# Multiple choice question for engineering

## Set 1

1. The problem of temperature rise and cooling of transformers is essentially the same as that of rotating machinery?

a) true

b) false

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2. How are the losses in the transformer and rotating machines converted to?

a) the losses are converted to electrical energy

b) the losses are converted to electrical and mechanical energy

c) the losses are converted to mechanical energy

d) the losses are converted to thermal energy

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3. In how many ways does heat dissipation occur in transformers?

a) 2

b) 3

c) 4

d) 5

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4. What type of heat dissipation takes place when the heat flows from the outer surface of the transformer part to the oil that cools it?

a) conduction

b) convection

c) conduction and convection

d) radiation

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5. What type of heat dissipation takes place when heat flows from oil to walls of a cooler?

a) conduction

b) convection

c) radiation

d) conduction and convection

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6. What type of heat dissipation takes place when heat flows from the walls of the cooler to the cooling medium?

a) convection

b) radiation

c) convection and radiation

d) conduction and radiation

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7. What is the range of the working temperature of oil determined by the tests?

a) 40-600 C

b) 30-600 C

c) 45-600 C

d) 50-600 C

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8. What is the formula for specific heat dissipation due to convection of oil?

a) specific heat dissipation = 40.3*(temperature difference of the surface relative to oil / height of the dissipating surface)1/4 W per m2- 0C

b) specific heat dissipation = 40.3 / (temperature difference of the surface relative to oil / height of the dissipating surface)1/4 W per m2- 0C

c) specific heat dissipation = 40.3*(temperature difference of the surface relative to oil * height of the dissipating surface)1/4 W per m2- 0C

d) specific heat dissipation = 40.3*(temperature difference of the surface relative to oil + height of the dissipating surface)1/4 W per m2- 0C

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9. What is the value of specific heat dissipation for convection due to air?

a) 8 W per m2- 0C

b) 6 W per m2- 0C

c) 9 W per m2- 0C

d) 10 W per m2- 0C

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10. The convection due to air is 10 times the convection due to oil?

a) true

b) false

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11. How do the walls of the transformer tank dissipate heat?

a) by radiation

b) by convection

c) by conduction

d) by convection and radiation

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12. What is the specific heat dissipated by the plain walled tanks of the transformer by radiation and convection?

a) 6.5, 6 W per m2- 0C

b) 6, 6.5 W per m2- 0C

c) 6.5, 6.5 W per m2- 0C

d) 6, 6 W per m2- 0C

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13. What is the formula for temperature rise of the transformers?

a) temperature rise = total loss * specific heat dissipation * surface temperature

b) temperature rise = total loss / (specific heat dissipation * surface temperature)

c) temperature rise = total loss / specific heat dissipation / surface temperature

d) temperature rise = total loss * specific heat dissipation / surface temperature

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14. Can the plain walled tanks accommodate the transformer for both large and small outputs?

a) the plain walled tanks can accommodate for large outputs but cannot accommodate for small outputs

b) the plain walled tanks can accommodate for large outputs and small outputs

c) the plain walled tanks cannot accommodate for large outputs and small outputs

d) the plain walled tanks can accommodate for small outputs but cannot accommodate for large outputs

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15. How are the ratings of the transformer, losses and temperature rise related?

a) increase, decrease, increase

b) decrease, increase, increase

c) increase, increase, increase

d) decrease, increase, decrease

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## Set 2

1. What is the function of the motor starter with respect to current?

a) to slow the low current flow

b) to prevent the low current flow

c) to allow the large current flow

d) to prevent the large current flow

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2. What is the work of the starter with respect to the mechanical stress?

a) to allow large mechanical stress

b) to restrict large mechanical stress

c) to allow small mechanical stress

d) to restrict small mechanical stress

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3. What is the relation of the current with the starting torque in the starter concept?

a) the starter should restrict current to prevent low starting torque

b) the starter should restrict current to produce high starting torque

c) the starter should send current to prevent low starting torque

d) the starter should send current to produce high starting torque

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4.When does the starter take up liquid rheostat?

a) when the resistance can be varied heavily

b) when the resistance can be varied gradually

c) when the resistance cannot be varied

d) when the resistance should not be varied

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5. The starter take up metallic resistance when the resistance should not be varied in steps ?

a) true

b) false

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6. What happens when the starter takes up metallic resistance?

a) voltage fluctuates from high to low

b) voltage fluctuates between fixed upper and lower limits

c) current fluctuates from high to low

d) current fluctuates between fixed upper and lower limits

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7. What is the product of the ratio of the current and the useful flux per pole?

