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MCQOPTIONS
This section includes 248 Mcqs, each offering curated multiple-choice questions to sharpen your Thermodynamics knowledge and support exam preparation. Choose a topic below to get started.
| 151. |
The crank radius of a single-cylinder IC engine is 60 mm and the diameter of the cylinder is 80 mm. The swept volume of the cylinder in cm |
| A. | 48 |
| B. | 96 |
| C. | 302 |
| D. | 603 |
| Answer» E. | |
| 152. |
In an air-standard Otto cycle, the compression ratio is 10. The condition at the beginning of the compression process is 100 kPa and 27 C. Heat added at constant volume is 1500 kJ/kg, while 700 kJ/kg of heat is rejected during the other constant volume process in the cycle. Specific gas constant for air = 0.287 kJ/kgK. The mean effective pressure (in kPa) of the cycle is |
| A. | 103 |
| B. | 310 |
| C. | 515 |
| D. | 1032 |
| Answer» E. | |
| 153. |
The values of enthalpy of steam at the inlet and outlet of a steam turbine in a Rankine cycle are 2800 kJ/kg and 1800 kJ/kg respectively. Neglecting pump work, the specific steam consumption in kg/kW hour is |
| A. | 3.60 |
| B. | 0.36 |
| C. | 0.06 |
| D. | 0.01 |
| Answer» B. 0.36 | |
| 154. |
Assume the above turbine to be part of a simple Rankine cycle. The density of water at the inlet to the pump is 1000 kg/m3. Ignoring kinetic and potential energy effects, the specific work (in kJ/kg) supplied to the pump is |
| A. | 0.293 |
| B. | 0.351 |
| C. | 2.930 |
| D. | 3.510 |
| Answer» D. 3.510 | |
| 155. |
If mass flow rate of steam through the turbine is 20 kg/s, the power output of the turbine (in MW) is |
| A. | 12.157 |
| B. | 12.941 |
| C. | 168.001 |
| D. | 168.785 |
| Answer» B. 12.941 | |
| 156. |
In a Rankine cycle, the enthalpies at turbine entry and outlet are 3159 kJ/kg and 2187 kJ/ kg, respectively. If the specific pump work is 2 kJ/kg, the specific steam consumption (in kg/ kWh) of the cycle based on net output is. |
| A. | 4.7815 kg/kW.h |
| B. | 3kg/kW.h |
| C. | 3.7815 kg/kW.h |
| D. | 6 kg/kW.h |
| Answer» D. 6 kg/kW.h | |
| 157. |
Steam with specific enthalpy (h) 3214 kJ/kg enters an adiabatic turbine operating at steady state with a flow rate 10 kg/s. As it expands, at a point where his 2920 kJ/kg, 1.5 kg/s is extracted for heating purposes. The remaining 8.5 kg/s further expands to the turbine exit, where h = 2374 kJ/kg. Neglecting changes in kinetic and potential energies, the net power output (in kW) of the turbine is_____. |
| A. | 65581 kW |
| B. | 7589 kW |
| C. | 7581 kW |
| D. | 7500 kW |
| Answer» D. 7500 kW | |
| 158. |
For a gas turbine power plant, identify the correct pair of statements. P. Smaller in size compared to steam power plant for same power output Q. Starts quickly compared to steam power plant R. Works on the principle of Rankine cycle S. Good compatibility with solid fuel |
| A. | P and Q |
| B. | R and S |
| C. | Q and R |
| D. | P and S |
| Answer» B. R and S | |
| 159. |
In an ideal Brayton cycle, atmospheric air (ratio of specific heats, c |
| A. | m = 18.07 kg/s. |
| B. | m = 108.07 kg/s. |
| C. | m = 1007 kg/s. |
| D. | m = 108kg/s. |
| Answer» C. m = 1007 kg/s. | |
| 160. |
An ideal Brayton cycle, operating between the pressure limits of 1 bar and 6 bar, has minimum and maximum temperatures of 300 K and 1500 K. The ratio of specific heats of the working fluid is 1.4. The approximate final temperature in Kelvin at the end of the compression and expansion processes are respectively |
| A. | 500 and 900 |
| B. | 900 and 500 |
| C. | 500 and 5400 |
| D. | 900 and 900 |
| Answer» B. 900 and 500 | |
| 161. |
A small steam whistle (perfectly insulated and doing no shaft work) causes a drop of 0.8 kJ/kg in enthalpy of steam from entry to exit. If the kinetic energy of the steam at entry is negligible, the velocity of the steam at exit is |
| A. | 4 m/s |
| B. | 40 m/s |
| C. | 80 m/s |
| D. | 120 m/s |
| Answer» C. 80 m/s | |
| 162. |
