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# Multiple choice question for engineering

## Set 1

1. What is the most widely used method for metallurgical temperature measurement?
a) Thermoelectric pyrometer
b) Optical pyrometer
c) Radiation pyrometer
d) Recording pyrometer

### View Answer

Answer: a [Reason:] The most widely preferred method of measurement and control of metallurgical temperature is the thermoelectric pyrometer. It can be used up to a temperature of 3000 F. It consists of a thermocouple, junction block, extension leads, and a recorder.

2. The total emf of the thermoelectric pyrometer is given as ___________
a) Peltier effect
b) Thomson effect
c) Seebeck effect
d) Joule’s method

### View Answer

Answer: c [Reason:] Generation of an emf due to the contact between two dissimilar metals or wires is called Peltier effect. The generation of an emf due to a temperature difference due to opposing ends of the same wire is Thomson effect. The algebraic sum of these four emfs is known as Seebeck effect.

3. The cold junction in a thermoelectric pyrometer is maintained at ________
a) 12 F
b) 32 F
c) 55 F
d) 80 F

### View Answer

Answer: b [Reason:] The Peltier effect of thermoelectric pyrometer involves emf at the hot and cold junctions, whereas Thomson effect deals with emfs along each wire. The cold junction must be kept at a constant temperature of 0oC or 32 F.

4. Chromel-Alumel can be used at a temperature range of __________
a) 300-1400 F
b) 420-600 F
c) 800-1000 F
d) 1200-2200 F

### View Answer

Answer: d [Reason:] Thermoelectric pyrometer makes use of dissimilar materials for the metallic wires to develop an emf. Chromel-Alumel is a commonly used material containing chromel (nickel and chromium) and alumel (nickel, manganese, aluminum, silicon). It is useful at a temperature range of 1200-2200 F.

5. Constantan is an alloy containing _________
a) Nickel and aluminum
b) Silicon, manganese, and aluminum
c) Copper and nickel
d) Aluminum and manganese

### View Answer

Answer: c [Reason:] Thermoelectric pyrometer makes use of dissimilar materials for the metallic wires to develop an emf. One such material is Iron-Constantan. Constantan is an alloy containing 54% copper and 46% nickel. It is useful at a temperature range of 300-1400 F.

6. What is the advantage of copper-constantan over iron-constantan?
a) Low density
b) Low coefficient of expansion
c) Low-temperature measurement
d) Elevated temperature difference

### View Answer

Answer: c [Reason:] Copper-constantan differs from iron-constantan due to the use of copper instead of iron, along with the possible addition of manganese and iron. This is useful for measuring low temperatures up to -420 F and a maximum limit of 600 F.

7. Which material is used when radiation pyrometers don’t produce a satisfactory result?
a) Chromel-Alumel
b) Iron-Constantan
c) Copper-Constantan
d) Rhodium-Platinum

### View Answer

Answer: d [Reason:] 10% Rhodium-Platinum is a noble-metal thermocouple used for measuring very high temperatures. It can be used in a temperature range of 32-3200 F. These are used when radiation or optical pyrometers do not perform satisfactorily.

8. __________are used as protecting tubes in thermocouples above 2000 F.
a) Wrought iron
b) 14% chrome iron
c) Nichrome
d) Porcelain

### View Answer

Answer: d [Reason:] Thermocouples are often covered using protecting tubes. Wrought iron or cast iron can be used as a protecting tube up to 1300 F. 14% chrome iron is used up to 1500 F, whereas 28% chrome iron or nichrome is used up to 2000 F. Above this temperature, porcelain or silicon carbide tubes are used.

9. Which type of pyrometer uses an electric circuit?
a) Controlling pyrometer
b) Optical pyrometer
c) Radiation pyrometer
d) Recording pyrometer

### View Answer

Answer: a [Reason:] A recording pyrometer is used to obtain an entire record of the temperature. On the addition of an electric circuit, it may be used to control the flow of gas. Such a device is known as a controlling pyrometer.

10. A radiation pyrometer is based on ___________
a) Planck’s law
b) Stefan-Boltzmann law
c) Rayleigh-Jeans law
d) Sakuma-Hattori equation

### View Answer

Answer: b [Reason:] The principle of radiation pyrometer is based on a standard radiation body known as a blackbody. These pyrometers are calibrated to indicate blackbody or true temperature. The Stefan-Boltzmann law expresses the rate of radiation energy.

