Question 1

Which of the following is the major consideration to evolve a good design ?
A)Cost
B)Durability
C)Compliance with performance criteria as laid down in specifications
D)All of the above

Accepted Answer

All of the above factors - cost, durability, and compliance with performance criteria as specified - are major considerations in evolving a good design. Each aspect plays a crucial role in ensuring the design is effective, sustainable, and meets the required standards.

Question 2

impose limitation on design.
A)Saturation
B)Temperature rise
C)Efficiency
D)All above

Accepted Answer

Saturation, temperature rise, and efficiency are all factors that can impose limitations on design. Saturation can limit the maximum output or performance of a device, temperature rise can affect the reliability and safety, and efficiency can constrain how effectively a design converts input to output.

Question 3

The efficiency of a machine should be as ______ as possible to reduce the operating cost.
A)high
B)low
C)either of the above
D)none of the above

Accepted Answer

High efficiency in a machine means it uses less energy to do the same amount of work, which reduces operating costs.

Question 4

If an insulating material is operated beyond the maximum allowable temperature, its life is
A)drastically increased
B)drastically reduced
C)unaffected
D)none of the above

Accepted Answer

Operating an insulating material beyond its maximum allowable temperature can cause it to degrade more quickly, leading to a drastic reduction in its lifespan. This is because excessive heat can break down the material's structure, leading to loss of insulating properties.

Question 5

The design of mechanical parts is particularly important in case of _____ speed machines.
A)low
B)medium
C)high
D)any of the above

Accepted Answer

High-speed machines require precise mechanical design to ensure stability, safety, and efficiency due to the increased forces and stresses involved.

Question 6

In induction motors, the length of air gap in kept as small as mechanically possible is order to have
A)low power factor
B)high power factor
C)high over load capacity
D)any of the above

Accepted Answer

A smaller air gap in induction motors reduces the magnetizing current required, which in turn improves the power factor.

Question 7

In ______ machines, the size of the shaft is decided by the critical speed which depends on the deflection of the shaft.
A)small
B)medium
C)large
D)any of the above.

Accepted Answer

In large machines, the size of the shaft is often determined by the critical speed, which is influenced by the deflection of the shaft. This is because, in large machines, the shafts are longer and more prone to bending or deflection, making the critical speed a significant factor in design considerations to avoid resonance and potential failure.

Question 8

The length cf air gap to be provided in ______ is primarily determined by power factor consideration.
A)d.c. series motor .
B)d.c. shunt motor
C)induction motor
D)synchronous motor

Accepted Answer

The length of the air gap in an induction motor is primarily determined by power factor considerations because it affects the magnetizing current and, consequently, the power factor of the motor.

Question 9

Electrical machines having a power output upto about 750 W may be called_______machines.
A)small size
B)medium size
C)large size
D)any of the above

Accepted Answer

Electrical machines with a power output up to about 750 W are considered small size. This classification is based on their power capacity, with larger machines capable of delivering more power.

Question 10

Electrical machines having power outputs ranging from a few kW upto approximately 250 kW may be classified as
A)small size machines
B)medium size machines
C)large size machines
D)any ofthe above

Accepted Answer

Electrical machines with power outputs in the range of a few kW up to approximately 250 kW are typically classified as medium size machines. This classification helps in understanding their application, design, and operational characteristics.

Question 11

Commercial available medium size machines have a speed range of ______ .
A)200 to 400 r.p.m.
B)600 to 1000 r.p.m.
C)1000 to 1500 r.p.m.
D)2000 to 2500 r.p.m.

Accepted Answer

The answer of Commercial available medium size machines have a...

Question 12

The action of electromagnetic machines can be related to which ofthe following basic principles ?
A)Induction
B)Interaction
C)Alignment
D)All of the above

Accepted Answer

Electromagnetic machines operate based on induction (generation of electromotive force), interaction (forces between magnetic fields and currents), and alignment (orientation of magnetic fields).

