Multiple choice question for engineering
Set 1
1. Which of the following is true about Natural Convection?
a) Low heat transfer
b) Due to gravity and natural buoyant forces
c) Dependent on viscosity, density and thermal conductivity
d) All of the mentioned
Answer
Answer: d [Reason:] Natural Convection has low heat transfer. It is due to gravity and natural buoyant forces and, is dependent on viscosity, density and thermal conductivity.
2. _____ is when nucleate boiling transforms to film boiling.
a) Critical temperature
b) Leiden frost point
c) Both of the mentioned
d) None of the mentioned
Answer
Answer: b [Reason:] Leiden frost point is when nucleate boiling transforms to film boiling.
3. Statement 1: Nucleate Boiling is when a layer of film is formed in the beginning.
Statement 2: Boiling starts with the bottom layer which heats up, becomes light and goes up. That way everything becomes hot and there is not temperature difference and hence no heat transfer.
a) True, False
b) True, True
c) False, False
d) False, True
Answer
Answer: d [Reason:] Film Boiling is when a layer of film is formed in the beginning. Boiling starts with the bottom layer which heats up, becomes light and goes up. That way everything becomes hot and there is not temperature difference and hence no heat transfer.
4. Statement 1: When heat transfer takes between a solid surface and a fluid, an insulating film layer is formed. More is the agitation; more is the thickness of the film.
Statement 2: Within the film, the temperature varies from the wall to the temperature of the bulk.
a) True, False
b) True, True
c) False, False
d) False, True
Answer
Answer: d [Reason:] When heat transfer takes between a solid surface and a fluid, an insulating film layer is formed. More is the agitation; lesser is the thickness of the film. Within the film, the temperature varies from the wall to the temperature of the bulk.
5. Statement 1: NPr= (Cp μ)/k
Statement 2: If NPr is lesser than 1, Thermal Boundary layer is thinner than Hydrodynamic Boundary layer.
a) True, False
b) True, True
c) False, False
d) False, True
Answer
Answer: a [Reason:] NPr= (Cp μ)/k. Thermal Boundary layer is thicker than Hydrodynamic Boundary layer.
6. Why is better to use a Jacketed vessel in the dairy industry than a stainless steel container directly?
a) To prevent milk from charring
b) To have a better temperature control
c) The temperature of food in the film = temperature of the wall which is very high. Hence, jacketed vessels are needed
d) All of the mentioned
Answer
Answer: d [Reason:] All the mentioned reasons are corrected.
7. Statement 1: hd/k is _____
Statement 2:_____ is the ratio of convective heat transfer to conductive heat transfer.
a) Prandtl number, Prandtl number
b) Nussel number, Nussel number
c) Pictet number, Pictet number
d) Fourier number, Fourier number
Answer
Answer: b [Reason:] hd/k is Nussel number. Nussel number is the ratio of convective heat transfer to conductive heat transfer.
8. The reciprocal of heat transfer co-efficient is _____
a) Conductance
b) Resistance
c) Density
d) Temperature difference
Answer
Answer: b [Reason:] The reciprocal of heat transfer co-efficient is Resistance.
9. Statement 1: Film-type condensation has a higher heat transfer co-efficient than drop-wise condensation.
Statement 2: Drop-wise condensation is easier to maintain than Film-type condensation
a) True, False
b) True, True
c) False, False
d) False, True
Answer
Answer: c [Reason:] Film-type condensation has a lower heat transfer co-efficient than drop-wise condensation. Film-type condensation is easier to maintain than Drop-wise condensation.
10. Statement 1: Drop-wise condensation takes place on a smooth surface.
Statement 2: All the resistance to heat transfer lies in the film formed during Film-type condensation.
a) True, False
b) True, True
c) False, False
d) False, True
Answer
Answer: d [Reason:] Drop-wise condensation does NOT take place on a smooth surface as the drops cannot adhere to the surface.
