# Multiple choice question for engineering

## Set 1

1. How many factors are present in the relation between rating and dimension of rotating machines?

a) 6

b) 7

c) 8

d) 9

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2. What is the formula of the total magnetic loading?

a) total magnetic loading = total flux around the armature periphery at the air gap

b) total magnetic loading = total number of ampere conductors around the armature for periphery

c) total magnetic loading = number of poles/armature total flux

d) total magnetic loading = total flux/number of poles

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3. What is the formula of the specific electric loading?

a) specific electric loading = total armature ampere conductors * armature periphery at air gap

b) specific electric loading = total flux around the air gap / area of flux path at the air gap

c) specific electric loading = total armature ampere conductors / armature periphery at air gap

d) specific electric loading = total flux around the air gap * area of flux path at the air gap

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4. How many terms can be used to express the output of a machine?

a) 3

b) 4

c) 5

d) 6

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5. How many factors affecting the size of rotating machines?

a) 3

b) 4

c) 5

d) 2

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6. How many factors are used to determine the specific magnetic loading?

a) 2

b) 3

c) 4

d) 5

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7. How many factors are used to determine the specific electric loading?

a) 2

b) 3

c) 4

d) 5

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8. What is the relation between the output and the flux density?

a) flux density is directly proportional to the output

b) flux density is indirectly proportional to the output

c) flux density is directly proportional to the square of the output

d) flux density is indirectly proportional to the square of the output

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9. What is the relation between output and the specific electric loading?

a) specific electric loading is directly proportional to the output

b) specific electric loading is indirectly proportional to the output

c) specific electric loading is directly proportional to the square of the output

d) specific electric loading is indirectly proportional to the square of the output

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10. What is the relation of the specific electric loading and the diameter?

a) specific electric loading is directly proportional to the diameter

b) specific electric loading is indirectly proportional to the diameter

c) specific electric loading is directly proportional to the square of the diameter

d) specific electric loading is indirectly proportional to the square of the diameter

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11. What is the formula of the I^{2}R loss?

a) I^{2}R loss = number of conductors / copper loss in each conductor

b) I^{2}R loss = number of conductors + copper loss in each conductor

c) I^{2}R loss = number of conductors – copper loss in each conductor

d) I^{2}R loss = number of conductors * copper loss in each conductor

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^{2}R loss is obtained.

12. What is the formula of the efficiency of the machine?

a) efficiency = output / output + losses

b) efficiency = output * output + losses

c) efficiency = output – output + losses

d) efficiency = output + output + losses

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13. The fractional horsepower motors have efficiency of order of 98%?

a) true

b) false

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## Set 2

1. How is the flux distributed in the field form?

a) to reduce the high voltage

b) to reduce the high current

c) to reduce the harmonics

d) to keep the total reluctance low

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2. What does the flux distribution curve determine in the ac machine?

a) waveshape of voltage

b) waveshape of current

c) waveshape of power

d) commutation conditions

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3. How many techniques are used to plot the field form in salient pole machines?

a) 2

b) 3

c) 4

d) 5

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4. What is the formula of the flux density in the gap at a distance ‘x’ from the centre of the pole?

a) flux density in the gap at a distance ‘x’ from the centre of the pole = length of air gap at the centre of pole * length of air gap at a distance ‘x’ from the centre of the pole * maximum flux density in air gap

b) flux density in the gap at a distance ‘x’ from the centre of the pole = length of air gap at the centre of pole / length of air gap at a distance ‘x’ from the centre of the pole * maximum flux density in air gap

c) flux density in the gap at a distance ‘x’ from the centre of the pole = length of air gap at the centre of pole * length of air gap at a distance ‘x’ from the centre of the pole / maximum flux density in air gap

d) flux density in the gap at a distance ‘x’ from the centre of the pole = 1/ length of air gap at the centre of pole * length of air gap at a distance ‘x’ from the centre of the pole * maximum flux density in air gap

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5. The plot between carter’s coefficient and the relative flux density is the carter’s fringe curve?

