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# Multiple choice question for engineering

## Set 1

1. What is the formula for the resistance of running winding?
a) resistance of running winding = 0.021 * no of turns in running winding * length of mean turns of running winding * area of running winding conductor
b) resistance of running winding = 0.021 / no of turns in running winding * length of mean turns of running winding * area of running winding conductor
c) resistance of running winding = 0.021 * no of turns in running winding / length of mean turns of running winding * area of running winding conductor
d) resistance of running winding = 0.021 * no of turns in running winding * length of mean turns of running winding / area of running winding conductor

Answer: d [Reason:] First the no of turns in running winding along with length of mean turns of running winding and area of running winding conductor is calculated. On substitution the resistance of running winding is calculated.

2. How many parameters are present in the single phase induction motor?
a) 2
b) 3
c) 4
d) 5

Answer: b [Reason:] There are 3 parameters in the single phase induction motor. They are running winding resistance, rotor resistance and leakage reactance calculations of single phase motor.

3. How many parameters are present under the leakage reactance calculations?
a) 6
b) 5
c) 7
d) 4

Answer: c [Reason:] There are 7 parameters present under the leakage reactance calculations. They are slot leakage reactance, rotor slot leakage reactance, zigzag leakage reactance, overhang leakage reactance, skew leakage reactance, magnetizing reactance, total leakage reactance.

4. How is the winding arrangement and how is the conductors in each slot?
a) circular winding and same conductors in each slot
b) circular winding and different conductor in each slot
c) concentric winding and same conductor in each slot
d) concentric winding and different conductor in each slot

Answer: d [Reason:] The winding of the induction motors are concentric type. The different conductors are being used in each slot.

5. What is the relation of the total slot leakage reactance with number of stator slots?
a) slot leakage reactance is directly proportional to the number of stator slots
b) slot leakage reactance is indirectly proportional to the number of stator slots
c) slot leakage reactance is directly proportional to the square of the number of stator slots
d) slot leakage reactance is indirectly proportional to the square of the number of stator slots

Answer: b [Reason:] The slot leakage reactance is one of the parameters used in the leakage reactance calculations. The slot leakage reactance is indirectly proportional to the number of stator slots.

6. What is the relation between slot leakage reactance and specific slot permeance?
a) slot leakage reactance is directly proportional to the specific slot permeance
b) slot leakage reactance is indirectly proportional to the specific slot permeance
c) slot leakage reactance is directly proportional to the square of the specific slot permeance
d) slot leakage reactance is indirectly proportional to the square of the specific slot permeance

Answer: a [Reason:] Specific slot permeance is one of the parameters present in the leakage reactance calculation. It is directly proportional to the slot leakage reactance.

7. What is the relation of the total slot leakage reactance with number of stator slots?
a) slot leakage reactance is directly proportional to the number of rotor slots
b) slot leakage reactance is indirectly proportional to the number of rotor slots
c) slot leakage reactance is directly proportional to the square of the number of rotor slots
d) slot leakage reactance is indirectly proportional to the square of the number of rotor slots

Answer: b [Reason:] The slot leakage reactance is one of the parameters in the leakage reactance calculation. The slot leakage reactance is indirectly proportional to the number of rotor slots.

8. What is the relation of the zigzag reactance with the specific permeance for zigzag leakage?
a) zigzag reactance is directly proportional to the specific permeance for zigzag leakage
b) zigzag reactance is indirectly proportional to the specific permeance for zigzag leakage
c) zigzag reactance is directly proportional to the square of the specific permeance for zigzag leakage
d) zigzag reactance is indirectly proportional to the square of the specific permeance for zigzag leakage

Answer: a [Reason:] Zigzag reactance is one of the parameters used in the leakage reactance calculation. The zigzag reactance is directly proportional to the specific permeance for zigzag leakage.

9. What is the relation of the stator slot leakage factor with the skew leakage reactance?
a) skew leakage reactance is directly proportional to the stator slot leakage factor
b) skew leakage reactance is indirectly proportional to the stator slot leakage factor
c) skew leakage reactance is directly proportional to the square of stator slot leakage factor
d) skew leakage reactance is indirectly proportional to the square of stator slot leakage factor

Answer: a [Reason:] Skew leakage reactance is one of the parameters used in the leakage reactance calculation. The skew leakage reactance is directly proportional to the stator slot leakage reactance.