Set 2
1. Which of the following sentences is true?
a) Direct heating has higher heat transfer rates than indirect heating
b) Indirect heating has higher heat transfer rates than direct heating
c) Both of them have the same heat transfer rates
d) Cannot be determined
Answer
Answer: a [Reason:] Direct heating has higher heat transfer rates than indirect heating.
2. If ___(1)__ heating has higher heat transfer rates than ___(2)__ heating, then why is (1) difficult to be used
a) Direct, Indirect, no difficulty, they’re used
b) Direct, Indirect, coil is difficult to clean and is prone to bacterial growth
c) Indirect, Direct, no difficulty, they’re used
d) Indirect, Direct, coil is difficult to clean and is prone to bacterial growth
Answer
Answer: b [Reason:] Direct heating has higher heat transfer rates than indirect heating, but, the coil is difficult to clean and is prone to bacterial growth.
3. In a jacketed vessel, the only way to increase the heat transfer rates is to increase the temperature difference.
a) True
b) False
Answer
Answer: a [Reason:] In a jacketed vessel, the only way to increase the heat transfer rates is to increase the temperature difference.
4. Which of the following is an advantage of using pumps as heat transfer equipment?
a) No stirrer required
b) Taking them to a heat exchanger where the area used for heat transfer can be easily changed
c) Both of the mentioned
d) None of the mentioned
Answer
Answer: c [Reason:] Both the mentioned statements are true.
5. External heat exchangers are gaining popularity as they’ve several advantages over conventional methods. Still, there is a major drawback. Which among the following is it?
a) Some shear-sensitive cells might get damaged due to abrasion
b) It is difficult for pumps to withstand high temperature without leakages of the fluid
c) Both of the mentioned
d) None of the mentioned
Answer
Answer: c [Reason:] External heat exchangers are gaining popularity as they’ve several advantages over conventional methods. Still, there are drawbacks like some shear-sensitive cells might get damaged due to abrasion. Also, it is difficult for pumps to withstand high temperature without leakages of the fluid.
6. Which of the following is a parameter to be checked before choosing the shape of the pitch in heat exchangers?
a) Easiness to clean
b) High heat transfer
c) Cost
d) All of the mentioned
Answer
Answer: d [Reason:] All of the mentioned are valid reasons.
7. Statement 1: Difference between 1-1 and 1-2 heat exchanger is that 1-2 has both counter AND co current, whereas 1-1 has only co-current.
Statement 2: 1-2 heat exchanger requires a high pressure drop.
a) True, False
b) True, True
c) False, False
d) False, True
Answer
Answer: b [Reason:] Both the statements pertaining to heat exchangers are true.
8. Statement 1: Generally, in small scaled jacketed pans, food products like jams, sauces etc are made.
Statement 2: Baffles provide structural support to tubes, but they cannot prevent channeling.
a) True, False
b) True, True
c) False, False
d) False, True
Answer
Answer: a [Reason:] Generally, in small scaled jacketed pans, food products like jams, sauces etc are made. Baffles provide structural support to tubes and prevent channeling also.
9. Statement 1: Scraping improves heat transfer co-efficient by 5 times in case of non-Newtonian fluids.
Statement 2: In food industry, major physical changes to food items when they’re processed, take place like transformation from Newtonian to Non-Newtonian fluids. Hence, scraped surface heat exchangers are very beneficial.
a) True, False
b) True, True
c) False, False
d) False, True
Answer
Answer: b [Reason:] Both the statements are true.
10. Which of the following is untrue about scraped surface heat exchangers?
a) They’re unsuitable for viscous fluids
b) They’re suitable for fouling fluids
c) They’re used for continuous operation and have a double pipe
d) None of the mentioned
Answer
Answer: a [Reason:] Scraped surface heat exchangers are suitable for viscous fluids.