a) true

b) false

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6. What Is the formula of the permeance of the flux tube considering unit depth in the flux plotting technique?

a) permeance of the flux tube = permeability in the air * mean width of flux tube * mean length of flux tube

b) permeance of the flux tube = permeability in the air / mean width of flux tube * mean length of flux tube

c) permeance of the flux tube = permeability in the air * mean width of flux tube / mean length of flux tube

d) permeance of the flux tube =1/ permeability in the air * mean width of flux tube * mean length of flux tube

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7. How many rules are to be followed while the flux plotting by method of curvilinear squares?

a) 2

b) 3

c) 4

d) 5

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8. How many factors does the flux distribution in the rotating machines depend on?

a) 2

b) 3

c) 4

d) 5

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9. How should the flux distribution be in the case of ac machines?

a) sinusoidal

b) rectangular

c) square

d) circular

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10. How should the air gap and the fringing effects be if the field form of a salient pole machine is rectangular?

a) air gap under the pole arc is not constant, fringing effects are considered

b) air gap under the pole arc is constant, fringing effects are considered

c) air gap under the pole arc is constant, fringing effects are not considered

d) air gap under the pole arc is not constant, fringing effects are not considered

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11. What series is used to analyze the field form?

a) z-series

b) fourier series

c) fourier transform

d) z-transform

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12. What happens if the field form is symmetrical about the pole axis?

a) north and south pole of a machine are similar

b) no harmonics

c) no cosine terms

d) north and south pole of a machine are similar, no harmonics, no cosine terms

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13. What Is the formula for the amplitude of the fundamental curve?

a) amplitude of the fundamental curve = 1.27 * flux density in the air gap * cosine (phase angle/2)

b) amplitude of the fundamental curve = 1.27 / flux density in the air gap * cosine (phase angle/2)

c) amplitude of the fundamental curve = 1.27 * flux density in the air gap / cosine (phase angle/2)

d) amplitude of the fundamental curve = 1/1.27 * flux density in the air gap * cosine (phase angle/2)

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## Set 3

1. How many factors are present in the operating characteristics?

a) 2

b) 3

c) 4

d) 5

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2. How many parts does the stator mmf passes through?

a) 3

b) 4

c) 5

d) 6

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3. What is the angle at which the value of the flux density should be for the calculation of mmf?

a) 400

b) 600

c) 800

d) 700

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4.What is the value of the flux density with respect to average flux density?

a) value of flux density = 1.67 times of average flux density

b) value of flux density = 1.70 times of average flux density

c) value of flux density = 1.60 times of average flux density

d) value of flux density = 1.50 times of average flux density

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5. What is the formula for the mmf required for air gap?

a) mmf required for air gap = 8,00,000 * air gap flux density * air gap constant / air gap length

b) mmf required for air gap = 8,00,000 * air gap flux density * air gap constant * air gap length

c) mmf required for air gap = 8,00,000 * air gap flux density / air gap constant * air gap length

d) mmf required for air gap = 8,00,000 / air gap flux density * air gap constant * air gap length

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6. What is the formula for the saturation factor?

a) saturation factor = total mmf required for the magnetic circuit/mmf required for air gap

b) saturation factor = total mmf required for the magnetic circuit + mmf required for air gap

c) saturation factor = total mmf required for the magnetic circuit – mmf required for air gap

d) saturation factor = total mmf required for the magnetic circuit * mmf required for air gap

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7. What is the range of the saturation factor in the single phase induction motor?

a) 1.1-1.3

b) 1.0-1.2

c) 1.1-1.35

d) 1.2-1.6

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8. What is the relation between flux densities with respect to saturation factor?

a) flux density is indirectly proportional to the square of the saturation factor

b) flux density is directly proportional to the square of the saturation factor

c) flux density is indirectly proportional to the saturation factor

d) flux density is directly proportional to the saturation factor

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9. What factors are considered while calculating iron loss in stator teeth and core?

a) flux densities

b) weights

c) flux densities or weights

d) flux densities and weights

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10. What is the relation between total iron loss for induction motors and the sum of stator tooth and core loss?

