Chapter No. 5
- 1.
- Which of the following is the property of composite material?
- A.
   A high strengthÂ
- B.
B high stiffness Â
- C.
C resistance to corrosionÂ
- D.
D high red hardness
Correct Answer
D. D high red hardnessExplanation
Composite materials are made up of two or more different materials combined together to create a new material with improved properties. High red hardness refers to the ability of a material to maintain its hardness at high temperatures. This property is often desirable in composite materials as it allows them to withstand high temperatures without losing their hardness, making them suitable for applications in high-temperature environments.Rate this question:
- 2.
1. Thermoplastic materials are those materials which__________________
- A.
A are formed into shape under pressure and result in permanently hard product
- B.
B do not become hard with the application of heat and pressure and no chemical change occurs
- C.
C are flexible and can withstand considerable wear under suitable conditions
- D.
D are used as a friction lining for clutches and brakes
Correct Answer
A. A are formed into shape under pressure and result in permanently hard productExplanation
Thermoplastic materials are able to be formed into a specific shape when pressure is applied, and once they cool down, they retain that shape permanently. This is in contrast to thermosetting materials, which undergo a chemical change when heated and cannot be reshaped once they have solidified. Therefore, option A accurately describes the characteristics of thermoplastic materials.Rate this question:
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- 3.
3 Which of the following is not thermosetting plastic?
- A.
A nylons
- B.
B epoxy Â
- C.
C melamine
- D.
 D Bakelite
Correct Answer
A. A nylonsExplanation
Nylons are not thermosetting plastics. Thermosetting plastics are plastics that, once molded and set, cannot be melted or reshaped. Nylons, on the other hand, are thermoplastic materials which can be melted and reshaped multiple times. Therefore, nylons do not fall under the category of thermosetting plastics.Rate this question:
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- 4.
4 The size of nano-particles ranges from ____________
- A.
A 0.1nm-100nmÂ
- B.
  B 10nm-50nm      Â
- C.
     C 1nm-10nm  Â
- D.
D 100nm-1000nm
Correct Answer
A. A 0.1nm-100nmÂExplanation
Nano-particles are extremely small particles with sizes ranging from 0.1nm to 100nm. This range is considered to be the size range for nano-particles. Therefore, option A, 0.1nm-100nm, is the correct answer.Rate this question:
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- 5.
5 Polymers have low density
- A.
A true Â
- B.
B false
Correct Answer
A. A true ÂExplanation
Polymers have low density because they are made up of long chains of repeating molecular units. These chains are loosely packed together, resulting in a material with low density. Additionally, polymers often contain lightweight elements such as carbon and hydrogen, further contributing to their low density.Rate this question:
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- 6.
6 Which of the following is the thermoplastic material?
- A.
A acrylic      Â
- B.
B epoxy  Â
- C.
C melamine
- D.
D Bakelite
Correct Answer
A. A acrylic      ÂExplanation
Acrylic is a type of thermoplastic material that is commonly used in various applications. It is a lightweight and durable material that can be easily molded and shaped when heated. It has good transparency and weather resistance, making it suitable for use in products such as windows, lenses, and outdoor signs. Acrylic is also known for its high impact strength and resistance to chemicals, making it a popular choice for items such as aquariums and protective barriers. Therefore, option A, acrylic, is the correct answer as it is a thermoplastic material.Rate this question:
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- 7.
7 Which of the following is the chemically inert to organic solvents?
- A.
A thermoplastic plastic
- B.
B thermosetting plastic
Correct Answer
B. B thermosetting plasticExplanation
Thermosetting plastics are chemically inert to organic solvents. This means that they do not react or dissolve when exposed to organic solvents. Unlike thermoplastic plastics, which can melt and be reshaped when heated, thermosetting plastics undergo a chemical reaction when heated and become permanently set. This chemical reaction creates a cross-linked network structure that makes them resistant to solvents. Therefore, thermosetting plastics are the correct answer as they do not react with or dissolve in organic solvents.Rate this question:
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- 8.
