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MCQOPTIONS
This section includes 156 Mcqs, each offering curated multiple-choice questions to sharpen your Thermodynamics knowledge and support exam preparation. Choose a topic below to get started.
| 101. |
A heat engine is supplied with 1200 kW of heat at a constant temperature of 600 K and it rejects 700 kW of heat at 300 K. Which of the following is true for this heat engine? |
| A. | It is a reversible cycle |
| B. | It is an irreversible cycle |
| C. | It is an impossible cycle |
| D. | The efficiency of this cycle is greater than 50% |
| Answer» C. It is an impossible cycle | |
| 102. |
2500 kJ/min heat is supplied to a heat engine at 727°C. It rejects heat at 900 kJ/min at 223°C. This type of engine is ________. |
| A. | ideal |
| B. | irreversible |
| C. | impossible |
| D. | practical |
| Answer» D. practical | |
| 103. |
Maximum efficiency of the heat engine is produced by ________ cycle: |
| A. | Diesel |
| B. | Otto |
| C. | Carnot |
| D. | Dual |
| Answer» D. Dual | |
| 104. |
A reversible heat engine receives 240 kJ/s heat from a source at 627°C and rejects heat to a sink at 300 K. The available power is: |
| A. | 100 kW |
| B. | 160 kW |
| C. | 80 kJ/s |
| D. | 20,000 J/s |
| Answer» C. 80 kJ/s | |
| 105. |
A machine which is transferring heat from the lower body to the higher body without consuming any external work. Such machine is an example of: |
| A. | perpetual Motion Machine of the fourth kind |
| B. | Perpetual Motion Machine of the second kind |
| C. | Perpetual Motion Machine of the third kind |
| D. | Perpetual Motion Machine of the first kind |
| Answer» C. Perpetual Motion Machine of the third kind | |
| 106. |
According to Kelvin – Planck statement, a perpetual motion machine |
| A. | Of first kind is possible |
| B. | Of first kind is impossible |
| C. | Of second kind is impossible |
| D. | Of seconds kind is possible |
| Answer» D. Of seconds kind is possible | |
| 107. |
If the temperature of the hot reservoir is increased, the efficiency of the Carnot engine: |
| A. | does not change |
| B. | decreases |
| C. | increases |
| D. | will be equal to the efficiency of the practical engine |
| Answer» D. will be equal to the efficiency of the practical engine | |
| 108. |
A Carnot heat pump works between temperature limits of 277°C and 27°C. Its COP is |
| A. | 1.108 |
| B. | 1.2 |
| C. | 2.2 |
| D. | 9.26 |
| Answer» D. 9.26 | |
| 109. |
Increase in entropy of a system represents |
| A. | Increase in availability of energy |
| B. | Increase in temperature |
| C. | Decrease in pressure |
| D. | Degradation of energy |
| Answer» E. | |
| 110. |
A tank containing air is stirred by a paddle wheel. The work input to the paddle wheel is 8000 kJ and the heat transferred to the surroundings from the tank is 5000 kJ. The external work done by the system is |
| A. | 3000 kJ |
| B. | 8000 kJ |
| C. | 5000 kJ |
| D. | Zero |
| Answer» E. | |
| 111. |
A Carnot cycle refrigerator operates between 250 K and 300 K. Its coefficient of performance is |
| A. | 6 |
| B. | 5 |
| C. | 1.2 |
| D. | 0.8 |
| Answer» C. 1.2 | |
| 112. |
A more effective way of increasing efficiency of Carnot engine where TH is source and TL is the sink is: |
| A. | Increase TH, keeping TL as constant |
| B. | Decrease TL, keeping TH constant |
| C. | Increasing efficiency is impossible |
| D. | None of the above |
| Answer» C. Increasing efficiency is impossible | |
| 113. |
Consider the following two processes:a. A heat source at 1200K loses 2500kJ of heat to sink at 800Kb. A heat source at 800K loses 2000kJ of heat to sink at 500KWhich of the following statements is TRUE? |
