MCQOPTIONS
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MCQOPTIONS
This section includes 253 Mcqs, each offering curated multiple-choice questions to sharpen your Heat Transfer (HT) knowledge and support exam preparation. Choose a topic below to get started.
| 151. |
Water is normally used as a coolant in the heat exchange equipments mainly because of its |
| A. | Abundance & high heat capacity |
| B. | Low density |
| C. | Low viscosity |
| D. | High fluidity |
| Answer» B. Low density | |
| 152. |
Cork is a good insulator because |
| A. | It is porous |
| B. | Its density is low |
| C. | It is flexible |
| D. | It can be powdered |
| E. | It can be cast into rolls |
| Answer» B. Its density is low | |
| 153. |
Which one of the following is a very good insulator? |
| A. | A hard wood board |
| B. | A porcelain sheet |
| C. | An asbestos sheet |
| D. | Saw dust |
| E. | None of the above |
| Answer» E. None of the above | |
| 154. |
There are two spheres of copper the ratio of their radii being 1 : 3 both at the same temperature. The ration of heat contents will be |
| A. | 1 ; 81 |
| B. | 1 ; 9 |
| C. | 1 ; 3 |
| D. | 1 ; 1 |
| E. | 1 ; 27 |
| Answer» F. | |
| 155. |
The ratio of specific heats of a gas is 1.4 and the value of specific heat at constant pressure is 7.0 cal/mole ?C. The difference between specific heat at constant presure and specific heat at constant volume will be |
| A. | 1.4 |
| B. | 5 |
| C. | 1/1.4 |
| D. | 1.7 |
| E. | 2 |
| Answer» F. | |
| 156. |
The statement that the emissivity and absorptivity of a surface is surrounded by its own temperature are the same for both monochromatic and total radiation, is known as |
| A. | Kirchhoff's law |
| B. | Lambert law |
| C. | Stefan Boltzman low |
| D. | D'Alembert's rule |
| E. | Law of emissivity |
| Answer» B. Lambert law | |
| 157. |
Which of the following is an example of absorption? |
| A. | Extraction of sugarcane juice |
| B. | Dechlorination of water |
| C. | Removal of oil from cake |
| D. | Removal of moisture from gasoline |
| E. | None of the above |
| Answer» E. None of the above | |
| 158. |
Essential requirement for the transfer of heat from one body to another is |
| A. | Both bodies must be solids |
| B. | Both bodies must be in contact |
| C. | Temperatures of the two bodies must be different |
| D. | One of the bodies must have internal source of heat generation |
| E. | All of the above |
| Answer» D. One of the bodies must have internal source of heat generation | |
| 159. |
The wagelength of X-rays is |
| A. | 6 to 100000 micron |
| B. | 0.4 to 0.8 micron |
| C. | 0.8 to 400 micron |
| D. | 0.1 to 0.4 micron |
| E. | 0.014 to 0.018 micron |
| Answer» B. 0.4 to 0.8 micron | |
| 160. |
A fur coat on an animal will help the animal to be |
| A. | Warm in summer |
| B. | Safe in rains |
| C. | Cool in summer |
| D. | Warm in winter |
| E. | Cool in winter |
| Answer» E. Cool in winter | |
| 161. |
A body cools from 80?C to 70?C in 10 minutes. The time taken by the body for further cooling to 60?C will be |
| A. | 5 minutes |
| B. | 7 minutes |
| C. | 10 minutes |
| D. | More than 10 minutes |
| E. | Less than 10 minutes |
| Answer» E. Less than 10 minutes | |
| 162. |
Which one of the following cannot be unit of thermal conductivity? |
| A. | Kcal/m-hr?C |
| B. | cal/c,-sec?K |
| C. | BTU/ft-h?F |
| D. | CHU/ft-hr?C |
| E. | Watt / m2 K |
| Answer» F. | |
| 163. |