11. What does Stefan-Boltzmann law for radiation pyrometers denote?
a) W = KT4
b) W = KT
c) W = KT-4
d) W = K/T4

### View Answer

Answer: a [Reason:] The principle of radiation pyrometer is based on a standard radiation body known as a blackbody. By Stefan-Boltzmann law, W = KT4 expresses the rate of radiation energy as a proportional to the fourth power of absolute temperature. Here W is the rate of energy emitted and K is a constant of proportionality.

12. What is the maximum usable temperature of radiation pyrometers?
a) 1000 F
b) 5000 F
c) 10000 F
d) No limit

### View Answer

Answer: d [Reason:] The radiation pyrometer does not require direct contact with the hot body. Therefore, the upper limit for temperature is not limited by the ability to withstand high temperatures. The lower limit is 1000 F, whereas by using proper stops there is no upper limit temperature.

13. What can be done to increase the temperature range of optical pyrometers?
a) Better accuracy of telescope
b) Using electrical circuit for control box
c) Inclusion of absorbing screen
d) Using red filter

### View Answer

Answer: c [Reason:] Optical pyrometers have a temperature range of 1400-2400 F. This range can be improved by using an absorbing screen between the lens and the filament. Therefore, by using various absorbing screens the range can be increased to be over 10000 F.

14. What can be done to make the color comparison better for an optical pyrometer?
a) Better accuracy of telescope
b) Using electrical circuit for control box
c) Inclusion of absorbing screen
d) Using red filter

### View Answer

Answer: d [Reason:] An optical pyrometer measures temperature by comparing brightness or the emitted light. To make this comparison easy, a red filter is used. This red filter limits the visible radiation only to the wavelength of red radiation.

## Set 2

1. White bearing metals contain ______ of antimony?
a) 10%
b) 25%
c) 50%
d) 75%

### View Answer

Answer: a [Reason:] All white bearing metals contain about 10% of antimony (Sb) making up its composition. It combines with tin to form an intermetallic compound SbSn. They are hard and have low friction.

2. Tin-based or lead-based alloys are types of ______
a) White metals
b) Copper base alloys
c) Aluminum base alloys
d) Ceramics

### View Answer

Answer: a [Reason:] White bearing metals are either tin-based or lead-based alloys. They contain about 10% of antimony. They are used for medium and high-duty, or low pressure bearing metals.

3. Babbit metals are also known as _______
a) Tin-base alloys
b) Lead-base alloys
c) Copper-base alloys
d) Aluminum-base alloys

### View Answer

Answer: a [Reason:] Tin-base bearing alloys are a type of white bearing metals. They are also known as Babbit metals. They have been named after Isaac Babbitt.

4. How much tin is contained in a Babbit metal?
a) 10%
b) 82%
c) 4%
d) 13%

### View Answer

Answer: b [Reason:] Babbit metals are primarily composed of tin, which is 82% of the total composition. It also contains antimony (10%), copper (4%), and lead (4%). These metals are of a better quality than Lead-base alloys.

5. How much antimony does a lead-base alloy contain?
a) 13%
b) 12%
c) 74%
d) 0.75%

### View Answer

Answer: a [Reason:] Lead-base alloy is a bearing metal primarily composed of lead with a 74% share. It consists of 13% antimony, 12% tin, 0.75% copper, and 0.25% arsenic. These alloys are cheaper than tin-base alloys.

6. ________ types of bearing alloys contain powdered copper and tin.
a) Plain tin bronze
b) Phosphorus bronze
c) Leaded bronze
d) Sintered bronze

### View Answer

Answer: d [Reason:] Sintered bronze is a type of Copper-base bearing alloy. It contains 90% copper powder and 10% tin powder. They are usually self-lubricated.

7. Which type of bearing bronze is the weakest?
a) Plain tin bronze
b) Phosphorus bronze
c) Leaded bronze
d) Sintered bronze

### View Answer

Answer: c [Reason:] Leaded bronze is a Copper-base bearing alloy containing 75% Cu, 5% Sn, 18% Pb, and 2% Ni. They are less stronger than other bearing bronzes. However, they can sustain higher loads than white metals, at higher speeds.