8 Which of the following is used in automobile tyres?
- A.
A chloroprene   Â
- B.
     B SBR                   Â
- C.
C NBRÂ Â Â Â Â
- D.
           D silicones
Correct Answer
B. Â Â Â Â Â B SBRÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ÂExplanation
SBR, or Styrene-Butadiene Rubber, is commonly used in automobile tires due to its excellent abrasion resistance, durability, and low rolling resistance. It provides good traction on both wet and dry surfaces, making it suitable for various road conditions. SBR also offers good heat resistance and flexibility, allowing the tires to withstand high temperatures and maintain their shape. Additionally, SBR is cost-effective and easily produced, making it a popular choice for tire manufacturers.Rate this question:
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- 9.
1. Which of the following are used in sanitary wares?
- A.
A silicones
- B.
B ceramics    Â
- C.
   C nylons Â
- D.
D polyester
Correct Answer
B. B ceramics    ÂExplanation
Ceramics are commonly used in sanitary wares. They are durable, non-porous, and resistant to stains, making them ideal for use in bathroom fixtures such as sinks, toilets, and bathtubs. Ceramics also have a smooth surface, which makes them easy to clean and maintain. Additionally, ceramics can withstand high temperatures and are not easily damaged by chemicals or moisture, further enhancing their suitability for use in sanitary wares.Rate this question:
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- 10.
10. ________ is formed by mixing hydrochloric acid, limestone and natural gas.
- A.
A Acrylics                   Â
- B.
B ABSÂ Â Â Â Â Â Â Â Â Â
- C.
C PVCÂ Â
- D.
D Bakelite
Correct Answer
C. C PVCÂ ÂExplanation
PVC (Polyvinyl Chloride) is formed by mixing hydrochloric acid, limestone, and natural gas.Rate this question:
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- 11.
11. ________ can be reshaped after heating.
- A.
A thermosetting plastic Â
- B.
B thermoplastic plastic
Correct Answer
A. A thermosetting plastic ÂExplanation
Thermosetting plastic can be reshaped after heating because it undergoes a chemical change when heated, which causes it to harden and become permanently rigid. This process is irreversible, so once a thermosetting plastic has been heated and shaped, it cannot be melted or reshaped again. In contrast, thermoplastic plastics can be melted and reshaped multiple times because they only undergo a physical change when heated, allowing them to be molded and remolded as needed.Rate this question:
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- 12.
1. Which of the following is used in fluorescent light reflectors?
- A.
A PVCÂ
- B.
B polystyreneÂ
- C.
C elastomers
- D.
   D nylons
Correct Answer
A. A PVCÂExplanation
PVC (Polyvinyl Chloride) is used in fluorescent light reflectors because it has good reflective properties and is resistant to heat and chemicals. It is also lightweight and easy to shape, making it suitable for use in reflectors. Polystyrene, elastomers, and nylons do not have the same reflective properties or resistance to heat and chemicals as PVC, which is why they are not used in fluorescent light reflectors.Rate this question:
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- 13.
13. Thermosetting plastic are those materials which__________________
- A.
A are formed into shape under pressure and result in permanently hard product
- B.
B do not become hard with the application of heat and pressure and no chemical change occurs
- C.
C are flexible and can withstand considerable wear under suitable conditions
- D.
D are used as a friction lining for clutches and brakes
Correct Answer
A. A are formed into shape under pressure and result in permanently hard productExplanation
Thermosetting plastics are materials that undergo a chemical change when heated and molded under pressure. This chemical change causes the plastic to cross-link and form a rigid and permanently hard product. Unlike thermoplastics, which can be melted and reshaped multiple times, thermosetting plastics cannot be remolded once they have undergone this chemical change. Therefore, option A correctly describes the characteristic of thermosetting plastics.Rate this question:
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- 14.
14. Polyvinylchloride (PVC) is a _____ material
- A.
A thermoplasticÂ
- B.