| 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 is equal |
| D. | Both the processes are reversible |
| Answer» C. Irreversibility associated in both the processes is equal | |
| 114. |
As shown in figure below, an ideal gas is confined to a cylinder by a piston. The piston is pushed down slowly so that the gas temperature remains at 27°C. During the compression, 900 J of work is done on the gas. Find the entropy change of the gas. |
| A. | 3 J/K |
| B. | -3 J/K |
| C. | -6 J/K |
| D. | 6 J/K |
| Answer» C. -6 J/K | |
| 115. |
A cyclic device operates between three thermal reservoirs, as shown in the figure. Heat is transferred to/form the cyclic device. It is assumed that heat transfer between each thermal reservoir and the cyclic device takes place across negligible temperature difference. Interactions between the cyclic device and the respective thermal reservoirs that are shown in the figure are all in the form of heat transfer.The cyclic device can be |
| A. | A reversible heat engine |
| B. | A reversible heat pump or a reversible refrigerator |
| C. | An irreversible heat engine |
| D. | An irreversible heat pump or an irreversible refrigerator |
| Answer» B. A reversible heat pump or a reversible refrigerator | |
| 116. |
A reversible engine operates between temperatures T1 and T2. The energy rejected by this engine is received by a second reversible engine at temperature T2 and rejected to a reservoir at temperature T3. If the efficiencies of the engines are same then the relationship between T1, T2 and T3 is given by |
| A. | \({T_2} = \frac{{\left( {{T_1} + {T_3}} \right)}}{2}\) |
| B. | \({T_2} = \sqrt {T_1^2 + T_3^2} \) |
| C. | \({T_2} = \sqrt {{T_1}{T_3}} \) |
| D. | \({T_2} = \left( {{T_1} + 2{T_3}} \right)\) |
| Answer» D. \({T_2} = \left( {{T_1} + 2{T_3}} \right)\) | |
| 117. |
In a Carnot cycle, heat is transferred at ________. |
| A. | Constant pressure |
| B. | Constant volume |
| C. | Constant temperature |
| D. | Constant enthalpy |
| Answer» D. Constant enthalpy | |
| 118. |
A researcher claims that he has developed an engine, which while working between source and sink temperatures of 377°C and 27° C rejects only 50 % of absorbed heat. What will his engine be? |
| A. | An impossible engine |
| B. | A Stirling engine |
| C. | A reversible engine |
| D. | A practical engine |
| Answer» E. | |
| 119. |
A heat engine performs a work of 100 kJ per cycle. The efficiency of the engine is 50%. What will be the amount of heat rejected (in kJ) per cycle? |
| A. | 0 |
| B. | 50 |
| C. | 100 |
| D. | 200 |
| Answer» D. 200 | |
| 120. |
A Carnot engine rejects 30% of absorbed heat to a sink at 30°C. The temperature of the heat source is |
| A. | 100°C |
| B. | 433°C |
| C. | 737°C |
| D. | 1010°C |
| Answer» D. 1010°C | |
| 121. |
In statistical thermodynamics, entropy is defined as |
| A. | Reversible heat transfer |
| B. | Measure of reversibility of a system |
| C. | Degree of randomness |
| D. | A universal property |
| Answer» D. A universal property | |
| 122. |
One kilogram of water at room temperature is brought into contact with a high-temperature thermal reservoir. The entropy change of the universe is |
| A. | equal to entropy change of the reservoir |
| B. | equal to entropy change of water |
| C. | equal to zero |
| D. | always positive |
| Answer» E. | |
| 123. |
One reversible heat engine operates between 1600 K and T2 K and another reversible heat engine operates between T2 K and 400 K. If both the engines have the same thermal efficiency, the temperature T2 is, |
| A. | 800 K |
| B. | 1000 K |
| C. | 1200 K |
| D. | 1400 K |
| Answer» B. 1000 K | |
| 124. |