10. What is the formula for the rotor bar skew angle?
a) rotor bar skew angle = 3.14 / rotor slot pitches through which bars are skewed * (no of rotor slots / number of poles)
b) rotor bar skew angle = 3.14 * rotor slot pitches through which bars are skewed * (no of rotor slots * number of poles)
c) rotor bar skew angle = 3.14 * rotor slot pitches through which bars are skewed / (no of rotor slots * number of poles)
d) rotor bar skew angle = 3.14 * rotor slot pitches through which bars are skewed / (no of rotor slots / number of poles)

Answer: d [Reason:] The rotor slot pitches through which bars are skewed, number of rotor slots and number of poles are calculated. On substitution the rotor bar skew angle is obtained.

11. What is the value of the stator slot leakage factor?
a) 0.90
b) 0.80
c) 0.95
d) 0.85

Answer: c [Reason:] Stator slot leakage factor is used in the calculation of the skew leakage reactance. The value of the stator slot leakage factor is 0.95 in the single phase induction motor.

12. What is the relation of the overhang leakage reactance with the average coil span in slots?
a) overhang leakage reactance is directly proportional to the square of the average coil span in slots
b) overhang leakage reactance is indirectly proportional to the square of the average coil span in slots
c) overhang leakage reactance is directly proportional to the average coil span in slots
d) overhang leakage reactance is indirectly proportional to the average coil span in slots

Answer: c [Reason:] The overhang leakage reactance is one of the parameters used in the leakage reactance calculation. The overhang leakage reactance is directly proportional to the average coil span in slots.

13. What is the relation between pole pitch and the magnetizing reactance?
a) magnetizing reactance is directly proportional to the square of the pole pitch
b) magnetizing reactance is directly proportional to the pole pitch
c) magnetizing reactance is indirectly proportional to the pole pitch
d) magnetizing reactance is indirectly proportional to the square of the pole pitch

Answer: b [Reason:] The magnetizing reactance is one of the parameters in the leakage reactance calculation. The magnetizing reactance is directly proportional to the pole pitch.

14. The magnetizing reactance is directly proportional to the saturation factor?
a) true
b) false

Answer: b [Reason:] The magnetizing reactance is one of the components used in the leakage reactance calculations. The magnetizing reactance is indirectly proportional to the saturation factor.

15. What is the formula of the saturation factor?
a) saturation factor = total mmf required for magnetic circuit * mmf required for air gap
b) saturation factor = total mmf required for magnetic circuit – mmf required for air gap
c) saturation factor = total mmf required for magnetic circuit / mmf required for air gap
d) saturation factor = total mmf required for magnetic circuit + mmf required for air gap

Answer: c [Reason:] The total mmf required for the magnetic circuit and the mmf required for air gap is calculated. On substitution of the values the saturation factor is calculated.

16. What factor is the core length made equal to in theoretical conditions?
a) pole length
b) pole proportion
c) pole length
d) number of poles

Answer: c [Reason:] The core length is made equal to the pole length in theoretical conditions. But in practical the exact dimensions are governed by manufacturing conditions.

17. What is the output equation of a single phase induction motor developed by P.H Tricky?
a) diameter2 * length = 16.5 / H.P * output coefficient * frequency constant * motor type constants * rpm * 106
b) diameter2 * length = 16.5 * H.P * output coefficient * frequency constant * motor type constants /rpm * 106
c) diameter2 * length = 16.5 * H.P / output coefficient * frequency constant * motor type constants * rpm * 106
d) diameter2 * length = 16.5 * H.P * output coefficient / frequency constant * motor type constants * rpm * 106

Answer: b [Reason:] The output coefficient, horse power, frequency constant, motor type constant along with the speed is calculated. On substitution we get the diameter2 * length value.

## Set 2

1. What are the factors the design of poles of the DC machine depends on?
a) length, breadth, height of the conductors
b) area of cross section of poles
c) area of cross section of poles and height of the poles
d) area of cross section of poles and height of the poles and the design of field windings

Answer: d [Reason:] For designing the poles, first the area of cross section of the poles and the height of the poles should be obtained. Then the field winding design details are also required during the pole design.