Consider a simple gas turbine (Brayton) cycle and a gas turbine cycle with perfect regeneration. In both the cycles, the pressure ratio is 6 and the ratio of the specific heats of the working medium is 1.4. The ratio of minimum to maximum temperatures is 0.3 (with temperatures expressed in K) in the regenerative cycle. The ratio of the thermal efficiency of the simple cycle to that of the regenerative cycle is._____. |
| A. | 4.5453 |
| B. | 3.4557 |
| C. | 2 |
| D. | 0.8021 |
| Answer» E. | |
| 163. |
A system undergoes a State change from 1 to 2.According to the second law of thermodynamics, for the process to be feasible, the entropy change, S |
| A. | is positive or zero |
| B. | is negative or zero |
| C. | is zero |
| D. | can be positive, negative or zero |
| Answer» E. | |
| 164. |
Consider a refrigerator and a heat pump working on the reversed Carnot cycle between the same temperature limits. Which of the following is correct? |
| A. | COP of refrigerator = COP of heat pump |
| B. | COP of refrigerator = COP of heat pump + 1 |
| C. | COP of refrigerator = COP of heat pump 1 |
| D. | COP of refrigerator = Inverse of the COP of heat pump |
| Answer» D. COP of refrigerator = Inverse of the COP of heat pump | |
| 165. |
For a single stage impulse turbine with rotor diameter of 2 m and a speed of 3000 rpm when the nozzle angle is 20 , the optimum velocity of steam in m/s is |
| A. | 334 |
| B. | 356 |
| C. | 668 |
| D. | 711 |
| Answer» D. 711 | |
| 166. |
A steam turbine operating with less moisture is _____(more/less) efficiency and _____ (less/ more) prone to blade damage. |
| A. | more more, less |
| B. | less , more more, |
| C. | Less, |
| D. | Less, more more, less |
| Answer» E. | |
| 167. |
Velocity compounded steam turbine known as _____ (curtis/rateau) turbine uses the principle of converting entire _______(pressure/velocity) energy before entering the first stage runner itself. |
| A. | Curtis |
| B. | Curtis Pressure |
| C. | Pressure |
| D. | Pressure Curtis |
| Answer» C. Pressure | |
| 168. |
An economizer in a steam generator performs the function of |
| A. | Preheating the combustion air |
| B. | Preheating the feed water |
| C. | Preheating the input fuel |
| D. | Raising the temperature of steam |
| Answer» C. Preheating the input fuel | |
| 169. |
A gas turbine with air as the working fluid has an isentropic efficiency of 0.70 when operating at a pressure ratio of 3. Now, the pressure ratio of t he t ur bi ne i s i ncr eased t o 5, whi l e maintaining the same inlet conditions. Assume air as a perfect gas with specific heat ratio = 1.4. I f the specific work output remains the same for both the cases, the isentropic efficiency of t he t ur bi ne at t he pr essur e r at i o of 5 is___(round off to two decimal places). |
| A. | 5 |
| B. | 7 |
| C. | 0.51 |
| D. | 1 |
| Answer» D. 1 | |
| 170. |
An engine working on air standard Otto cycle is supplied with air at 0.1 MPa and 35 C. The compression ratio is 8. The heat supplied is 500 kJ/kg. Property data for air: c |
| A. | 1405 |
| B. | 1503.98 |
| C. | 1403.98 |
| D. | 1403 |
| Answer» D. 1403 | |
| 171. |
Air enters a diesel engine with a density of 1.0 kg/m |
| A. | 625 |
| B. | 525 |
| C. | 535 |
| D. | 520 |
| Answer» C. 535 | |
| 172. |
Group-I shows different heat addition processes in power cycles. Likewise, Group-II shows different heat removal processes. GroupIII lists power cycles. Match items from Groups I, II and III. |
| A. | P S 5, R U 3, P S 1, Q T 2 |
| B. | P S 1, R U 3, P S 4, P T 2 |
| C. | R T 3, P S 1, P T 4, Q S 5 |
| D. | P T 4, R S 3, P S 1, P S 5 |
| Answer» C. R T 3, P S 1, P T 4, Q S 5 | |
| 173. |
Determine the correctness or otherwise Assertion (A) and the Reason (R). |
| A. | Both (A) and (R) are true and (R) is the correct reason for (A) |
| B. | Both (A) and (R) are true but (R) is NOT the correct reason for (A) |
| C. | Both (A) and (R) are false |
| D. | (A) is false but (R) is true |