a) product of ratio of current and useful per pole = (useful flux per pole due to upper limit current * upper limit current) / (useful flux per pole due to lower limit current * lower limit current)

b) product of ratio of current and useful per pole = (useful flux per pole due to upper limit current + upper limit current) / (useful flux per pole due to lower limit current + lower limit current)

c) product of ratio of current and useful per pole = (useful flux per pole due to upper limit current – upper limit current) / (useful flux per pole due to lower limit current – lower limit current)

d) product of ratio of current and useful per pole = (useful flux per pole due to upper limit current * lower limit current) / (useful flux per pole due to lower limit current * upper limit current)

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8. How many machines are considered in the calculation of the resistance steps?

a) 2

b) 3

c) 4

d) 5

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9. What is the concept of notching operation?

a) process of decreasing the voltage

b) process of increasing the efficiency

c) process of cutting out the resistance

d) process of adding on the resistance

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10. What happens in the dc shunt motor when the notching process occurs?

a) flux remains constant

b) speed remains constant

c) voltage remains constant

d) current remains constant

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11. What is the formula of the ratio of the lower limit to upper limit of current with respect to the resistance?

a) lower limit of current / upper limit of current = motor resistance / resistance to limit the starting current

b) lower limit of current / upper limit of current = (motor resistance / resistance to limit the starting current)1/number of resistance

c) lower limit of current / upper limit of current = (motor resistance * resistance to limit the starting current)1/number of resistance

d) lower limit of current / upper limit of current = motor resistance * resistance to limit the starting current

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12. What is the relation of the ratio of rotor current limits and the ratio of lower limit to upper limit current?

a) ratio of rotor current limits = ratio of lower limit to upper limit current

b) ratio of rotor current limits > ratio of lower limit to upper limit current

c) ratio of rotor current limits < ratio of lower limit to upper limit current

d) no relation between ratio of rotor current limits and ratio of lower limit to upper limit current

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13. How many machines are considered for the design of field regulators for dc machines?

a) 2

b) 3

c) 4

d) 5

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14. What is the first step in the design of the field regulators for dc machines?

a) calculation of the resistance of section

b) calculation of the total field circuit resistance

c) calculation of the field circuit resistance

d) resistance to be inserted

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15. What is the second step in the design of the field regulators for dc machines?

a) calculation of the resistance of section

b) calculation of the total field circuit resistance

c) calculation of the field circuit resistance

d) resistance to be inserted

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16. What is the last step involved in the design of field regulators for shunt generators?

a) calculation of the resistance of section

b) calculation of the total field circuit resistance

c) calculation of resistance of section

d) resistance to be inserted

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17. What is the first step in the design of the field regulators for dc motor?

a) number of sections

b) shunt field circuit resistance

c) shunt field resistance

d) resistance of step

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18. What is the plot of the magnetization curve?

a) field current in the y axis vs voltage in x axis

b) field current in the x axis vs voltage in y axis

c) armature current in the y axis vs voltage in x axis

d) armature current in the x axis vs voltage in y axis

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## Set 3

1. What is the use of the turns compensation in current transformer?

a) to increases the ratio error

b) to reduce the ratio error

c) to increase the phase angle error

d) to reduce the phase angle error

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2.What is the formula of the actual ratio?

a) actual ratio = turns ratio + load current * secondary current

b) actual ratio = turns ratio * load current * secondary current

c) actual ratio = turns ratio + load current / secondary current

d) actual ratio = turns ratio / load current * secondary current

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3. What happens if the number of secondary turns is reduced?

a) the primary turns is reduced

b) the output is reduced

c) the efficiency is reduced

d) the transformation ratio is reduced

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4.What is the best number of secondary turns of the current transformer?

a) 1

b) 2

c) 1 or 2 less than the number such that the turns ratio is equal to the nominal current ratio

d) 1 or 2 more than the number such that the turns ratio is equal to the nominal current ratio

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5. The phase angle error is significantly affected by the small change in secondary turns?

a) true

b) false

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6. What is the dimension of the round copper wire made use of in the windings of current transformer?

a) 3 cm^{2}

b) 3 mm^{2}

c) 3 m^{2}

d) 3 cm

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^{2}.

7. What is the range of current density in the windings of the current transformer?

a) 1-3 A per mm^{2}

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

c) 1-2 A per mm^{2}

d) 0.5-2 A per mm^{2}

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^{2}.