11. Which of the following heat exchangers are used for quick exchange of heat?
a) Shell and tube heat exchangers
b) Plate heat exchangers
c) Scraped surface heat exchangers
d) Jacketed Vessels
Answer
Answer: b [Reason:] Plate heat exchangers are used for quick exchange of heat.
12. Statement 1: Plate heat exchangers are used in heat sensitive foods like milk.
Statement 2: Principle behind plate heat exchangers is that there is very less space between the plates and hence quick heating can take place.
a) True, False
b) True, True
c) False, False
d) False, True
Answer
Answer: b [Reason:] Both the statements are true.
13. Which of the following is true about Plate heat exchangers?
a) They’re used for Ultra high temperature treatment
b) Used for high temperature and short time
c) Both of the mentioned
d) None of the mentioned
Answer
Answer: c [Reason:] Plate heat exchangers are used for Ultra high temperature treatment (UHT) and for High temperature and short time (HTST).
14. Contamination takes place to high extend in Plate heat exchangers.
a) True, the space between plates is too less
b) False, they cannot be used for viscous liquids
c) Cannot be determined
d) True, they can be used for thin liquids only
Answer
Answer: a [Reason:] The space between plates, in a Plate heat exchanger is too less.
15. Statement 1: In coiled heat exchanger, the coils can be present inside and outside the vessel.
Statement 2: The coils can have either hot/cold fluid present inside them or even electrical coils can be present.
a) True, False
b) True, True
c) False, False
d) False, True
Answer
Answer: b [Reason:] Both the statements are true.
Set 3
1. Statement 1: Radiation is the transfer of heat by electromagnetic waves.
Statement 2: When heat is radiated from a hot source, the amount of heat received by the body depends on the nature of the body.
a) True, False
b) True, True
c) False, False
d) False, True
Answer
Answer: b [Reason:] Radiation is the transfer of heat by electromagnetic waves. When heat is radiated from a hot source, the amount of heat received by the body depends on the nature of the body. E.g.: A black body will absorb more energy than any other body from the same source which is exposed to both the bodies in the same manner.
2. Statement 1: Radiation needs a medium to travel.
Statement 2: Thermal radiation takes place at a certain temperature for every body.
a) True, False
b) True, True
c) False, False
d) False, True
Answer
Answer: c [Reason:] Radiation needs NO medium to travel. Thermal radiation is emitted by every body at a temperature above 0 K.
3. Statement 1: Radiation is NOT heat.
Statement 2: Maximum value of absorptivity is 1.
a) True, False
b) True, True
c) False, False
d) False, True
Answer
Answer: b [Reason:] Radiation is NOT heat, and if it is absorbed and converted to heat, it is no longer heat. Maximum value of absorptivity is 1.
4. The emission of radiation by any body is independent of the radiation by any body next to it.
a) True
b) False
Answer
Answer: a [Reason:] The emission of radiation by any body is independent of the radiation by any body next to it.
5. A food industry keeps food cool in a very crude manner, by radiation. It paints its walls white and not black, because of _____
a) Kirchhoff’s Law
b) Stephan-Boltzmann Law
c) None of the mentioned
d) Both of the mentioned
Answer
Answer: a [Reason:] Kirchhoff’s law states that at temperature equilibrium, the absorptivity of a grey body is equal to its emissivity. Since white paint has less emissivity than that of black paint, the wall is painted white.
6. Which of the following reason does NOT affect radiation between two parallel bodies?
a) Angle of vision
b) Orientation of surfaces
c) Emissivity of both
d) Smoothness and roughness
Answer
Answer: a [Reason:] The angle of vision does not affect radiation between two parallel bodies. But, it is an important factor when it comes to curved surfaces.
7. Freezer is at -18 deg C. Will will be Radiative heat transfer if meat is at 298k, its emissivity is 0.82 and average area is 0.045m2.
Either use Stefan Boltzmann law or take hr (radiative heat transfer co-efficient) as 0.227.