B thermosetting
Correct Answer
A. A thermoplasticÂExplanation
PVC is classified as a thermoplastic material because it can be melted and re-melted multiple times without undergoing any significant chemical change. Thermoplastics have a linear or branched structure, and they soften when heated and harden when cooled. This property allows PVC to be easily molded into various shapes and forms, making it a versatile material for many applications. On the other hand, thermosetting materials undergo a chemical change when heated and cannot be melted or reshaped once they have been set.Rate this question:
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- 15.
15. _____ is a mixture of both paint and varnish.
- A.
A cellulose     Â
- B.
 B enamel Â
- C.
C latexÂ
- D.
D melamine
Correct Answer
A. A cellulose      -
- 16.
16. Rubber is a linear polymer.
- A.
A trueÂ
- B.
B false
Correct Answer
A. A trueÂExplanation
Rubber is a linear polymer because it consists of long chains of repeating monomer units that are connected in a straight line. This linear structure gives rubber its unique properties such as elasticity and flexibility.Rate this question:
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- 17.
17.Which kinds of materials are used in civil structures?
- A.
A Piezoelectric materialÂ
- B.
B Magneto restrictive material
- C.
C Polymer gel      Â
- D.
D Shape memory materials
Correct Answer
D. D Shape memory materialsExplanation
Shape memory materials are used in civil structures. These materials have the ability to "remember" their original shape and return to it after being deformed. This property makes them ideal for applications in civil engineering, such as in bridges and buildings, where they can be used to absorb and recover from structural deformations caused by external forces or environmental conditions. Shape memory materials can enhance the safety and durability of civil structures by providing them with the ability to self-repair and adapt to changing conditions.Rate this question:
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- 18.
18. Which of the following is solid under the trade name ‘Perspex’?
- A.
A Polyamides            Â
- B.
B Poly methyl methacrylate
- C.
C PVCÂ Â Â
- D.
D Melamine
Correct Answer
B. B Poly methyl methacrylateExplanation
Perspex is a trade name for Poly methyl methacrylate, commonly known as acrylic. Acrylic is a transparent thermoplastic that is often used as a lightweight and shatter-resistant alternative to glass. It is commonly used in applications such as windows, signs, displays, and lighting fixtures.Rate this question:
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- 19.
19. Which of the following is laminated composite?
- A.
A alcad  Â
- B.
B cement concreteÂ
- C.
C reinforced concrete
- D.
 D hybrid composites
Correct Answer
A. A alcad  ÂExplanation
Alcad is a type of laminated composite material. Laminated composites are made by layering multiple materials together, typically alternating between layers of reinforcement and matrix materials. Alcad is a specific type of laminated composite that is made by bonding layers of aluminum and copper together. This material is commonly used in electrical applications due to its high electrical conductivity and low electrical resistance. Therefore, option A, alcad, is the correct answer as it is a laminated composite material.Rate this question:
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- 20.
20.Melting point of nano material decreases with decrease in size of particle.
- A.
A true  Â
- B.
B false
Correct Answer
A. A true  ÂExplanation
As the size of a particle decreases, the ratio of surface area to volume increases. This means that there is a larger surface area available for interactions with the surroundings. In the case of nano materials, this increased surface area leads to more atoms or molecules being present at the surface, which results in weaker intermolecular forces. Consequently, the particles require less energy to break these weak intermolecular forces and transition from a solid to a liquid state, resulting in a lower melting point. Therefore, the statement that the melting point of nano materials decreases with a decrease in size of the particle is true.Rate this question:
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- 21.
21.Which one of the following processes is used for making high power magnets
- A.
A powder metallurgyÂ
- B.
   B nano technology  Â
- C.
C polymerizationÂ
- D.
D none of these
Correct Answer
B.    B nano technology  ÂExplanation
Nano technology is the process used for making high power magnets. This technology involves manipulating and controlling materials at the nanoscale level, which allows for the creation of magnets with enhanced properties such as higher magnetic strength and improved performance. Powder metallurgy and polymerization are not specifically used for making high power magnets, and the option "none of these" is incorrect as nano technology is indeed the correct answer.Rate this question:
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- 22.