a) total iron loss for induction motors = 1.3-2.3 times the sum of stator tooth and core loss

b) total iron loss for induction motors = 1.4-2.4 times the sum of stator tooth and core loss

c) total iron loss for induction motors = 1.5-2.5 times the sum of stator tooth and core loss

d) total iron loss for induction motors = 1.3-2 times the sum of stator tooth and core loss

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11. What is the range of the multiplying factor when test data is not available?

a) 1.7-2

b) 1.75-2.2

c) 1.6-2.3

d) 1.5-2

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12. What are the factors which result in the bearing friction and windage loss?

a) ball bearings

b) sleeve bearing

c) ball bearing and sleeve bearing

d) ball bearing or sleeve bearing

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13. What is the friction and windage loss for a 1500 rpm machine?

a) 3-7% of watt output

b) 3-9% of watt output

c) 4-8% of watt output

d) 1-5% of watt output

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14. The high values actually apply for the small motors below 150 W?

a) true

b) false

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15. The loss for the sleeve bearing having stator outer diameter 150 mm and 1000 rpm is 3.7 W?

a) true

b) false

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16. What is the range of the frequency constant?

a) 0.86-1.0

b) 0.82-1.0

c) 0.9-1.0

d) 0.5-1.0

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17. What is the range of the motor type constant?

a) 1.1-1.3

b) 1.0-1.4

c) 1.1-1.42

d) 1.1-1.5

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18. What is the formula of the most economical relation between D and L?

a) length = 0.6 * diameter

b) length = 0.5 / diameter

c) length = 0.6 / diameter

d) length = 0.63 * diameter

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## Set 4

1. What is the formula of the output equation of ac machines?

a) kVA input Q = output coefficient * diameter2 * length * synchronous speed

b) kVA input Q = output coefficient / diameter2 * length * synchronous speed

c) kVA input Q = output coefficient * diameter2 / length * synchronous speed

d) kVA input Q = output coefficient * diameter2 * length / synchronous speed

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2. What is the formula for the output coefficient of the output equation?

a) output coefficient = 11 * winding space factor * specific magnetic loading / specific electric loading * 10^{-3}

b) output coefficient = 11 * winding space factor * specific magnetic loading * specific electric loading * 10^{-3}

c) output coefficient = 11 * winding space factor / specific magnetic loading * specific electric loading * 10^{-3}

d) output coefficient = 11 / winding space factor * specific magnetic loading * specific electric loading * 10^{-3}

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3. What is the formula of the kVA input if the rating of the machine is given in horse power?

a) kVA input = horse power / 0.746 * efficiency * power factor

b) kVA input = horse power * 0.746 * efficiency * power factor

c) kVA input = horse power * 0.746 / efficiency * power factor

d) kVA input = horse power * 0.746 * efficiency / power factor

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4. What is the ratio of the efficiency for 75 watt to 750 watt motor?

a) 4:7

b) 5:7

c) 6:7

d) 3:7

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5. What is the ratio of power factor of the 75 watt to 750 watt motor?

a) 0.55 : 0.60

b) 0.50 : 0.60

c) 0.55 : 0.65

d) 0.50 : 0.65

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6. The smaller values are applicable for lower rating machines?

a) true

b) false

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7. What is the efficiency for the output watt of 180?

a) 0.38

b) 0.48

c) 0.57

d) 0.65

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8. What is the power factor of output watt of 90?

a) 0.46

b) 0.51

c) 0.56

d) 0.62

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9. What factor does the output coefficient depend upon?

a) specific magnetic loading

b) specific electric loading

c) specific electric loading or specific magnetic loading

d) specific electric loading and specific magnetic loading

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10. What is the range of the average flux density used in the output equation?

a) 0.30-0.55 weber per m^{2}

b) 0.30-0.50 weber per m^{2}

c) 0.35-0.45 weber per m^{2}

d) 0.35-0.55 weber per m^{2}

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^{2}. The maximum value of the average flux density is 0.55 weber per m

^{2}.