ε= ( Tav/100 )3
a) 7.61
b) 6.94
c) 8.43
d) None of the mentioned
Answer
Answer: a [Reason:] Stefan Boltzmann law:
T1 = 298, T2 = 255. σ= 5.67*10-8 W /m2K4
T14 = 7.88 * 109
T24 = 4.22* 109
Using, q = A εσ (T14 – T24)
q = 5.7 * 10-8 * 0.82* 0.45 * (7.88-4.22) * 109 = 7.61.
Tav= (298 + 255) /2
hr = 3.93 W/m2 K
q = A εσ (T1 -T2) = 3.93* 0.045 * (298-255) = 7.61.
8. Statement 1: Radiation dryers are used to dry grains and reduce their moisture content before storage.
Statement 2: Baking ovens are used both for making dough and after that’s made, making biscuits by cutting them and baking them further. This entire process uses radiation.
a) True, False
b) True, True
c) False, False
d) False, True
Answer
Answer: b [Reason:] Both the statements pertaining to radiation are true.
9. In deep freezers, the walls absorb heat from food materials by _____ and keep them cool.
a) Conduction
b) Convection
c) Radiation
d) None of the mentioned
Answer
Answer: c [Reason:] In deep freezers, the walls absorb heat from food materials by radiation and keep them cool.
10. Radiation dryers use_____
a) Ultraviolet rays
b) Infrared radiation
c) Visible range
d) None of the mentioned
Answer
Answer: b [Reason:] Radiation dryers use Infrared radiation.
Set 4
1. Metabolism is a source of water.
a) True
b) False
Answer
Answer: d [Reason:] Water is by-product of Metabolism.
2. Which of the following is the general formula for carbohydrates?
a) Cm(H2o)n
b) Cm+1(H2o)n
c) Cm(H2o)n+1
d) Cm-1(H2o)n
Answer
Answer: a [Reason:] Cm(H2o)n is the formula for Carbohydrates.
3. Oligosaccharides are called Sugars
a) True
b) False
Answer
Answer: b [Reason:] Mono and disaccharides(Low molecular weight) are called sugars.
4. Which of the following is not a function of Carbohydrates?
a) Storage of energy
b) Fuel for metabolism
c) Structural components
d) None of the mentioned
Answer
Answer: d [Reason:] Carbohydrates store energy (starch/glycogen) , are a fuel for metabolism-glucose and are structural components- cellulose.
5. Mina is a diabetics patience. One day she is tempted to eat junk food. Which is a relatively a better food product to eat – pasta or candy? Why?
a) Pasta- contains primary carbohydrates which increases blood sugar level comparatively slowly and to a lesser level
b) Pasta- contains secondary carbohydrates which increases blood sugar level comparatively slowly and to a lesser level
c) Candy – contains primary carbohydrates which increases blood sugar level comparatively slowly and to a lesser level
d) Candy- contains secondary carbohydrates which increases blood sugar level comparatively slowly and to a lesser level
Answer
Answer: b [Reason:] Pasta contains secondary carbohydrates which increases blood sugar level comparatively slowly and to a lesser level.
6. More than 50-55% of carbohydrates consumption is needed daily.
a) True
b) False
Answer
Answer: b [Reason:] Only 50-55% of carbohydrates consumption is needed daily.
7. Sham is over-weight. Which of the following carbohydrates is he consuming maximum?
a) Refined
b) Unrefined
c) Glycogen
d) None of the mentioned
Answer
Answer: a [Reason:] Refined carbohydrates are the carbohydrates that are highly processed. Hence they’re stripped off of the initial minerals although the number of calories remain constant.
8. This carbohydrate is used during intense exercising. Which among the following is it?
a) Starch
b) Sucrose
c) Fructose
d) Glycogen
Answer
Answer: d [Reason:] Glycogen is stored in the liver by the body and used during intense exercising.
