator

b) rotor turns per phase = (winding factor for stator/winding factor for rotor) / (Rotor voltage per phase/Stator voltage per phase) * Number of turns per phase for stator

c) rotor turns per phase = (winding factor for stator/winding factor for rotor) * (Rotor voltage per phase/Stator voltage per phase) / Number of turns per phase for stator

d) rotor turns per phase = (winding factor for stator/winding factor for rotor) / (Rotor voltage per phase/Stator voltage per phase) / Number of turns per phase for stator

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9. What is the formula for the full load rotor mmf?

a) 65% of stator mmf

b) 75% of stator mmf

c) 85% of stator mmf

d) 90% of stator mmf

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10. The value of the current density of rotor is chosen almost equal to that in the stator?

a) true

b) false

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11. What type of conductor is chosen for the small motors?

a) round

b) bar

c) skewed

d) rectangular

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12. What type of winding is made use of for the small motors?

a) mush windings

b) cross windings

c) interconnected windings

d) rounded windings

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13. What type of winding is made use of for the large motors?

a) mush windings

b) bar type windings

c) cross windings

d) rounded windings

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## Set 2

1. How many factors influence the power factor of an induction motor?

a) 3

b) 2

c) 1

d) 4

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2. What is the relation between the magnetizing current and power factor?

a) magnetizing current is directly proportional to the power factor

b) magnetizing current is indirectly proportional to the power factor

c) magnetizing current is directly proportional to the square of the power factor

d) magnetizing current is indirectly proportional to the square of the power factor

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3. What is the relation between the leakage current and power factor?

a) leakage current is directly proportional to the power factor

b) leakage current is indirectly proportional to the power factor

c) leakage current is directly proportional to the square of the power factor

d) leakage current is indirectly proportional to the square of the power factor

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4. What is the formula for dispersion coefficient?

a) dispersion coefficient = magnetizing current / ideal short circuit current

b) dispersion coefficient = magnetizing current * ideal short circuit current

c) dispersion coefficient = magnetizing current + ideal short circuit current

d) dispersion coefficient = magnetizing current – ideal short circuit current

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5. What is the formula for dispersion coefficient?

a) dispersion coefficient = 0.838 * 106 * 3.14 / air gap length * effective specific permeance / pole pitch * (window space factor)2 * number of slots per pole per phase

b) dispersion coefficient = 0.838 * 106 * 3.14 * air gap length / effective specific permeance / pole pitch * (window space factor)2 * number of slots per pole per phase

c) dispersion coefficient = 0.838 * 106 * 3.14 * air gap length * effective specific permeance * pole pitch * (window space factor)2 * number of slots per pole per phase

d) dispersion coefficient = 0.838 * 106 * 3.14 * air gap length * effective specific permeance / pole pitch * (window space factor)2 * number of slots per pole per phase

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6. The increase in number of poles, the dispersion coefficient increases and this gives a low power factor?

a) true

b) false

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7. What is the relation between the number of poles and pole pitch with power factor?

a) number of poles increases, pole pitch increases, bad power factor

b) number of poles increases, pole pitch decreases, good power factor

c) number of poles increases, pole pitch decreases, good power factor

d) number of poles increases, pole pitch increases, bad power factor

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8. What is the relation between the power factor and the air gap length?

a) small air gap length, dispersion coefficient increases, good power factor

b) small air gap length, dispersion coefficient decreases, bad power factor

c) small air gap length, dispersion coefficient increases, bad power factor

d) small air gap length, dispersion coefficient decreases, good power factor

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9. What is the relation between the dispersion coefficient and maximum power factor?

a) dispersion coefficient is directly proportional to the power factor

b) dispersion coefficient is indirectly proportional to the power factor

c) dispersion coefficient is directly proportional to the square of the power factor

d) dispersion coefficient is indirectly proportional to the square of the power factor

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10. What is the value of the no. of poles for obtaining a dispersion coefficient = 0.5?

a) 5

b) 7

c) 10

d) 6

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11. What is the relation between the overload capacity and dispersion coefficient?

a) overload capacity is directly proportional to the dispersion coefficient

b) overload capacity is indirectly proportional to the dispersion coefficient

c) overload capacity is directly proportional to the square of the dispersion coefficient

d) overload capacity is indirectly proportional to the square of the dispersion coefficient

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12. What is the relation between the overload capacity and magnetizing current?

a) overload capacity is directly proportional to the magnetizing current

b) overload capacity is indirectly proportional to the magnetizing current

c) overload capacity is directly proportional to the square of the magnetizing current

d) overload capacity is indirectly proportional to the square of the magnetizing current

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13. What is the relation between ideal short circuit current and the number of poles?

a) short circuit current is directly proportional to the number of poles.

b) short circuit current is directly proportional to the square of the number of poles.

c) short circuit current is indirectly proportional to the number of poles.

d) short circuit current is indirectly proportional to the square of the number of poles.

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14. What is the relation between maximum power and the number of poles?

a) maximum power factor is directly proportional to the number of poles.

b) maximum power factor is directly proportional to the square of the number of poles.

c) maximum power factor is indirectly proportional to the number of poles.

d) maximum power factor is indirectly proportional to the square of the number of poles.