2. What is the relationship between flux in the pole body and the useful flux per pole?
a) flux in the pole body is directly proportional to useful flux per pole
b) flux in the pole body is indirectly proportional to the useful flux per pole
c) flux in the pole body is directly proportional to the square of useful flux per pole
d) flux in the pole body is indirectly proportional to the square of useful flux per pole

Answer: a [Reason:] According to the flux in the pole body formula the flux in the pole body is directly proportional to the useful flux per pole. It is also proportional to the leakage coefficient.

3. What is the flux in the pole body, given leakage coefficient = 1.2 and the useful flux per pole is 10 weber?
a) 12 weber
b) 11.2 weber
c) 8.2 weber
d) 20 weber

Answer: a [Reason:] Flux in the pole body = leakage coefficient * useful flux per pole Flux in the pole body = 1.2 * 10 = 12 weber.

4. What is the meaning of useful flux?
a) the flux which is being created in the machine
b) the flux which can be used
c) the flux which can produce the output
d) the flux that is wasted

Answer: c [Reason:] Total flux is the maximum amount of flux which is being generated by the current flowing in the circuit. Useful flux is nothing but the flux which can produce the output in the machine.

5. What is the range of leakage coefficient for output of 100kW?
a) 1.12-1.25
b) 1.11-1.22
c) 1.10-1.20
d) 1.11-1.15

Answer: b [Reason:] 1.12-1.25 is the leakage coefficient when the output is 50kW. 1.10-1.20 is the leakage coefficient when the output is 200kW.

6. What is the range of leakage coefficient for output of 1000kW?
a) 1.12-1.25
b) 1.11-1.22
c) 1.09-1.18
d) 1.08-1.16

Answer: d [Reason:] 1.12-1.25 is the leakage coefficient when the output is 50kW. 1.11-1.22 is the leakage coefficient when the output is 100kW. 1.09-1.18 is the leakage coefficient when the output is 500kW.

7. What is the range of the flux density in the pole shrank for laminated poles?
a) 1.1-1.7 Wb per m2
b) 1.2-1.6 Wb per m2
c) 1.3-1.7 Wb per m2
d) 1.2-1.7 Wb per m2

Answer: d [Reason:] The flux density in the pole shrank of laminated poles should have a minimum value of 1.2. The flux density in the pole shrank of the laminated poles should not exceed 1.7 at the same time.

8. What is the formula for the area of the poles shrank of the laminated poles?
a) area of the pole shrank = flux in the pole body * magnetic field
b) area of the pole shrank = flux in the pole body + magnetic field
c) area of the pole shrank = flux in the pole body – magnetic field
d) area of the pole shrank = flux in the pole body / magnetic field

Answer: a [Reason:] For finding out the area of the pole shrank first the flux in the pole body is found out using the product of the leakage coefficient and the useful flux in the pole. Next, the magnetic field is measured and the product gives the area.

9. What should be the length of pole with respect to the length of the armature and what should be the range of the length of pole?
a) length of pole < length of armature, 10-15 m
b) length of pole > length of armature, 10-15 mm
c) length of pole > length of armature, 10-15 cm
d) length of pole < length of armature, 10-15 mm

Answer: d [Reason:] The length of the pole should be very much less than the length of the armature in order to permit the end play and t avoid magnetic centering. It should be in the range of 10-15 mm.

10. The formula for length of pole is L = Total length of armature – (0.001 to 0.005)?
a) true
b) false

Answer: a [Reason:] First the total length of armature is calculated. Then the value is subtracted by 10-15 mm in order to obtain the length of the pole.

11. What is the formula for the width of pole of DC machines?
a) width of pole body = area of the pole * length of the pole
b) width of pole body = area of the pole + length of the pole
c) width of pole body = area of the pole – length of the pole
d) width of pole body = area of the pole / length of the pole

Answer: d [Reason:] For obtaining the width of the pole, the area of the pole is first obtained. Then the length of the pole is calculated. The ratio of area of the pole to the length of the pole gives the width.

12. The height of the pole depends on the mmf to be provided on the pole at full load ?
a) true
b) false

Answer: a [Reason:] The height of the pole totally depends on the mmf provided to the poles. The mmf provided at full load is only taken into consideration for the height measurement.

13. How is the mmf required at full load obtained for the calculation of height of poles?
a) using closed circuit characteristics
b) using open circuit characteristics
c) using formula
d) using equivalent circuit

Answer: b [Reason:] The mmf at full load is calculated using the magnetization curve. The open circuit characteristics are obtained which help in finding out the mmf at full load.