22. Nano materials are used for water purification in desalinization by reverse.
- A.
A correct Â
- B.
B incorrect
Correct Answer
A. A correct ÂExplanation
Nano materials are used for water purification in desalination by reverse osmosis. Reverse osmosis is a process that removes salt and other impurities from seawater to make it suitable for drinking. Nano materials, such as nanotubes and nanofibers, have unique properties that make them effective in water purification processes. They have a large surface area, which allows for more efficient adsorption and filtration of contaminants. Additionally, their small size allows them to easily pass through membranes, increasing the overall efficiency of the desalination process.Rate this question:
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- 23.
23 Which of the following is not a reinforced composits?
- A.
A wood       Â
- B.
B FRPÂ Â Â
- C.
C hybrid composite
- D.
D alcad
Correct Answer
D. D alcadExplanation
The correct answer is D alcad because alcad is not a type of reinforced composite material. It is not a commonly known or used material in the field of composites.Rate this question:
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- 24.
24. Which of the followings are used in wind screen of motors?
- A.
A glass-woolÂ
- B.
B silicones Â
- C.
C glasses
- D.
D PVC
Correct Answer
C. C glassesExplanation
Glasses are used in the windscreen of motors.Rate this question:
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- 25.
25 Which of the followings are used in contact lenses?
- A.
A Polymethyl methacrylate (PMMA)Â Â
- B.
   B epoxy resins
- C.
C ABSÂ Â Â Â Â Â Â
- D.
D nylons
Correct Answer
A. A Polymethyl methacrylate (PMMA)Â ÂExplanation
Polymethyl methacrylate (PMMA) is used in contact lenses.Rate this question:
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- 26.
26 _____discolors on ageing by sunlight.
- A.
A Phenol formaldehyde
- B.
 B nylons
- C.
   C acrylicsÂ
- D.
D ABS
Correct Answer
A. A pHenol formaldehydeExplanation
Phenol formaldehyde is a type of plastic that is known to discolor on aging when exposed to sunlight. This is because the UV radiation in sunlight can cause the chemical structure of the plastic to break down, leading to a change in color. This is a common phenomenon observed in many types of plastics, and it is important to consider this when using or selecting materials for outdoor applications.Rate this question:
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- 27.
27 Which of the following is a copolymer of acrylonitrile, butadiene and styrene?
- A.
A Polyester
- B.
 B ABS
- C.
C acrylics Â
- D.
D PVC
Correct Answer
B. Â B ABSExplanation
ABS (Acrylonitrile Butadiene Styrene) is a copolymer made up of three monomers: acrylonitrile, butadiene, and styrene. It is a thermoplastic material that is known for its high impact resistance and strength. ABS is commonly used in various applications such as automotive parts, toys, and household appliances.Rate this question:
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- 28.
28 ______have three dimensional molecular structure.
- A.
A thermoplastic plastic
- B.
B thermosetting plastic
Correct Answer
B. B thermosetting plasticExplanation
Thermosetting plastics have a three-dimensional molecular structure. Unlike thermoplastic plastics, which can be melted and reshaped multiple times, thermosetting plastics undergo a chemical reaction during the curing process that permanently sets their shape. This chemical reaction creates strong cross-linking bonds between the polymer chains, resulting in a rigid and infusible material. Therefore, the correct answer is B thermosetting plastic.Rate this question:
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- 29.
29 Which of the following should not be heated above their decomposition temperature?
- A.
A thermoplastic plastic
- B.
  B thermosetting plastic
Correct Answer
A. A thermoplastic plasticExplanation
Thermoplastic plastics should not be heated above their decomposition temperature because they will break down and lose their structural integrity. Unlike thermosetting plastics, which can withstand high temperatures without decomposing, thermoplastic plastics can melt and become deformed when exposed to excessive heat. Therefore, it is important to carefully control the temperature when working with thermoplastic plastics to avoid damaging or destroying the material.Rate this question:
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- 30.