8. How many factors are present in the behavior of transformer under short circuit conditions?

a) 2

b) 3

c) 4

d) 5

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## Set 4

1. How many types of electromagnets are present?

a) 2

b) 3

c) 4

d) 5

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2. What is the other name of the Tractive electromagnet and what is the means of movement of the armature?

a) solenoidal, electrical movement

b) solenoidal, mechanical movement

c) traction, electrical movement

d) traction, mechanical movement

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3. What is the supply given to the tractive electromagnets?

a) only dc supply

b) only ac supply

c) ac and dc supply

d) ac or dc supply

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4. Among the following what are the applications of the tractive electromagents?

a) track switches

b) electric bells

c) buzzers

d) track switches, bells,buzzers

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5. How does the portative electromagnet work as?

a) holding magnet

b) connecting magnet

c) repulsion magnets

d) attraction magnets

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6. What type of supply is being provided to the portative electromagnet?

a) only ac supply

b) only dc supply

c) ac and dc supply

d) ac or dc supply

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7. How many most commonly used electromagnets are present?

a) 2

b) 3

c) 4

d) 5

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8. What type of magnet is made use of to produce large force through a relatively small distance?

a) flat-faced armature type

b) horse shoe type

c) flat-faced plunger type

d) flat-faced plunger type and horse shoe type

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9. What material is the flat faced armature type made of?

a) hard steel

b) cast steel

c) cast iron

d) soft steel

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10. How are the air gaps arranged in the flat faced armature type?

a) magnetic in series and mechanical in parallel

b) magnetic in series and parallel

c) mechanical in series and parallel

d) magnetic in parallel and mechanical in series

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11. Which among the following are the application of portative electromagnets?

a) lifting magnets

b) magnetic clutches

c) magnetic chucks

d) lifting magnets, magnetic clutches, magnetic chucks

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12.What is the relation between force and the air gap length in the flat-faced armature type?

a) force is directly proportional to the air gap length

b) force is indirectly proportional to the air gap length

c) force is directly proportional to the square of the air gap length

d) force is indirectly proportional to the square of the air gap length

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13. Horse shoe is usually employed for the small magnets?

a) true

b) false

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14. How many air gaps are present in the flat-faced plunger type?

a) 1

b) 2

c) 3

d) 4

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15. What is the relation of the force and the air gap length in the flat faced plunger type?

a) force is directly proportional to the air gap length

b) force is indirectly proportional to the air gap length

c) force is directly proportional to the square of the air gap length

d) force is indirectly proportional to the square of the air gap length

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## Set 5

1. What is the special feature of single phase induction motor?

a) high starting torque

b) low starting torque

c) average starting torque

d) zero starting torque

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2. How many methods are present in the self starting of the single phase induction motor?

a) 1

b) 2

c) 3

d) 4

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3. What are the names of the windings used in the split phase starting?

a) starting windings

b) auxiliary windings

c) starting or auxiliary windings

d) starting and auxiliary windings

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4.What is the displacement of the running and the starting windings used?

a) running winding displaces the starting winding by 1800

b) running winding displaces the starting winding by 900

c) starting winding displaces the running winding by 900

d) starting winding displaces the running winding by 1800

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5. How is the required phase displacement between the current in the running and starting windings obtained?

a) by connecting a suitable resistor

b) by connecting a suitable capacitor

c) by connecting a suitable inductor

d) by connecting a suitable impedance

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6. When is the starting winding cut out of the circuit in the split phase motor?

a) when the motor speed reaches 65 % of the full load speed

b) when the motor speed reaches 75 % of the full load speed

c) when the motor speed reaches 50 % of the full load speed

d) when the motor speed reaches 85 % of the full load speed

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7. What is the shaded pole starting method?

a) part of the pole is shaded by open circuited copper ring

b) part of the pole is shaded by short circuited copper ring

c) the pole is shaded by open circuited copper ring

d) the pole is shaded by short circuited copper ring

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8. What happens in the shaded pole starting method according to the displacement?

a) displacement between shaded and unshaded portion varies between 200-250

b) displacement between shaded and unshaded portion varies between 200-350

c) displacement between shaded and unshaded portion varies between 200-300

d) displacement between shaded and unshaded portion varies between 300-450

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9. For what type of machines is the shaded pole starting method suitable?

a) for outputs below 60 watt

b) for output below 50 watt

c) for output below 40 watt

d) for output above 50 watt

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10. When is the repulsion motor starting method used?

a) when low starting torque is required

b) when high starting torque is required

c) when high running torque is required

d) when low running torque is required

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11. What is the speciality in the repulsion motor starting method?

a) cage winding is replaced by armature windings

b) cage winding is replaced by field windings

c) cage winding is replaced by commutator windings

d) cage winding is replaced by bearings

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12. What happens in the repulsion motor starting method?

a) the cage windings is dominant

b) the commutator windings are dominant

c) the rotor windings are dominant

d) the stator windings are dominant

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13. What is the range of output watt for the shaded pole induction machine?

a) 0.37-50

b) 90-750

c) 90-3700

d) 7.5-370

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14. What is the range of the starting current of capacitor type induction motor?

a) 5-7

b) 4–6

c) 2-6

d) 2-3

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15. What is the range of the starting torque of shaded pole induction motor?

a) 2-4

b) 2-3.5

c) 0.2-0.3

d) 0.25-0.5