Question 13

The change in flux linkages can be caused in which ofthe following ways ?
A)The flux is constant with respect to time and is stationary and the coil moves throughnit
B)The coil is stationary with respect to flux and the flux varies in magnitude with respect to time
C)Both the changes mentioned above occure together, i.e., the coil moves through a time varying field
D)All ofthe above

Accepted Answer

The change in flux linkages can be caused by any of the scenarios mentioned: moving a coil through a stationary but constant flux, having a stationary coil in a time-varying flux, or both moving the coil and having the flux vary over time. All these situations result in a change in the amount of magnetic flux linking the coil, which according to Faraday's law of electromagnetic induction, can induce a voltage in the coil.

Question 14

is universally used for windings of electrical machines because it is easily workable without any possibility of fracture.
A)Silver
B)Steel
C)Aluminium
D)Copper

Accepted Answer

Copper is widely used for windings in electrical machines due to its excellent electrical conductivity and flexibility, which allows it to be easily worked into wires without breaking.

Question 15

Aluminium when adopted as a conductor material in ______ transformers, decreases the overall cost of the transformer
A)small size
B)medium size
C)large size
D)any of the above size

Accepted Answer

The answer of Aluminium when adopted as a conductor material...

Question 16

Which ofthe following materials is used in the manufacture of resistance grids to be used in the starters of large motors ?
A)Copper
B)Aluminium
C)Steel
D)Cast-iron

Accepted Answer

Cast-iron is commonly used for resistance grids in motor starters due to its high resistance and durability.

Question 17

Materials exhibiting zero value of resistivity are known as ______ .
A)conductors
B)semiconductors
C)insulators
D)superconductors

Accepted Answer

Materials that exhibit zero resistivity are known as superconductors. This phenomenon occurs under certain conditions, such as extremely low temperatures, allowing them to conduct electricity without any energy loss.

Question 18

________ has a lowrelative permeability and is used principally in field frames when cost is of primary importance and extra weight is not objectionable.
A)Cast steel
B)Aluminium
C)Soft steel
D)Cast iron

Accepted Answer

Cast iron has a low relative permeability compared to materials like soft steel, making it less efficient for magnetic applications. However, it is used in field frames where cost considerations outweigh the disadvantages of extra weight and lower magnetic efficiency.

Question 19

______is extensively used for those portions of magnetic circuit which carry steady flux and need superior mechanical properties ?
A)Grey cast-iron
B)Cast steel
C)High carbon steel
D)Stainless steel

Accepted Answer

Cast steel is extensively used for parts of the magnetic circuit that carry a steady flux and require superior mechanical properties due to its strength and ability to be cast into complex shapes.

Question 20

Hot rolled sheets have ______ value of permeability
A)zero
B)low
C)high
D)none ofthe above

Accepted Answer

Hot rolled sheets have a low value of permeability due to the alignment of their crystal grains which occurs during the hot rolling process, affecting their magnetic properties.

Quiz 1: Design Considerations and Materials for Electrical Machines

Which of the following is the major consideration to evolve a good design ?

impose limitation on design.

The efficiency of a machine should be as ______ as possible to reduce the operating cost.

If an insulating material is operated beyond the maximum allowable temperature, its life is

The design of mechanical parts is particularly important in case of _____ speed machines.

In induction motors, the length of air gap in kept as small as mechanically possible is order to have

In ______ machines, the size of the shaft is decided by the critical speed which depends on the deflection of the shaft.

The length cf air gap to be provided in ______ is primarily determined by power factor consideration.

Electrical machines having a power output upto about 750 W may be called_______machines.

Electrical machines having power outputs ranging from a few kW upto approximately 250 kW may be classified as

Commercial available medium size machines have a speed range of ______ .

The action of electromagnetic machines can be related to which ofthe following basic principles ?

The change in flux linkages can be caused in which ofthe following ways ?

is universally used for windings of electrical machines because it is easily workable without any possibility of fracture.

Aluminium when adopted as a conductor material in ______ transformers, decreases the overall cost of the transformer

Which ofthe following materials is used in the manufacture of resistance grids to be used in the starters of large motors ?

Materials exhibiting zero value of resistivity are known as ______ .

________ has a lowrelative permeability and is used principally in field frames when cost is of primary importance and extra weight is not objectionable.

______is extensively used for those portions of magnetic circuit which carry steady flux and need superior mechanical properties ?

Hot rolled sheets have ______ value of permeability