30 Which of the following is not product of thermosetting plastics?
- A.
A vulcanized rubber
- B.
       B Bakelite
- C.
 C melamine  Â
- D.
D PVC
Correct Answer
D. D PVCExplanation
PVC (Polyvinyl chloride) is not a product of thermosetting plastics. Thermosetting plastics are materials that undergo a chemical reaction when heated and cannot be reshaped or remolded once they have solidified. PVC, on the other hand, is a type of thermoplastic that can be melted and reshaped multiple times without undergoing any chemical change. Therefore, PVC does not belong to the category of thermosetting plastics.Rate this question:
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- 31.
31Which of the following is used for heavy duty conveyor belts?
- A.
A SBRÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
- B.
B NBRÂ Â Â Â Â Â Â Â Â Â Â Â Â Â
- C.
C neoprene    Â
- D.
        D silicones
Correct Answer
C. C neoprene    ÂExplanation
Neoprene is a synthetic rubber that is commonly used for heavy duty conveyor belts. It is known for its durability, resistance to abrasion, and ability to withstand high temperatures. Neoprene also has good resistance to oils, chemicals, and UV radiation, making it suitable for use in industrial applications. Therefore, neoprene is the preferred choice for heavy duty conveyor belts.Rate this question:
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- 32.
32 density of glass wool is ________
- A.
A 50 kg/m3Â Â
- B.
B 24 kg/m3
- C.
C 126 kg/m3Â Â Â Â
- D.
D 42 kg/m3
Correct Answer
B. B 24 kg/m3Explanation
The density of glass wool is a measure of how much mass is contained within a given volume. A lower density indicates that there is less mass packed into the same volume, while a higher density indicates more mass packed into the same volume. Therefore, a density of 24 kg/m3 means that there is less mass in each cubic meter of glass wool compared to the other options provided.Rate this question:
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- 33.
33 _ can be used in both heat and cold insulation.
- A.
A PVCÂ Â Â Â Â Â Â Â Â
- B.
B glasswoolÂ
- C.
C NBRÂ Â Â
- D.
 D ABS
Correct Answer
B. B glasswoolÂExplanation
Glasswool is a type of insulation material that can be used in both heat and cold insulation. It is made from recycled glass and has excellent thermal insulation properties. It is able to trap air pockets within its structure, which helps to reduce heat transfer through conduction. This makes it effective in both hot and cold environments, making it a versatile choice for insulation applications.Rate this question:
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- 34.
34 Resilience of NBR is _____that of natural rubber.
- A.
A one third Â
- B.
B one fourth Â
- C.
C twice     Â
- D.
D thrice
Correct Answer
A. A one third ÂExplanation
The correct answer is A) one third. This means that the resilience of NBR is one third of the resilience of natural rubber.Rate this question:
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- 35.
35 Which of the following is not an application of nano material?
- A.
A cutting tools   Â
- B.
B medical implantÂ
- C.
 C electric parts  Â
- D.
D high power magnets
Correct Answer
C.  C electric parts  ÂExplanation
Nano materials have a wide range of applications, including in cutting tools, medical implants, and high power magnets. However, they are not commonly used in electric parts.Rate this question:
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- 36.
36 Which of the following is not used for manufacturing of ceramics?
- A.
A injection moulding Â
- B.
   B sintering  Â
- C.
 C hot processing  Â
- D.
D rolling
Correct Answer
D. D rollingExplanation
Rolling is not used for manufacturing ceramics because it is a process primarily used for shaping metals. Ceramics are typically formed through methods such as injection molding, sintering, and hot processing, which involve the use of heat and pressure to shape and solidify ceramic materials. Rolling, on the other hand, involves passing a metal material between two rollers to reduce its thickness or change its shape. Therefore, rolling is not a suitable method for manufacturing ceramics.Rate this question:
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- 37.