| Answer» B. Both (A) and (R) are true but (R) is NOT the correct reason for (A) | |
| 174. |
A steam turbine receives steam steadily at 10 bar with a enthalpy of 3000 kJ/kg and discharges at 1 bar with an enthalpy of 2700 kJ/kg. The work output is 250 kJ/kg. The changes in kinetic and potential energies are negligible. The heat transfer from the turbine casing to the surroundings is equal to |
| A. | 0 kJ |
| B. | 50 kJ |
| C. | 150 kJ |
| D. | 250 kJ |
| Answer» C. 150 kJ | |
| 175. |
For water at 25 C, dp |
| A. | 2445.25 |
| B. | 2553.25 |
| C. | 2543.25 |
| D. | 2443.25 |
| Answer» E. | |
| 176. |
A rigid container of volume 0.5 m |
| A. | compressed liquid |
| B. | saturated liquid |
| C. | a mixture of saturated liquid and saturated vapor |
| D. | superheated vapor |
| Answer» D. superheated vapor | |
| 177. |
A pure substance at 8 MPa and 400 C is having a specific internal energy of 2864 kJ/kg and a specific volume of 0.03432 m |
| A. | 3239 |
| B. | 3139 |
| C. | 1339 |
| D. | 3339 |
| Answer» C. 1339 | |
| 178. |
Considering the relationship TdS = dU + pdV between the entropy (S), internal energy (U), pressure (p), temperature (T) and volume (V), which of the following statements is correct? |
| A. | It is applicable only for a reversible process |
| B. | For an irreversible process, TdS > dU+ pdV |
| C. | It is valid only for an ideal gas |
| D. | It is equivalent to 1st law, for a reversible process |
| Answer» E. | |
| 179. |
A heat pump absorbs 10 kW of heat from outside environment at 250K while absorbing 15 kW of work. It delivers the heat to a room that must be kept warm at 300 K. The Coefficient of Performance (COP) of the heat pump is____ |
| A. | 1.57 |
| B. | 1.69 |
| C. | 1.67 |
| D. | 0.67 |
| Answer» D. 0.67 | |
| 180. |
The volume and temperature of air (assumed to be an ideal gas) in a closed vessel is 2.87 m3 and 300 K, respectively. The gauge pressure indicated by a manometer fitted to the wall of the vessel is 0.5 bar. If the gas constant of air is R = 287 J/kgK and the atmospheric pressure is 1 bar, the mass of air (in kg) in the vessel is |
| A. | 1.67 |
| B. | 3.33 |
| C. | 5.00 |
| D. | 6.66 |
| Answer» D. 6.66 | |
| 181. |
Two identical metal blocks L and M(specific heat = 0.4 kJ/kg K), each having a mass of 5 kg, are initially at 313 K. A reversible refrigerator extracts heat from block L and rejects heat to block M until the temperature of block L reaches 293 K. The final temperature (in K) of block M is ______ . |
| A. | 451 |
| B. | 333 |
| C. | 323 |
| D. | 222 |
| E. | None of these |
| Answer» C. 323 | |
| 182. |
A certain amount of an ideal gas is initially at a pressure p |
| A. | 0.25 |
| B. | 0.75 |
| C. | 1.0 |
| D. | 1.5 |
| Answer» C. 1.0 | |
| 183. |
The stroke and bore of a four stroke spark ignition engine are 250 mm and 200 mm respectively. The clearance volume is 0.001 m |
| A. | 46.40% |
| B. | |
| C. | 56.10% |
| D. | 58.20% |
| E. | 62.80% |
| Answer» D. 58.20% | |
| 184. |
An engine working on air standard Otto cycle has a cylinder diameter of 10 cm and stroke length of 15 cm. The ratio of specific heats for air is 1.4. If the clearance volume is 196.3 cc and the heat supplied per kg of air per cycle is 1800 kJ/kg, the work output per cycle per kg of air is |
| A. | 879.1 kJ |
| B. | 890.2 kJ |
| C. | 895.3 kJ |
| D. | 973.5 kJ |
| Answer» E. | |
| 185. |
For an engine operating on air standard Otto cycle, the clearance volume is 10% of the swept volume. The specific heat ratio of air is 1.4. The air standard cycle efficiency is- |
| A. | 38.3% |
| B. | 39.8% |
| C. | 60.2% |
| D. | 61.7% |
| Answer» E. | |
| 186. |
An ideal air standard Otto cycle has a compression ratio of 8.5. If the ratio of the specific heats of air ( ) is 1.4, what is the thermal efficiency (in percentage) of the Otto cycle? |
| A. | 575 |
| B. | 45.7 |
| C. | 52.5 |
| D. | 95 |
| Answer» B. 45.7 | |
| 187. |