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15. The magnetizing current decreases as the number of poles is decreased?

a) true

b) false

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## Set 3

1. What is the basic property of electrical conducting materials?

a) allows the passage of current through the materials

b) blocks the passage of current through the materials

c) leaks the current through the materials

d) reverses the direction of current in the materials

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2. What is the correct classification of the conducting materials?

a) low resistivity, low conductivity

b) low resistivity, high conductivity

c) high resistivity, high conductivity

d) medium resistivity, medium conductivity

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3. Example of low resistivity material is _____________

a) silver

b) manganese

c) magnesium

d) tungsten

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4. Example of high resistivity material is ________________

a) copper

b) gold

c) aluminum

d) carbon

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5. Is high resistivity material used in making the filaments of incandescent lamp?

a) true

b) false

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6. What materials are used as conductors in the Transmission and Distribution sector?

a) copper

b) silver

c) tungsten

d) carbon

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7. What are the properties of Conducting Materials with respect to temperature coefficient of resistance and tensile strength?

a) low temperature coefficient, low tensile strength

b) low temperature coefficient, high tensile strength

c) high temperature coefficient, low tensile strength

d) high temperature coefficient, high tensile strength

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8. What are the conditions of the conducting materials with respect to melting point and resistance to corrosion?

a) high melting point, low resistance to corrosion

b) low melting point, low resistance to corrosion

c) high melting point, high resistance to corrosion

d) low melting point, high resistance to corrosion

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9. How should the conducting materials be in terms of malleability and ductility?

a) highly malleable, less ductile

b) less malleable, less ductile

c) highly malleable, highly ductile

d) less malleable, highly ductile

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10. Aluminum has high conductivity than Copper.

a) true

b) false

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## Set 4

1. What is the formula of the core length?

a) core length = pole length * pole pitch

b) core length = pole length / pole pitch

c) core length = pole length + pole pitch

d) core length = pole length – pole pitch

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2. What is the range of the ratio of the pole length to pole pitch?

a) 0.60-0.70

b) 0.64-0.72

c) 0.65-0.75

d) 0.70-0.80

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3. What is the maximum value of the peripheral speed that should not exceed?

a) 25 m per sec

b) 20 m per sec

c) 30 m per sec

d) 35 m per sec

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4. What is the range of the pole length to pole pitch ratio for obtaining good power factor in induction motors?

a) 1.5-2

b) 1.3–1.8

c) 1.0-1.25

d) 1.1-1.6

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5. What is the relationship between the diameter and number of poles?

a) diameter is directly proportional to the number of poles

b) diameter is indirectly proportional to the number of poles

c) diameter is directly proportional to the square of the number of poles

d) diameter is indirectly proportional to the square of the number of poles

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6. The core length should be high to obtain high short circuit ratio?

a) true

b) false

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7. What is the factor which is by modern motors which are into a series of standard frames?

a) current rating

b) voltage rating

c) power rating

d) output rating

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8. What is the frame used in the standard frames?

a) set of standard values

b) mechanical structure required to house a rotor of given outside diameter

c) mechanical structure required to house a stator of given outside diameter

d) mechanical structure required to house a stator of given outside length

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9. How can the variation in ratings be obtained?

a) alternative windings

b) alternative core lengths

c) alternative pole pitch

d) alternative pole length

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10. What is the value of the alternative core lengths below which variation in rating can be obtained?

a) 0.7 * length

b) 0.4 * length

c) 0.3 * length

d) 0.7 * length or 0.5 * length

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11. What is the range of the central heights used in the standard frames?

a) 50-1000 mm

b) 90-1000 mm

c) 100-1000 mm

d) 56-1000 mm

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12. The frame size is designated by a number which is its centre height expressed in mm?

a) true

b) false

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## Set 5

1. What is the definition of current transformer?

a) it is used for measuring high voltage

b) it is used for measuring low voltage

c) it is used for measuring high current

d) it is used for measuring low current

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2. How many classifications are present for the current transformers?

a) 1

b) 2

c) 3

d) 4

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3. What is the definition of the ideal current transformer?

a) the primary and secondary windings are in exact ratio and same phase relationship

b) the primary winding and secondary winding ratio is greater than 1 and same phase relationship

c) the primary and secondary winding ratio is lesser than 1 are in exact ratio and different phase relationship

d) the primary and secondary windings ratio is greater than 1 and different phase relationship

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4.How many types of errors are present in the current transformers?

a) 1

b) 2

c) 3

d) 4

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5. What is the formula of the angle between secondary induced voltage and secondary current?

a) phase angle = tan-1 *[(reactance of the secondary winding – reactance of the external burden) / (resistance of the secondary winding + resistance of the external burden)].

b) phase angle = tan-1 *[(reactance of the secondary winding – reactance of the external burden) / (resistance of the secondary winding – resistance of the external burden)].

c) phase angle = tan-1 *[(reactance of the secondary winding * reactance of the external burden) / (resistance of the secondary winding + resistance of the external burden)].

d) phase angle = tan-1 *[(reactance of the secondary winding + reactance of the external burden) / (resistance of the secondary winding + resistance of the external burden)].

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6. What is the formula of the phase angle of the secondary load circuit?

a) phase angle of secondary load circuit = tan-1 * (reactance of the external burden/resistance of the external burden)

b) phase angle of secondary load circuit = tan-1 * (reactance of the external burden + resistance of the external burden)

c) phase angle of secondary load circuit = tan-1 * (reactance of the external burden – resistance of the external burden)

d) phase angle of secondary load circuit = tan-1 * (reactance of the external burden * resistance of the external burden)

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7. What is the formula of the ratio error in the current transformers?

a) ratio error = turns ratio – regulation / regulation

b) ratio error = turns ratio + regulation / regulation

c) ratio error = turns ratio * regulation / regulation

d) ratio error = 1 / turns ratio * regulation

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8. The ratio of active conductor section to total conductor section is called space factor?

a) true

b) false