8. Plain tin bronze contains _____ of copper.
a) 85%
b) 88%
c) 75%
d) 90%

### View Answer

Answer: a [Reason:] Plain tin bronze is a type of Copper-base bearing alloy which contains 85% Cu and 15% Sn. Phosphorus bronze contains 88% Cu, whereas leaded bronze contains 75% Cu. 90% of powered Cu is used in sintered bronzes.

9. Which of the following is an application of leaded bronze?
a) Washing machine
b) Extractor fan
c) Vacuum cleaner
d) Aero engine

### View Answer

Answer: d [Reason:] Leaded bronze can sustain high loads at high speeds. This is the reason why they are used to manufacture main bearings of aero engines, and for automobile crankshaft bearings. The outstanding choices indicate applications of sintered bearings.

10. Tin-base alloys are replaced by aluminum-base alloys due to _______
a) High cost
b) Low strength
c) Corrosion
d) Low availability

### View Answer

Answer: a [Reason:] Tin-base bearing alloys are generally more expensive to manufacture. This is the reason why they are being replaced with aluminum-base alloys, as they possess similar strength and characteristics.

11. Bearing materials used for low load applications are ______
a) Ceramic bearing materials
b) Plastic bearing materials
c) White bearing materials
d) Copper-base bearing materials

### View Answer

Answer: b [Reason:] Plastic bearing materials have low coefficients of friction. They are used for low load applications, especially where oil lubrication is undesirable. The common types of plastic bearing materials are Nylon and Teflon.

12. Superalloys have resistance to creep temperatures as high as ______
a) 100
b) 250
c) 500
d) 1000

### View Answer

Answer: d [Reason:] Superalloy is a term used to describe nickel-base and cobalt-base alloys. They have a high strength, resistance to corrosion, and resistance to creep even at 1000.

## Set 3

1. What is the bond energy of iron?
a) 7.8 KJ/mol
b) 401.3 KJ/mol
c) 639.5 KJ/mol
d) 1692.9 KJ/mol

### View Answer

Answer: b [Reason:] The bond energy of a material is defined as the energy required to return the atoms to an infinite separation. Iron forms a metallic bond with a bond energy of 401.3 KJ/mol.

2. Which type of bond is formed in silicon dioxide?
a) Metallic
b) Covalent
c) Ionic
d) Intermolecular

### View Answer

Answer: b [Reason:] The strength of the interatomic bond influences the melting and boiling points of the substances. Silicon dioxide has a covalent bond, whereas sodium chloride and nitrogen are ionic and intermolecular, respectively.

3. What is the bond energy of silicon dioxide?
a) 7.8 KJ/mol
b) 401.3 KJ/mol
c) 639.5 KJ/mol
d) 1692.9 KJ/mol

### View Answer

Answer: d [Reason:] The bond energy of a material is defined as the energy required to return the atoms to an infinite separation. Silicon dioxide forms a covalent bond with a bond energy of 1692.9 KJ/mol. Nitrogen, iron, and sodium chloride have bond energies of 7.8 KJ/mol, 401.3 KJ/mol, and 1692.9 KJ/mol correspondingly.

4. A van der Waals bond is a _________ bond.
a) Primary
b) Secondary
c) Tertiary
d) Quaternary

### View Answer

Answer: b [Reason:] Atomic bonds are classified as either primary bonds or secondary bonds. Primary bonds are further classified as ionic, covalent, and metallic, whereas van der Waals is a secondary bond.

5. Which bond does this representation illustrate?

a) Metallic
b) Covalent
c) Ionic
d) Intermolecular

### View Answer

Answer: a [Reason:] The strength of the interatomic bond influences the melting and boiling points of the substances. In metallic bonding, the valency electrons are not bound to any particular pairs of atoms. These are applied to most pure metals and alloys.

6. Covalent bond is also known as ___________ bond
a) Electrovalent
b) Electrolytic
c) Heteropolar
d) Homopolar

### View Answer

Answer: d [Reason:] Covalent bonds are primary bonds which are formed when electrons are exchanged between atoms. It is also called as a homopolar bond. An ionic bond can also be called a heteropolar of the electrovalent bond.