During January, at a location in Rohtang, winds at -6°C can be observed. Several meters below the ground, the temperature remains at 27°C. A scientist claims to have device a power cycle exploiting this situation that has a thermal efficiency of 10%. Whether the claim is true? |
| A. | True |
| B. | False |
| C. | Can’t say |
| D. | Insufficient data |
| Answer» B. False | |
| 125. |
A 30-ohm resistor carrying a constant current of 1 Ampere is kept at a constant temperature of 27°C by a stream of cooling water. What will be the rate of change in entropy of the universe? |
| A. | 10 W/K |
| B. | 0.1 W/K |
| C. | 0.1 J/K |
| D. | 10 J/K |
| Answer» C. 0.1 J/K | |
| 126. |
If the pressure at station Q is 50 kPa, the change in entropy (SQ - SP) in kJ/kgK is |
| A. | - 0.155 |
| B. | 0 |
| C. | 0.160 |
| D. | 0.355 |
| Answer» D. 0.355 | |
| 127. |
An actual engine is to be designed having same efficiency as the Carnot cycle. Such a proposition is ________. |
| A. | Feasible |
| B. | Impossible |
| C. | Possible |
| D. | Desirable |
| Answer» C. Possible | |
| 128. |
A Carnot cycle operates between temperatures of 727°C and 227°C, the efficiency of the engine is: |
| A. | 40% |
| B. | 50% |
| C. | 60% |
| D. | 45% |
| Answer» C. 60% | |
| 129. |
For condition for reversibility of a cycle is |
| A. | \(Cyclic\smallint \frac{{dQ}}{T} < 0\) |
| B. | \(Cyclic\smallint \frac{{dQ}}{T} > 0\) |
| C. | \(Cyclic\smallint \frac{{dQ}}{T} = 0\) |
| D. | None of these |
| Answer» D. None of these | |
| 130. |
Perpetual motion machine of second kind (PMM-II) violates the |
| A. | Zeroth law of thermodynamics |
| B. | First law of thermodynamics |
| C. | Second law of thermodynamics |
| D. | Third law of thermodynamics |
| Answer» D. Third law of thermodynamics | |
| 131. |
A perfect gas having P1 = 0.1 N/mm2, V1 = 0.18 m3, T1 = 20°C is compressed to \(\frac{1}{10}\) of its volume in an isothermal process. The change in entropy is |
| A. | – 141.45 J/K |
| B. | 141.45 J/K |
| C. | – 4144.23 J/K |
| D. | Zero |
| Answer» B. 141.45 J/K | |
| 132. |
For reversible adiabatic process, change in entropy is |
| A. | Maximum |
| B. | Minimum |
| C. | Zero |
| D. | Unpredictable |
| Answer» D. Unpredictable | |
| 133. |
Entropy change depends on ________. |
| A. | Mass transfer |
| B. | Change of temperature |
| C. | Thermodynamic state |
| D. | Heat transfer |
| Answer» B. Change of temperature | |
| 134. |
A mass of 5 kg of water at 293 K is turned completely to ice at 273 K. The entropy change in the process is |
| A. | 6.13479 kJ/K |
| B. | – 1.4847 kJ/K |
| C. | – 7.6195 kJ/K |
| D. | 8.3195 kJ/K |
| Answer» D. 8.3195 kJ/K | |
| 135. |
In Clausius theorem the reversible path is substituted by ________. |
| A. | reversible isobars |
| B. | reversible isotherms |
| C. | reversible isochoric |
| D. | None of these |
| Answer» C. reversible isochoric | |
| 136. |
300 kJ of heat is supplied at constant temperature of 500 K, to a heat engine. The heat rejection takes place at 300 K. The following result are obtained (a) 210 kJ (b) 180 kJ (c) 150 kJ. Identify whether result is a reversible cycle. Irreversible cycle or impossible cycle respectively |
| A. | reversible / irreversible / impossible respectively |
| B. | irreversible / reversible / impossible respectively |
| C. | irreversible / impossible / reversible respectively. |
| D. | None of the above |
| Answer» C. irreversible / impossible / reversible respectively. | |
| 137. |
Kelvin-Planck's law deals with conservation of which of the following? |
| A. | Work |
| B. | Heat |
| C. | Mass |
| D. | Heat into work |
| Answer» E. | |
| 138. |
For an ideal gas with constant properties undergoing a quasi-static process, which one of the following represents the change of entropy (Δs) from state 1 to 2? |