A shpere, a cube and a disc all of the same material, quality and volume are heated to 900K and left in air. Which of these will have the lowest rate of cooling |
| A. | Sphere |
| B. | All will have the same rate of cooling |
| C. | Disc |
| D. | Cube |
| E. | 37,500 kg |
| Answer» B. All will have the same rate of cooling | |
| 164. |
If thermal conductivity of a material of wall varies as ko (1 - ?t ). The temperature at the centre of the wall will be |
| A. | Same as in case of constant thermal conductivity |
| B. | More than that in case of constant thermal conductivity |
| C. | Less than that in case of constant thermal conductivity |
| D. | Depends on other factors |
| E. | None of the above |
| Answer» D. Depends on other factors | |
| 165. |
For glass wool the thermal conductivity varies from sample to sample because of variations in |
| A. | Structure |
| B. | Composition |
| C. | Density |
| D. | Porosity |
| E. | All of the above |
| Answer» F. | |
| 166. |
Which dimensionless number can be used for convective heat transfer? |
| A. | Mach number |
| B. | 37,500 kg |
| C. | Graetz number |
| D. | Froude number |
| E. | Nusselt number |
| Answer» F. | |
| 167. |
The sensible heat of hot industrial gases can be recovered by a |
| A. | Regenerator |
| B. | Recuperator |
| C. | Either of (A) and (B) above |
| D. | None of the above |
| E. | None of the above |
| Answer» D. None of the above | |
| 168. |
The overall co-efficient of heat transfer is expressed as |
| A. | kcal/hr |
| B. | kcal/m/hr |
| C. | kcal/m2/hr/?C |
| D. | None of the above |
| E. | Nichrome |
| Answer» D. None of the above | |
| 169. |
Emissivity and absorptivity of a surface are equal for radiation |
| A. | 37,500 kg |
| B. | in ultraviolet region |
| C. | in radio frequency range |
| D. | with equal temperature and wavelength |
| E. | infrared region |
| Answer» E. infrared region | |
| 170. |
The face temperatures of a flat wall are 650?C and 450?C respectively and the thermal conductivity of wall material is 0.30 kcal/m-hr-?C. For a wall thickness of 20 cm, the rate of heat conduction per square meter of wall area will be |
| A. | 37,500 kg |
| B. | 300 kcal/hr |
| C. | 600 kcal/hr |
| D. | 3000 kcal/hr |
| E. | 150 kcal/hr |
| Answer» C. 600 kcal/hr | |
| 171. |
Calorific value of Indian coal is |
| A. | 5700 kcal/kg |
| B. | 9600 kcal/kg |
| C. | Nichrome |
| D. | 3300 kcal/kg |
| E. | 2000 kcal/kg |
| Answer» E. 2000 kcal/kg | |
| 172. |
Four balls made of lead, glass, brass and iron made of same size, are heated to 100?C. They are simultaneously placed on a sheet of paraffin nearly 5 mm thick. Which ball will drop first? |
| A. | Lead |
| B. | Glass |
| C. | 37,500 kg |
| D. | Iron |
| E. | Brass |
| Answer» E. Brass | |
| 173. |
The equation ?m x T = constant represents |
| A. | Wein's Law |
| B. | Kirchhoff's law |
| C. | Stefan Boltzmann's law |
| D. | None of the above |
| E. | Nichrome |
| Answer» B. Kirchhoff's law | |
| 174. |
The reflectance of a black body is |
| A. | less than 1.0 |
| B. | 37,500 kg |
| C. | infinite |
| D. | one |
| E. | zero |
| Answer» F. | |
| 175. |
Tea pots are highly polished |
| A. | So that they may not conduct heat from outside |
| B. | So that they may absorb all radiation from outside |
| C. | To make them attractive to look at |
| D. | Because porcelain takes high polish |
| E. | None of the above |
| Answer» C. To make them attractive to look at | |
| 176. |
Dynamic similarity is the similarity of |
| A. | Shape |
| B. | Forces |
| C. | Velocities |