7. Which among the following is not a type of intermolecular bond?
a) Dispersion
b) Dipole
c) Nitrogen
d) Hydrogen

### View Answer

Answer: c [Reason:] Intermolecular forces are weak forces that account for the mutual interaction between the molecules. These intermolecular bonds are classified as dispersion bonds, hydrogen bonds, and dipole bonds.

8. Which type of bonding does this illustration depict?

a) Dispersion
b) Dipole
c) Ionic
d) Hydrogen

### View Answer

Answer: b [Reason:] The center of positive charge and negative charge are separated. This produces an electrical dipole which provides a mechanism for molecular bonding.

9. How strong is a dipole bond?
a) Stronger than ionic bond
b) Stronger than dispersion bind
c) Weaker than dispersion bond
d) Equal to ionic bond

### View Answer

Answer: b [Reason:] An electrical dipole provides a mechanism for molecular bonding. The presence of a permanent dipole moment increases the attraction forces between molecules. A dipole bond is weaker than an ionic bond but is stronger than a dispersion bond.

## Set 4

1. The beginning of a new phase transformation is known as ________
a) Nucleation
b) Growth
c) Segregation
d) Coring

### View Answer

Answer: a [Reason:] Nucleation is the first step that occurs in the formation of a new phase. In this process, molten metal appears in regions which then become crystals. It involves assembly of atoms by diffusion, changes in structure, and formation of nuclei.

2. In nucleation, particles having radius less than rc are known as _______
a) Nuclei
b) Embryo
c) Element
d) Atom

### View Answer

Answer: b [Reason:] In the homogeneous or self-nucleation process, there is the formation of particles in the melt. When their radius is less than rc(embryo), they tend to redissolve which lowers the energy. Particles having a radius more than rc tend to grow and are called nuclei.

3. How is the critical radius of particles calculated?

### View Answer

Answer: b [Reason:] In nucleation or self-nucleation process, there is the formation of particles in the melt. The critical particle radius is defined as Here, rc is the critical radius and ∆F is the free energy.

4. In the homogeneous nucleation, nucleation rate is maximum __________
a) At freezing point
b) Above boiling point
c) Below melting point
d) At room temperature

### View Answer

Answer: c [Reason:] From the free energy change diagram for homogeneous nucleation, it is seen that the rate of nucleation is affected by a change in temperature. It is maximum at a point below the melting point temperature.

5. Heterogeneous nucleation differs from others due to ________
a) Faster rate of nucleation
b) Supercooling
c) Wetting
d) Growth

### View Answer

Answer: c [Reason:] In heterogeneous nucleation, the liquid metal must be wetted with the foreign particles. Wetting is defined as the spontaneous spreading of one phase over the surface of another. Very little or no supercooling occurs in this type of nucleation.

6. In supercooled metals, the grain growth occurs in ____________ manner.
a) Dendritic
b) Pyramidal
c) Granular
d) Linear

### View Answer

Answer: a [Reason:] Growth is defined as an increase in the size of the nucleus, which occurs after nucleation. Grain growth may occur dendritically if the liquid metal is supercooled.

7. Where does the solidification in a phase diagram start?
a) Liquidus line
b) Solidus line
c) At equilibrium
d) At freezing point

### View Answer

Answer: a [Reason:] In a phase diagram, two phases known as liquidus and solidus exist. Liquidus line is that line above which the alloy is in a liquid state and where solidification starts. At solidus line, the alloy is in solid state and solidification is complete.

8. Which of the following does not apply to non-equilibrium solidification?
a) Porous
b) Dendritic
c) Inhomogeneous
d) Integrated

### View Answer

Answer: d [Reason:] Non-equilibrium solidification occurs under non-equilibrium conditions and involves a fast cooling rate. This results in the formation of porous, dendritic, and cored (segregated) material with inhomogeneous composition.

9. Micro-segregation pattern can be identified using ________ technique.
a) Positron emission radiography
b) Single photon emission computed tomography
c) Magnetic resonance imaging
d) Autoradiography

### View Answer

Answer: d [Reason:] In microsegregation, compositional differences occur on a microscopic level. These samples can be studied by metallographic and autoradiographic techniques.