9. Which of the following is correct?
a) Sucrose is made of galactose and glucose
b) Lactose is made up of glucose and fructose
c) Lactose is made up of galactose and fructose
d) Sucrose is made up of glucose and fructose
Answer
Answer: d [Reason:] Sucrose is made up of glucose and fructose.
10. Fruits contain fructose which is a primary carbohydrate. These increase the blood sugar level. Why are fruits still recommended to be eaten?
a) They have exceptionally low Glycemic Index
b) They have exceptionally highly Glycemic Index
c) They’re secondary carbohydrates
d) None of the mentioned
Answer
Answer: a [Reason:] There are certain exceptions to the Glycemic Index. Fruits are one of them. It is low for fruits.
11. What is Glycemic Index of carbohydrates?
a) It shows which other nutrient it is being ingested with
b) It shows how quickly a carbohydrate is digested
c) It shows how quickly a carbohydrate increases blood sugar level
d) None of the mentioned
Answer
Answer: c [Reason:] Glycemic Index shows how quickly a carbohydrate increases blood sugar level.
Set 5
1. Which of the following is not an objective of annealing?
a) Softening of steel
b) Hardening of steel
c) Increase ductility
d) Relieve internal stress
Answer
Answer: b [Reason:] Among the many purposes of treating the steel through annealing is softening of steel, hardening of steel and relieving the internal stresses, but annealing is not used for hardening of the steel.
2. In full annealing, the steel is heated at what temperature?
a) Above critical temperature
b) Above vaporization temperature
c) Above liquefying temperature
d) Above solidification temperature
Answer
Answer: a [Reason:] In the process of full annealing, the steel has to be heated slightly above the critical temperature. At this point, the steel has to be held for a considerable amount of time.
3. In annealing process, for the formation of hypereutectoid steel, the steel has to be heated above what point?
a) Ac1
b) Ac2
c) Ac3
d) Ac4
Answer
Answer: a [Reason:] For the formation of hypereutectoid steel, in annealing process, the steel has to be heated above the Ac1 point, which is the lower critical line in the temperature versus carbon content graph.
4. In annealing process, for the formation of hypoeutectoid steel, the steel has to be heated above what point?
a) Ac1
b) Ac2
c) Ac3
d) Ac4
Answer
Answer: c
5. For how long is the heated steel held in full annealing process?
a) 1 minute
b) 3 minutes
c) 6 minutes
d) 9 minutes
Answer
Answer: b [Reason:] The heated steel is held at the critical temperature for about 3 to 4 minutes. By doing this, the steel gets enough time to make the internal changes desired.
6. In full annealing, the metal cannot be buried in which of the following materials?
a) Sand
b) Lime
c) Ashes
d) Manganese powder
Answer
Answer: d [Reason:] In the process, full annealing, if the metal is removed at high temperatures, they need to be buried. For this, the material cannot be manganese powder.
7. Annealing is a fast process.
a) True
b) False
Answer
Answer: b [Reason:] Annealing is considered to be a very slow process, as the part where the steel is cooled, takes up a lot of time for the process to get completed.
8. Which of the following is also called as diffusion annealing?
a) Isothermal annealing
b) Process annealing
c) Homogenizing
d) Spheroidise annealing
Answer
Answer: c [Reason:] Homogenising has another name as diffusion annealing. This method is applied to both the ingots, carbon as well as alloy steel.
9. At what temperature is homogenizing carried out?
a) 1150°C
b) 1370°C
c) 1420°C
d) 1320°C
Answer
Answer: a [Reason:] Homogenizing is carried out between temperature ranges of 1100°C to 1200°C, but the most optimum temperature is 1150°C, at which the diffusion process goes ahead smoothly.
10. Normalizing process takes lot of time to complete.
a) True
b) False
Answer
Answer: b [Reason:] Normalizing is a comparatively faster process than annealing, as in this process, the cooling rate is supposed to be very high, causing the process to end in lesser time.