| D. | Effective dimensions |
| E. | None of the above |
| Answer» C. Velocities | |
| 177. |
Radiation heats transfer between two surfaces can be reduced by |
| A. | Preheating the surfaces closer together |
| B. | Introducing radiation shield between the surfaces |
| C. | Polishing the surface |
| D. | 37,500 kg |
| E. | Bringing the surfaces closer together |
| Answer» C. Polishing the surface | |
| 178. |
The dimensions of specific heat are |
| A. | LT?2 |
| B. | LT-2?-1 |
| C. | LT-2? |
| D. | LT-1?-1 |
| E. | 37,500 kg |
| Answer» C. LT-2? | |
| 179. |
All temperatures above the freezing point of gold are usually determined by |
| A. | Thermo couple |
| B. | Gas thermometer |
| C. | Optical pyrometer |
| D. | Resistance bridge |
| E. | Any of the above |
| Answer» D. Resistance bridge | |
| 180. |
Two large closely spaced concentric spheres (both of which are perfect black body radiators) are maintained at temperatures of 127?C and 27?C respectively. The space in between the two spheres is evacuated. Taking Stefan Boltzmann constant as 5.67 x 108 watt m2K the rate of radiation in watts per sq. m between the two spheres is approximately |
| A. | 992 |
| B. | 762 |
| C. | 37,500 kg |
| D. | 852 |
| E. | 666 |
| Answer» B. 762 | |
| 181. |
In a thermal power plant, cooling towers are used to cool |
| A. | steam |
| B. | condensed wate |
| C. | circulating |
| D. | All of the above |
| E. | 37,500 kg |
| Answer» D. All of the above | |
| 182. |
In constant volume Hydrogen gas Thermometer, a correction has to be applied, because |
| A. | Hydrogen is impure |
| B. | Expansion of Hydrogen is non-linear |
| C. | Density of mercury changes |
| D. | None of the above |
| E. | Optical pyrometer |
| Answer» C. Density of mercury changes | |
| 183. |
The wavelength for maximum emissive power is given by |
| A. | Stefan Boltzman's law |
| B. | Wein's law |
| C. | Fourier's law |
| D. | Kirchhoff's law |
| E. | Planck's law |
| Answer» C. Fourier's law | |
| 184. |
Maximum heat transfer rate can be expected in case of |
| A. | Turbulent flow |
| B. | Co-current flow |
| C. | Laminar flow |
| D. | Counter current flow |
| E. | Heat transfer rate is independent of nature of flow |
| Answer» B. Co-current flow | |
| 185. |
Unsaturated vapours |
| A. | Do not obey gas laws |
| B. | Obey Boyle's law and not Boyles law |
| C. | Fully obey gas laws |
| D. | Superheated vapour |
| E. | Partly obey gas laws depending upon the degree of unsaturation |
| Answer» B. Obey Boyle's law and not Boyles law | |
| 186. |
An isotherm is a graph |
| A. | Showing pressure volume changes at constant temperature |
| B. | Connecting points of equal pressure |
| C. | Constant temperature |
| D. | Connecting points of equal temperature |
| E. | Showing product of pressure and volume against pressure |
| Answer» B. Connecting points of equal pressure | |
| 187. |
The emissivity of a body will be equal to absorptivity when |
| A. | Body is in thermal equilibrium |
| B. | Temperature of body is rising |
| C. | Temperature of body is falling |
| D. | Body is at low temperature |
| E. | Body is at high temperature |
| Answer» B. Temperature of body is rising | |
| 188. |
The mass of water vapour per kg of the pressure of saturated vapour at the air is known as |
| A. | Specific humidity |
| B. | Relative humidity |
| C. | Molar humidity |
| D. | Humidity ratio |
| E. | None of the above |
| Answer» B. Relative humidity | |
| 189. |