1. __ is used for low voltage insulation.
- A.
A NBRÂ Â Â Â Â Â Â
- B.
   B chloroprene     Â
- C.
      C epoxy resins
- D.
     D polyester
Correct Answer
B.    B chloroprene     ÂExplanation
Chloroprene is used for low voltage insulation because it has excellent electrical insulation properties and can withstand low voltage conditions without any breakdown or leakage. It has good dielectric strength and can effectively prevent the flow of electric current. Chloroprene is also resistant to oils, chemicals, and heat, making it suitable for various applications where low voltage insulation is required.Rate this question:
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- 38.
38 Which of the following is self extinguished when ignited?
- A.
A rubbers  Â
- B.
 B Bakelite  Â
- C.
C PVCÂ Â
- D.
D silicones
Correct Answer
C. C PVCÂ ÂExplanation
PVC (Polyvinyl chloride) is a type of plastic that is self-extinguishing when ignited. This means that if PVC catches fire, it will stop burning on its own once the source of ignition is removed. This property is due to the presence of chlorine in PVC, which helps to suppress the combustion process. As a result, PVC is commonly used in applications where fire safety is important, such as electrical wiring and building materials.Rate this question:
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- 39.
39 Which of the following is highly cross linked polymers?
- A.
A melamineÂ
- B.
B epoxy resins
- C.
C BakeliteÂ
- D.
D silicones
Correct Answer
A. A melamineÂExplanation
Melamine is a highly cross-linked polymer. It is made up of repeating units of formaldehyde and melamine, which are cross-linked together through chemical bonds. This cross-linking gives melamine its strong and durable properties, making it suitable for use in a variety of applications such as kitchenware, countertops, and laminates.Rate this question:
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- 40.
40 Which of the following is not an application of polyethyelene terephthalate?
- A.
A mattress
- B.
B adhesivesÂ
- C.
C electrical connectionsÂ
- D.
D coatings
Correct Answer
C. C electrical connectionsÂExplanation
Polyethylene terephthalate (PET) is commonly used in various applications due to its properties such as strength, durability, and resistance to chemicals. It is commonly used in the production of bottles, packaging materials, and textiles. However, it is not typically used in electrical connections. This is because PET is not a good conductor of electricity and may not provide the necessary conductivity and safety required for electrical connections. Therefore, it is not commonly used in this application.Rate this question:
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- 41.
41 ___ is manufactured by addition polymerization of methyl methacrylate?
- A.
A polyester         Â
- B.
B PVCÂ Â Â
- C.
C PMMAÂ Â Â Â Â
- D.
D epoxy resins
Correct Answer
C. C PMMAÂ Â Â Â ÂExplanation
PMMA, or polymethyl methacrylate, is a type of plastic that is manufactured through addition polymerization of methyl methacrylate. It is commonly known as acrylic or acrylic glass and is used in various applications such as windows, lenses, and signage. PMMA is known for its transparency, durability, and weather resistance, making it a popular choice in many industries.Rate this question:
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- 42.
42. which of the following is not an application of NBR ?
- A.
A Flexible couplings
- B.
B printing blanketsÂ
- C.
C rubber roller
- D.
 D paints
Correct Answer
D. Â D paints -
- 43.
43. ____ is used to form riffle barrel which is stronger and lighter.
- A.
A silicones Â
- B.
B SBRÂ
- C.
C glasses
- D.
D glasswool
Correct Answer
C. C glassesExplanation
Glasses are used to form riffle barrel which is stronger and lighter. Glasses have a high strength-to-weight ratio, making them an ideal material for creating a strong and lightweight structure like a riffle barrel.Rate this question:
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- 44.
44. _____ is a mixture of silica and basic oxides.
- A.
A glasswoolÂ
- B.
B glasses
- C.
C silicones  Â
- D.