14. How should the field mmf be with respect to armature mmf to reduce the armature reaction?
a) armature mmf > field mmf
b) armature mmf >= field mmf
c) armature mmf < field mmf
d) armature mmf = field mmf

Answer: c [Reason:] To reduce the armature reaction, the field system should be designed such that the field mmf should be dominant over the armature mmf. If the armature mmf becomes low, the armature reaction reduces.

15. What should be the range of the field mmf to armature mmf ratio at full load?
a) 1.0-1.2
b) 1.1-1.3
c) 1.3-1.5
d) 1.1-1.25

Answer: d [Reason:] The minimum value of the ratio should be atleast 1.1. The maximum value of the ratio should be not greater than 1.25.

## Set 3

1. What happens in the rotating electrical machine?
a) armatures are slotted
b) armatures are slotted and results in the movement of rotor
c) the rotor remains stationary
d) the rotor slots are rotating

Answer: b [Reason:] In the rotating electrical machine, the armatures are slotted and there is movement of rotor. Due to the movement of the rotor there are rapid changes of local gap reluctance.

2. What is pulsation losses?
a) flux pulsations are caused due to the slotted armature
b) flux pulsations are caused due to the rotation of machine
c) flux pulsation occurs due to rotor slots are rotating
d) flux pulsations occur due to the change in reluctance

Answer: d [Reason:] In the rotating electrical machine, the armatures are slotted and there is movement of rotor which leads to changes of local gap reluctance. This change leads to flux pulsations which causes additional losses called pulsating losses.

3. In which machine part/parts does the pulsation loss occurs?
a) teeth
b) pole face
c) conductors
d) teeth and pole faces

Answer: d [Reason:] The pulsation losses occurs in the teeth of the machine. The pulsation losses also occur in the pole faces.

4. How are the pulsation losses aggravated?
a) if the air gap is small compared with slot openings
b) if the air gap is reduced
c) if the air gap is increased
d) if the air gap is made larger than the slot openings

Answer: a [Reason:] The pulsation losses occurs in the pole faces and teeth. The pulsation losses are aggravated if the air gap is small compared with slot openings.

5. The slotting produces harmonic fields which cause high frequency losses near the gap surface?
a) true
b) false

Answer: a [Reason:] The pulsation losses are aggravated if the length of air gap is small than the slot openings. The slotting produces harmonic fields which cause high frequency losses near the gap surface.

6. In which machine is the pulsation losses considerable?
a) synchronous motors
b) induction motors
c) dc shunt motors
d) dc series motors

Answer: b [Reason:] The pulsation losses are aggravated if the length of air gap is small than the slot openings. The pulsation losses although are considerable in the induction motors.

7. What are the factors the permeance depends upon in the zigzag leakage?
a) relative position of stator
b) relative position of rotor
c) relative position of stator and rotor
d) stored energy at any position

Answer: c [Reason:] The permeance for the path of zigzag leakage will depend upon the relative position of stator. The permeance for the path of zigzag leakage will depend upon the relative position of rotor.

8. What is the formula for the stored energy at any position?
a) stored energy at any position = mmf per slot2 * permeance in a particular position
b) stored energy at any position =2 * mmf per slot2 * permeance in a particular position
c) stored energy at any position =1/2 * mmf per slot2 * permeance in a particular position
d) stored energy at any position =1/3 * mmf per slot2 * permeance in a particular position

Answer: c [Reason:] First the mmf per slot along with the permeance in a particular position is calculated. On substitution the stored energy at any position is calculated.

9. What is the formula for the zigzag permeance?
a) zigzag permeance = average width of the rotor tooth / (1/2 * mmf per slot2)
b) zigzag permeance = average width of the rotor tooth * (1/2 * mmf per slot2)
c) zigzag permeance = 1/average width of the rotor tooth *(1/2 * mmf per slot2)
d) zigzag permeance = average width of the rotor tooth *(1/2 / mmf per slot2)

Answer: a [Reason:] The average width of the rotor tooth is first calculated along with the mmf per slot. On substitution the zigzag permeance is found out.