All substances emit radiation, the quality and quantity depending upon the absolute temperature and the properties of the material composing the radiating body. The above statement is known as the statement of |
| A. | Stefan-Bolzmann's law |
| B. | Kirchhoff's law |
| C. | Planck's law |
| D. | D Alambert's rule |
| E. | Law of radiation |
| Answer» D. D Alambert's rule | |
| 190. |
A piece of metal with a circular hole is heated. If the metal expands on heating the diameter of the hole will |
| A. | Increase |
| B. | Decrease |
| C. | Increase or decrease depending upon the diameter of the whole |
| D. | Increase or decrease depending on the kind of the metal |
| E. | None of the above |
| Answer» B. Decrease | |
| 191. |
The value of Stefan Boltzmann's constant in kcal-m2-hr-k4 is |
| A. | 0.174 x 10-8 |
| B. | 0.567 x 10-4 |
| C. | 4.87 x 10-8 |
| D. | 56.7 x 10-9 |
| E. | 1.335 x 10-12 |
| Answer» D. 56.7 x 10-9 | |
| 192. |
The rate of heat flow from a 50 mm thick wall of material having thermal conductivity of 40 W/m?C for a temperature difference of 10?C will be |
| A. | 800 W/m2 - hr |
| B. | 200 W/m2 - hr |
| C. | 2000 W/m2 - hr |
| D. | 80 W/m2 - hr |
| E. | 8000 W/m2 - hr |
| Answer» F. | |
| 193. |
A body cools from 90?C to 80?C in 5 minutes. Under the same external conditions to cool from 80?C to 70?C the body will take |
| A. | 2.5 minutes |
| B. | Cannot be predicted |
| C. | 5 minutes |
| D. | More than 5 minutes |
| E. | 4 minutes |
| Answer» E. 4 minutes | |
| 194. |
Pipes are insulated so that |
| A. | There is minimum corrosion |
| B. | Heat loss from the surface is minimized |
| C. | They can withstand higher fluid pressures |
| D. | Vibrations resulting from fluid flow are minimized |
| E. | They may not break under pressure |
| Answer» C. They can withstand higher fluid pressures | |
| 195. |
Kinematic viscosity indicates |
| A. | heat energy transport through conduction |
| B. | 37,500 kg |
| C. | heat evergy transport through convection |
| D. | conversion of momentum into heat energy |
| E. | momentum transport by molecular friction |
| Answer» F. | |
| 196. |
Four rods with different radii 'r' and length 'l' are used to connect to reservoirs of heat at different temperature. Which one of them with conduct most heat? |
| A. | r = 1 cm, l = 1m |
| B. | r = 2 cm, l = |
| C. | r = 2 cm, l = 2m |
| D. | r = |
| E. | 37,500 kg |
| Answer» C. r = 2 cm, l = 2m | |
| 197. |
A non-dimensional number which generally finds application in mass transfer problems is |
| A. | Stanton number |
| B. | Weber number |
| C. | Grashoff number |
| D. | Mach number |
| E. | Graetz number |
| Answer» B. Weber number | |
| 198. |
The average value of thermal conductivity for water at 20?C is about |
| A. | 0.13 |
| B. | 0.32 |
| C. | 0.51 |
| D. | None of the above |
| E. | Nichrome |
| Answer» D. None of the above | |
| 199. |
The value of thermal conductivity of water at room temperature is expected to be |
| A. | 0.05 kcal/m-hr-?C |
| B. | 0.5 kcal/m-hr-?C |
| C. | 0.001 kcal/m-hr-?C |
| D. | 1.0 kcal/m-hr-?C |
| E. | 1.5 kcal/m-hr-?C |
| Answer» C. 0.001 kcal/m-hr-?C | |
| 200. |
A dimensionless heat transfer coefficient which gives a measure of the ratio of the heat transfer rate to the rate at which heat would be conducted within the fluid under a temperature gradient is known as |
| A. | Stanton number |
| B. | Reynolds number |
| C. | Nusselt number |
| D. | Grashoff number |
| E. | Peclet number |
| Answer» D. Grashoff number | |