10. Which of the following does not affects the pattern of segregation?
a) Freezing rate
b) Motion of crystals
c) Rate of solidification
d) Model of development of grain structure

### View Answer

Answer: c [Reason:] Segregation is a common process in cast alloys which alters the microstructure of castings. Freezing rate, the motion of crystals, a model of development of grain structure, and residual liquid under various forces are the factors affecting the degree and pattern of segregation.

11. What is the glass transition temperature of Nylon 6,6?
a) -120oC
b) 50oC
c) 85oC
d) 210oC

### View Answer

Answer: b [Reason:] Glass transition temperature of a material is defined as the temperature at which glass transition occurs. It is denoted by Tg. The value of Tg for Nylon 6,6 is 50oC, and is 265oC when crystallized.

12. Plastic working in the temperature range of 0.3-0.5 Tm is called _________
a) Hot work
b) Cold work
c) Emboss
d) Sheet metal

### View Answer

Answer: b [Reason:] The density of point imperfections and dislocations increases with increasing plastic deformation in the temperature range below 0.3-0.5 Tm. Plastic working below this range is called as cold work. Here, Tm is the melting point in Kelvin.

13. There is _________ change in crystal structure during recrystallization.
a) Major
b) Minor
c) No
d) Constant

### View Answer

Answer: c [Reason:] Recrystallization is defined as the process of nucleation and growth of new strain-free crystals. It starts with heating to temperatures in the range of 0.3-0.5 Tm. In this stage, there is no change in crystal structure.

14. On which factor does the recrystallization temperature depend?
a) Purity
b) Density
c) Melting point
d) Grain size

### View Answer

Answer: a [Reason:] The recrystallization temperature depends on the purity of the material. Very pure materials crystallize around 0.3 Tm, whereas impure materials crystallize around 0.5-0.6 Tm.

15. During grain growth, the number of grains _________ in number.
a) Increase exponentially
b) Increase constantly
c) Decrease
d) Do not change

### View Answer

Answer: c [Reason:] During cold work, the grains become elongated in the direction of working. During crystallization, new grains are formed. During grain growth, the new crystals increase in size but decrease in number.

## Set 5

1. The treatment of steel to get a stronger casing while maintaining a soft core is called _________
a) Surface hardening
b) Tempering
c) Sintering
d) Surface lining

### View Answer

Answer: a [Reason:] In many applications, it is required for the surface to be harder while the core of the material remains soft. The treatment of steels to achieve this is known as surface heat treatment or surface hardening.

2. Which of the following is not a diffusion method of surface heat treatment?
a) Carburizing
b) Cyaniding
c) Induction hardening
d) Carbonitriding

### View Answer

Answer: c [Reason:] The treatment of steels to achieve a hard casing and softer core is known as surface heat treatment or surface hardening. The diffusion methods of surface heat treatment are classified as carburizing, cyaniding, nitriding, and carbonitriding. Thermal methods include flame hardening and induction hardening.

3. Steels containing ________ carbon are used for carburizing.
a) 0.1-0.2%
b) 0.2-0.35%
c) 0.4-0.6%
d) 0.7-0.9%

### View Answer

Answer: a [Reason:] Carburizing the process by which carbon atoms are introduced onto the surface of low-carbon steels to produce a hard casing while the core remains soft. Steels used in carburizing contain carbon content of 0.10-0.20%.

4. Which of the following is not a method of carburizing?
a) Pack carburizing
b) Gas carburizing
c) Cyaniding
d) Nitriding

### View Answer

Answer: d [Reason:] Carburizing the process by which carbon atoms are introduced onto the surface of steels to produce a hard surface while the interior remains soft. When a piece of low-carbon steel is placed in a carbon saturated temperature, the carbon diffuses into the steel and causes carburizing. Pack carburizing, gas carburizing, and liquid carburizing (cyaniding) are three methods of carburizing.

5. The energizer in pack carburizing makes up ________ of the total composition.
a) 10%
b) 25%
c) 40%
d) 80%

### View Answer

Answer: c [Reason:] The carburizing mixture contains a carbon-rich material along with an energizer making up 40% of the total composition. The energizer is composed of soda ash and barium carbonate. It is used to accelerate the carburizing process.