10. What is the formula of the zigzag specific permeance?
a) zigzag specific permeance = average width of the rotor tooth * length / (1/2 * mmf per slot2)
b) zigzag specific permeance = average width of the rotor tooth / length * (1/2 * mmf per slot2)
c) zigzag specific permeance = average width of the rotor tooth * length * (1/2 * mmf per slot2)
d) zigzag specific permeance =1/ average width of the rotor tooth * length * (1/2 * mmf per slot2)

Answer: b [Reason:] The average width of the rotor tooth along with the length and mmf per slot is calculated. On substitution the zigzag specific permeance is obtained.

11. What are the factors the overhang leakage reactance is obtained?
a) length of the overhang
b) diameter of the overhang
c) shape of the overhang
d) length of the overhang along with the shape of the overhang

Answer: d [Reason:] The overhang leakage reactance depends upon the length of the overhang. It also depends upon the shape of the overhang.

12. The overhang leakage reactance depends on the degree of the saturation in the ferromagnetic parts?
a) true
b) false

Answer: a [Reason:] The overhang leakage reactance depends on the length of the overhang and the shape of the overhang. The overhang leakage reactance also depends upon the degree of saturation in the ferromagnetic parts.

13. What is the relation between the overhang specific permeance and the slot pitch?
a) overhang specific permeance is directly proportional to the slot pitch
b) overhang specific permeance is indirectly proportional to the slot pitch
c) overhang specific permeance is directly proportional to the square of the slot pitch
d) overhang specific permeance is indirectly proportional to the square of the slot pitch

Answer: b [Reason:] The overhang specific permeance relation obtained is an empirical relation. In the empirical relation, the overhang specific permeance is indirectly proportional to the slot pitch.

## Set 4

1. When was the computer aided design introduced and who was the founder?
a) 1950, Heroz
b) 1959, Heroz
c) 1959, Veinott
d) 1956, Veinott

Answer: b [Reason:] The commonly accepted papers to machine design were introduced in the year 1959. It was devised by the author Heroz et al.

2. How many commonly accepted papers are present in the machine design?
a) 3
b) 2
c) 4
d) 5

Answer: b [Reason:] There are 2 commonly accepted papers devised by Heroz et al. They are analytic method and synthesis method.

3. What is the concept of analysis method?
a) the choice of dimension alone is made by designer and provided to computer
b) the choice of dimension and materials are made by designer and provided to computer
c) the choice of dimension, materials and types of construction are made by designer and provided to computer
d) the choice of types of construction are made by designer and provided to computer

Answer: c [Reason:] The analysis method is one of the 2 commonly accepted approaches. The choice of dimension, materials, and types of construction are made by designer and provided to computer.

4. How many different approaches are present in the computer aided design ?
a) 2
b) 3
c) 4
d) 5

Answer: c [Reason:] There are 4 types of different approaches present in the computer aided design. They are analysis method, synthesis method, hybrid method, optimisation method.

5. It is fairly easy to program and to use and understand the analysis method?
a) True
b) False

Answer: a [Reason:] Out of the 4 different approaches, analysis method is one commonly used methodology. It is fairly easy to program and to use and understand the analysis method.

6. What happens in the synthesis method?
a) The computer takes its own values
b) Desired performance is given as input to the computer
c) Logical instructions are incorporated in the program
d) Desired performance is given as input along with the logical instruction being incorporated in the program

Answer: d [Reason:] The synthesis method is one of the 4 different approaches in the computer aided design. The desired performance is given as input along with the logical instruction being incorporated in the program.

7. What is the hybrid method of computer aided design?
a) advanced analysis method
b) advanced synthesis method
c) combination of advanced and synthesis method
d) different method

Answer: c [Reason:] They hybrid method is one of the 4 different approaches in the computer aided design. The hybrid method is the combination of advanced and synthesis method.

8. How many transformers are considered in the power system?
a ) 2
b) 3
c) 4
d) 5

Answer: a [Reason:] There are 2 types of transformers used in the power system. They are power transformer and distribution transformer.

9. How many design procedures are present in the design of transformers?
a) 10
b) 9
c) 11
d) 8

Answer: c [Reason:] There are 11 design steps present in the computer aided design of transformers. They are core design, window dimension design, yoke design, overall design, low voltage winding design, high voltage winding design, resistance calculation, leakage reactance calculation, loss calculation, efficiency calculation, no load current calculation.