| A. | \({\rm{\Delta }}s = {C_P}\ln \left( {\frac{{{T_2}}}{{{T_1}}}} \right) - R\ln \left( {\frac{{{P_2}}}{{{P_1}}}} \right)\) |
| B. | \({\rm{\Delta }}s = {C_V}\ln \left( {\frac{{{T_2}}}{{{T_1}}}} \right) - {C_p}\ln \left( {\frac{{{V_2}}}{{{V_1}}}} \right)\) |
| C. | \({\rm{\Delta }}s = {C_P}\ln \left( {\frac{{{T_2}}}{{{T_1}}}} \right) - {C_V}\ln \left( {\frac{{{P_2}}}{{{P_1}}}} \right)\) |
| D. | \({\rm{\Delta }}s = {C_V}\ln \left( {\frac{{{T_2}}}{{{T_1}}}} \right) + R\ln \left( {\frac{{{V_1}}}{{{V_2}}}} \right)\) |
| Answer» B. \({\rm{\Delta }}s = {C_V}\ln \left( {\frac{{{T_2}}}{{{T_1}}}} \right) - {C_p}\ln \left( {\frac{{{V_2}}}{{{V_1}}}} \right)\) | |
| 139. |
Carnot cycle consists of |
| A. | Two constant volume and two isentropic processes |
| B. | Two isothermal and two isentropic processes |
| C. | Two constant pressure and two isentropic processes |
| D. | One constant volume, one constant pressure and two isentropic processes |
| Answer» C. Two constant pressure and two isentropic processes | |
| 140. |
A reversible engine works between temperature limits of 260°C and 60° C. To improve the performance, we have to |
| A. | Raise the source temperature to 300°C |
| B. | Lower the sink temperature to 30°c |
| C. | Insulate the engine |
| D. | None of the above |
| Answer» C. Insulate the engine | |
| 141. |
A refrigerating machine working on a reversed Carnot cycle takes 2 kW of heat from the system while working between temperatures of 300 K and 200 K. COP and power consumed by the cycle will be |
| A. | 1, 1 kW |
| B. | 1, 2 kW |
| C. | 2, 1 kW |
| D. | 2, 2 kW |
| Answer» D. 2, 2 kW | |
| 142. |
Change of entropy depends upon ________. |
| A. | Change of mass |
| B. | Change of temperature |
| C. | Change of specific heats |
| D. | Change of heat |
| Answer» E. | |
| 143. |
A heat engine receives 1 kW of heat transfer at 1200 K and gives out 600 W as work, with the rest as heat transfer to the ambient at 300 K. The second-law efficiency of the engine is: |
| A. | 70% |
| B. | 90% |
| C. | 80% |
| D. | 60% |
| Answer» D. 60% | |
| 144. |
If a heat engine attains 100% thermal efficiency, it violates |
| A. | Zeroth law of thermodynamics |
| B. | First law of thermodynamics |
| C. | Second law of thermodynamics |
| D. | Third law of thermodynamics |
| Answer» D. Third law of thermodynamics | |
| 145. |
If a heat engine gives an output of 3 kW when the input is 10000 J/sec then the thermal efficiency of the engine will be |
| A. | 20% |
| B. | 30% |
| C. | 70% |
| D. | 76.7% |
| Answer» C. 70% | |
| 146. |
Air is compressed to half the volume at constant pressure, then the entropy |
| A. | Increase |
| B. | Decrease |
| C. | Does not change |
| D. | Not predictable |
| Answer» C. Does not change | |
| 147. |
Entropy is a measure of ________. |
| A. | Reversible heat transfer |
| B. | System efficiency |
| C. | Degree of randomness |
| D. | System temperature |
| Answer» D. System temperature | |
| 148. |
A Carnot engine operates between 37°C and 347°C. If the engine produces 620 kJ of work, the entropy change during heat addition is |
| A. | 1 kJ/K |
| B. | 2 kJ/K |
| C. | 3 kJ/K |
| D. | 4 kJ/K |
| Answer» C. 3 kJ/K | |
| 149. |
A Carnot engine operates between 300 K and 600 K. If the entropy change during heat addition is 1 kJ/K, the work produced by the engine is: |
| A. | 100 kJ |
| B. | 200 kJ |
| C. | 300 kJ |
| D. | 400 kJ |
| Answer» D. 400 kJ | |
| 150. |
Clausius’ statement and Kelvin - Planck’s statement are ________. |
| A. | not connected |
| B. | two parallel statements of the second law |
| C. | violation of one does not violates the other |
| D. | false statements |
| Answer» C. violation of one does not violates the other | |