6. What kind of carbon-rich material is used in the carburizing mixture?
a) Charred leather
b) Sodium carbonate
c) Barium carbonate
d) Carbon black

### View Answer

Answer: a [Reason:] The carburizing mixture contains a carbon-rich material like charcoal or charred leather, along with an energizer. The energizer is composed of sodium carbonate (soda ash) and barium carbonate.

7. What is the carburizing temperature?
a) 150-250oC
b) 400-450oC
c) 650-700oC
d) 900-950oC

### View Answer

Answer: d [Reason:] The components to be heat treated and the carburizing mixture are packed in steel boxes and their lids are fixed on the boxes. This is then heat treated at 900-950oC and maintained at this temperature for up to six hours. After carburizing, the components are quenched slowly in the box.

8. Which of the following holds true for pack carburizing?
a) Efficient heating
b) Uniform temperature
c) Easy to handle
d) Not readily adoptable

### View Answer

Answer: d [Reason:] Pack carburizing is a process of carburizing which has several drawbacks. It has inefficient heating, the temperature is not uniform, and is difficult to handle. Furthermore, pack carburizing is not readily available to continuous operation.

9. Prevention of carburizing of components can be done by ___________
a) Adding filler
b) Electroplating
c) Cold working
d) Adding water

### View Answer

Answer: b [Reason:] Sometimes it is desired that a few parts of the surface of the component are prevented from carburizing. In such cases, electroplating the area with copper achieves the desired result. The thickness of electroplating with copper is usually between 0.07 mm to 0.1 mm.

10. Gas carburizing differs from pack carburizing due to the use of ________
a) Silicon-providing gas
b) Mercury-providing gas
c) Carbon-providing gas
d) Argon

### View Answer

Answer: c [Reason:] Gas carburizing overcomes the drawbacks of pack carburizing by replacing the solid carburizing mixture with a carbon-providing gas. In general, natural gas, propane, or generated gas atmospheres are used in these cases.

11. The molten baths used in liquid carburizing are composed of _________
a) 20-50% sodium cyanide, 40% sodium carbonate
b) 40% sodium cyanide, 20-50% sodium carbonate
c) 10% sodium cyanide, 20% sodium carbonate
d) 20% sodium cyanide, 10% sodium carbonate

### View Answer

Answer: a [Reason:] Liquid carburizing is carried out in molten salt baths. These baths contain 20-50% sodium cyanide, 40% sodium carbonate, along with varying quantities of sodium or barium chloride. It is also known as salt carburizing.

12. Liquid carburizing temperature range lies between ________
a) 120-250oC
b) 300-375oC
c) 425-660oC
d) 870-950oC

### View Answer

Answer: d [Reason:] Liquid carburizing is carried out in baths of molten salt containing 20-50% sodium cyanide, 40% sodium carbonate, and with varying quantities of sodium or barium chloride. The cyanide-rich mixture is heated in iron pots to a temperature of 870-950oC. The workpiece is immersed for a little longer than 5-minute periods according to the depth of the case required.

13. Liquid carburizing can be used for producing ________ cases.
a) 0.05-0.1 mm
b) 0.1-0.25 mm
c) 0.3-0.6 mm
d) 0.7-1.0 mm

### View Answer

Answer: b [Reason:] Liquid carburizing is carried out in baths of molten salt baths containing 20-50% sodium cyanide, 40% sodium carbonate, and with varying quantities of sodium or barium chloride. The cyanide-rich mixture is heated in iron pots to a temperature of 870-950oC. This process is suitable for producing shallow cases of 0.1-0.25 mm.

14. Which of the following is not applicable for liquid carburizing?
a) Uniform temperature
b) Dirty work surface
c) Temperature controlled by pyrometers
d) High cost of carburizing

### View Answer

Answer: b [Reason:] Liquid carburizing takes place due to the decomposition of sodium cyanide at the surface of the steel. It has major advantages that the temperature of the salt bath is uniform, the surface of work remains cleans, and that the temperature can be accurately controlled by pyrometers. It also has the disadvantage that the salt pots require batch processing and the cost of carburizing salt is high.