## Set 5

1. What is the formula for the diameter of the single phase core type transformer?

a) D = diameter of circumscribing circle + Width of window

b) D = diameter of circumscribing circle – Width of window

c) D = diameter of circumscribing circle * Width of window

d) D = diameter of circumscribing circle / Width of window

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2. What is the formula for height of the single phase core type transformer?

a) height = height of the window – height of the yoke

b) height = height of the window + height of the yoke

c) height = height of the window – (2*height of the yoke)

d) height = height of the window + (2*height of the yoke)

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3. What is the formula for width of the single phase core type transformer?

a) width = Width of largest stamping / Diameter of the transformer

b) width = Width of largest stamping + Diameter of the transformer

c) width = Width of largest stamping – Diameter of the transformer

d) width = Width of largest stamping * Diameter of the transformer

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4.What is the formula for the width over 2 limbs?

a) width = Width of largest stamping + Diameter of the transformer

b) width = Diameter + outer diameter of hv windings

c) width = Diameter – outer diameter of hv windings

d) width = outer diameter of hv windings

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5. The formula for single phase core type and three phase core type diameter and height are same?

a) true

b) false

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6. What is the formula for the width over one limb?

a) width over one limb = outer diameter of hv winding

b) width over one limb = 2*Diameter – outer diameter of hv winding

c) width over one limb = 2*Diameter + outer diameter of hv winding

d) width over one limb = Diameter + outer diameter of hv winding

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7. What is the formula for the width of the single phase shell type transformer ?

a) width = 2*Width of the window + width of the largest stamping

b) width = Width of the window + 4*width of the largest stamping

c) width = Width of the window + width of the largest stamping

d) width = 2*Width of the window + 4*width of the largest stamping

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8. What is the height of the single phase shell type transformer?

a) height = height of window + width of the largest stamping

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

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

d) height = height of window – width of the largest stamping

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9. What is the formula to calculate the voltage per turn of the transformer?

a) voltage per turn = space factor * square root of output power

b) voltage per turn = space factor / square root of output power

c) voltage per turn = space factor / square root of output power

d) voltage per turn = space factor * 2*square root of output power

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10. What is the formula for the net cross sectional area of the core of the transformer?

a) cross sectional area = voltage per turn * 4.44 * frequency * magnetic field

b) cross sectional area = voltage per turn / 4.44 * frequency * magnetic field

c) cross sectional area = voltage per turn * 4.44 / frequency * magnetic field

d) cross sectional area = voltage per turn * 4.44 * frequency / magnetic field

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11. What is the formula for the diameter of the circumscribing circle of the transformer?

a) diameter of the circumscribing circle = 2*square root of ratio of cross sectional area of the core to the space factor

b) diameter of the circumscribing circle = 3*square root of ratio of cross sectional area of the core to the space factor

c) diameter of the circumscribing circle = square root of ratio of cross sectional area of the core to the space factor

d) diameter of the circumscribing circle = 4*square root of ratio of cross sectional area of the core to the space factor

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12. What is the formula for the width of the window of the transformer?

a) width of the window = distance between core centers + diameter of the circumscribing circle

b) width of the window = distance between core centers – diameter of the circumscribing circle

c) width of the window = distance between core centers * diameter of the circumscribing circle

d) width of the window = distance between core centers / diameter of the circumscribing circle

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13. What is the formula for window area of the transformer?

a) window area = output power * 2.22 * frequency * magnetic field * window space factor * current density * area of cross section of the core *103

b) window area = output power / 2.22 * frequency * magnetic field * window space factor * current density * area of cross section of the core *103

c) window area = output power / 3.33 * frequency * magnetic field * window space factor * current density * area of cross section of the core *103

d) window area = output power * 3.33 * frequency * magnetic field * window space factor * current density * area of cross section of the core*103

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14. What is the formula for the height of the window?

a) height of window = area of window * width of the window

b) height of window = area of window + width of the window

c) height of window = area of window – width of the window

d) height of window = area of window / width of the window

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15. The range of the ratio of the height of the window to the width of the window is 2-4?

a) true

b) false