10. What is the symbol used for the maximum flux density in computer aided designing?
a) Bm
b) Bf
c) Bfd
d) Bmf

Answer: a [Reason:] Computer aided design in one of the design algorithms made use of to design various devices. The symbol used for maximum flux density in computer aided design is Bm.

11.What is the symbol used for the number of turns in the secondary winding?
a) T
b) Tsw
c) Ts
d) Tws

Answer: c [Reason:] Computer aided design in one of the design algorithms made use of to design various devices. The symbol used for number of turns in secondary winding in computer aided design is Ts.

12. What is the symbol used for the mean diameter of the HV/LV winding?
a) Dm
b) Dmp
c) Dms
d) Dmp/Dms

Answer: d [Reason:] Computer aided design in one of the design algorithms made use of to design various devices. The symbol used for mean diameter of the HV/LV winding in computer aided design is Dmp/Dms.

13. What is the symbol used for the resistance referred to HV winding?
a) RR
b) RRw
c) RRp
d) RRhw

Answer: c [Reason:] Computer aided design in one of the design algorithms made use of to design various devices. The symbol used for resistance referred to the HV winding in computer aided design is RRp.

## Set 5

1. What is the concept of power rating of machines with respect to voltage?
a) the required supply voltage for smooth running of the machine
b) the required supply voltage for stopping the machine
c) the required supply voltage for speeding the machine
d) the required supply voltage for slowing up the machine

Answer: a [Reason:] Power rating is nothing but the standard value at which the machine is said to be safe in operation. Rating determines the voltage which allows the smooth running of the machine.

2. What is the concept of power rating of machines with respect to current?
a) Maximum permissible amount of current that can easily flow
b) Minimum permissible amount of current that can easily flow
c) Maximum permissible amount of current that can stop the machine
d) Maximum permissible amount of current that can stop the machine

Answer: a [Reason:] Power rating always deals with two variables, one is current and the other is voltage. When it comes to the current, it is the maximum permitted current that can be allowed into the machine.

3. What happens if there is insufficient rating of the machine?
a) The efficiency of the machine increases
b) The efficiency of the machine improves
c) Damage and shutdown occurs

Answer: c [Reason:] When there is insufficient rating, it can lead to the damage of the windings of the machine. It indirectly, leads to the shutdown of the machine to avoid more hazards.

4. What happens if the power ratings of the machine are decided liberally?
a) Damage occurs to the machine
b) Efficiency of the machine improves
c) Long life of the machine
d) Uneconomical usage of the machine

Answer: d [Reason:] If the power rating becomes very liberal, then it causes a high initial cost. Along with the high initial cost, loss of energy also occurs and leads to uneconomical usage.

5. If the power ratings are crossed, machine breakdown occurs?
a) True
b) False

Answer: a [Reason:] Every machine has a permissible limit for both voltage and current, for its efficient operation. If the limit is crossed, it will lead to the breakdown of the machine.

6. What is one important criteria related to the power ratings of the machine?
a) Heat should be prevented from generation
b) Heat should be dissipated through power ventilation, irrespective of the time
c) Heat should be prevented through power ventilation within a short time period
d) Heat should be converted to some useful form

Answer: c [Reason:] Due to the components present in the machine, I2R losses occur in the machine. Due to this, heat is produced, and proper thermal ventilation should be provided to prevent the machine from breakdown.

7. What is the concept of thermal loading?
a) Output power is indirectly proportional to the temperature rise
b) Output power is indirectly proportional to the square of temperature rise
c) Output power is directly proportional to the temperature rise
d) Output power is directly proportional to the square of temperature rise

Answer: c [Reason:] Thermal loading is nothing, but the increase of the output power with respect to the temperature rise. It can lead to the power rating levels being crossed.

8. What is the ideal condition for thermal dissipation?
a) Heat generated > Heat Dissipated
b) Heat generated < Heat Dissipated
c) Heat generated = Heat Dissipated
d) Heat generated = 0

Answer: c [Reason:] For ideal thermal dissipation, the heat dissipated should be equal to the heat generated. In that case, there will be very less power loss and high efficiency.

9. What is the main objective of power ratings of machines?
a) helps in building a suitable thermal model of machines
b) helps in building a suitable physical model of machines
c) helps in classifying the machines into different types
d) helps to improve the machine efficiency.