D rubber
Correct Answer
B. B glassesExplanation
Glasses are a mixture of silica and basic oxides. Silica is the main component of glass, while basic oxides such as sodium oxide or calcium oxide are added to give glass its desired properties. Therefore, glasses can be considered as a mixture of silica and basic oxides.Rate this question:
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- 45.
45. _____ is used for thermal and sound insulation in aeroplanes.
- A.
A glasswool      Â
- B.
B glasses     Â
- C.
C silicones    Â
- D.
D rubber
Correct Answer
A. A glasswool      ÂExplanation
Glasswool is a type of insulation material that is commonly used in aeroplanes for both thermal and sound insulation. It is made from fine glass fibers that are woven together to form a dense mat. The structure of glasswool traps air pockets, which helps to prevent the transfer of heat and sound. It is lightweight, flexible, and has excellent thermal and acoustic properties, making it an ideal choice for insulation in aeroplanes.Rate this question:
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- 46.
46. ____ is used in column and beams for construction.
- A.
A hybrid composites
- B.
 B wood
- C.
C reinforced concrete  Â
- D.
D FRP
Correct Answer
C. C reinforced concrete  ÂExplanation
Reinforced concrete is used in columns and beams for construction because it combines the strength and durability of concrete with the added reinforcement of steel bars or mesh. This combination allows the concrete to withstand higher loads and resist cracking and bending, making it suitable for supporting heavy structures. Reinforced concrete is commonly used in construction due to its versatility, cost-effectiveness, and ability to be molded into various shapes and sizes.Rate this question:
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- 47.
47. The melting point increases with decrease in size of nano particles
- A.
A correct  Â
- B.
B incorrect
Correct Answer
B. B incorrectExplanation
The correct answer is B incorrect. The melting point actually decreases with a decrease in the size of nano particles. This is due to the fact that as the size of particles decreases, the surface area to volume ratio increases. This leads to an increase in surface energy, which lowers the melting point. Additionally, the reduced size of particles also affects the crystal structure and atomic arrangement, further contributing to the decrease in melting point.Rate this question:
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- 48.
48. which are methods for synthesis of nano particles ? `
- A.
A bottom- up approach
- B.
B top-down approach Â
- C.
c both A & B
- D.
D none of the above
Correct Answer
C. c both A & BExplanation
Both the bottom-up and top-down approaches are methods for the synthesis of nanoparticles. The bottom-up approach involves building nanoparticles from smaller components or atoms, gradually assembling them into larger structures. On the other hand, the top-down approach involves breaking down larger materials into nanoparticles through techniques such as grinding, milling, or lithography. Therefore, both A (bottom-up approach) and B (top-down approach) are valid methods for synthesizing nanoparticles.Rate this question:
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- 49.
49. ____ absorbs 100% light and hence, does not shine.
- A.
A gold nano particles
- B.
B zinc sulphide
- C.
 C titanium carbide
- D.
D cadmium sulphide
Correct Answer
A. A gold nano particlesExplanation
Gold nanoparticles absorb 100% of light and do not shine because of a phenomenon called surface plasmon resonance. When light interacts with gold nanoparticles, the electrons in the metal oscillate collectively, absorbing the light energy and converting it into heat. This absorption of light prevents the gold nanoparticles from reflecting or scattering light, resulting in their lack of shine. Zinc sulphide, titanium carbide, and cadmium sulphide do not have the same properties and therefore do not absorb 100% of light.Rate this question:
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- 50.
50. which of the following are applications of neoprene ?
- A.
A hose covers
- B.
B footwear
- C.
C brake diaphragms
- D.
D all of the above
Correct Answer
D. D all of the aboveExplanation
Neoprene is a type of synthetic rubber that has various applications. It is known for its resistance to oil, heat, and weathering, making it suitable for different purposes. A hose cover made of neoprene can provide protection and insulation for hoses, while neoprene footwear can offer durability and waterproofing. Neoprene is also commonly used in brake diaphragms due to its ability to withstand high temperatures and resist chemical degradation. Therefore, all of the given options (A, B, and C) are correct applications of neoprene.Rate this question:
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