In a spark ignition engine working on the ideal Otto cycle, the compression ratio is 5.5. The work output per cycle (i.e., area of the P V diagram) is equal to 23.625 10 |
| A. | 4.295 bar |
| B. | 5.250 bar |
| C. | 86.870 bar |
| D. | 106.300 bar |
| Answer» C. 86.870 bar | |
| 188. |
An IC engine has a bore and stroke of 2 units each. The area to calculate heat loss can be taken as |
| A. | 4 |
| B. | 5 |
| C. | 6 |
| D. | 4 |
| Answer» B. 5 | |
| 189. |
Gauge pressure of air to which the ball must have been originally inflated so that it would be equal 1 bar gauge at the stadium is |
| A. | 2.23 bar |
| B. | 1.94 bar |
| C. | 1.07 bar |
| D. | 1.00 bar |
| Answer» D. 1.00 bar | |
| 190. |
An ideal gas undergoes a reversible process in which the pressure varies linearly with volume. The conditions at the start (subscript 1) and at the end (subscript 2) of the process with usual notation are: p |
| A. | 16 kJ |
| B. | 25 kJ |
| C. | 18 kJ |
| D. | 15 kJ |
| Answer» E. | |
| 191. |
A well insulated rigid container of volume 1 m |
| A. | 1195.4 K |
| B. | 1295 K |
| C. | 1295.4 K |
| D. | 2295.4 K |
| Answer» D. 2295.4 K | |
| 192. |
A Carnot engine (CE-1) works between two temperature reservoirs A and B, where T |
| A. | 50 |
| B. | 25 |
| C. | 40 |
| D. | 30 |
| Answer» B. 25 | |
| 193. |
A reversible cycle receives 40 kJ of heat from one heat source at a temperature of 127 C and 37 kJ from another heat source at 97 C. The heat rejected (in kJ) to the heat sink at 47 C is________ |
| A. | 87 |
| B. | 64 |
| C. | 68 |
| D. | 75 |
| Answer» C. 68 | |
| 194. |
The heat removal rate from a refrigerated space and the power input to the compressor are 7.2 kW and 1.8 kW, respectively. The coefficient of performance (COP) of the refrigerator is____. |
| A. | 3 |
| B. | 4 |
| C. | 6 |
| D. | 8 |
| Answer» C. 6 | |
| 195. |
Consider the following two processes; |
| A. | Process I is more irreversible than Process II |
| B. | Process II is more irreversible than Process I |
| C. | Irreversibility associated in both the processes are equal |
| D. | Both the processes are reversible |
| Answer» C. Irreversibility associated in both the processes are equal | |
| 196. |
A source at a temperature of 500 K provides 1000 kJ of heat. The temperature of environment is 27 C. The maximum useful work (in kJ) that can be obtained from the heat source is________. |
| A. | 600 |
| B. | 500 |
| C. | 400 |
| D. | 450 |
| Answer» D. 450 | |
| 197. |
A reversible heat engine receives 2 kJ of heat from a reservoir at 1000 K and a certain amount of heat from a reservoir at 800 K. It rejects 1 kJ of heat to a reservoir at 400 K. The net work output (in kJ) of the cycle is |
| A. | 0.8 |
| B. | 1.0 |
| C. | 1.4 |
| D. | 2.0 |
| Answer» D. 2.0 | |
| 198. |
An irreversible heat engine extracts heat from a high temperature source at a rate of 100 kW and rejects heat to a sink at a rate of 50 kW. The entire work output of the heat engine is used to drive a reversible heat pump operating between a set of independent isothermal heat reservoirs at 17 C and 75 C. The rate (in kW) at which the heat pump delivers heat to its high temperature sink is |
| A. | 50 |
| B. | 250 |
| C. | 300 |
| D. | 360 |
| Answer» D. 360 | |
| 199. |
A heat transformer is device that transfers a part of the heat, supplied to it at an intermediate temperature, to a high temperature reservoir while rejecting the remaining part to a low temperature heat sink. In such a heat transformer, 100 kJ of heat is supplied at 350 K. The maximum amount of heat in kJ that can be transferred to 400 K, when the rest is rejected to a heat sink at 300 K is |
| A. | 12.50 |
| B. | 14.29 |
| C. | 33.33 |
| D. | 57.14 |
| Answer» E. | |
| 200. |
The molar specific heat at constant volume of an ideal gas is equal to 2.5 times the universal gas constant (8.314 J/mol-K). When the temperature increases by 100 K, the change in molar specific enthalpy is______J/mol. |
| A. | 2009.9 |
| B. | 2909.9 |
| C. | 1909.9 |
| D. | 2909 |
| Answer» C. 1909.9 | |