Thermodynamics Questions and Answers

sider the following figure The x axis is marked in increments of 1 m tical axis is P Pa Point is located at 1 6 105 and point is located at 4 00 2 x 106 The graph starts at pointi goes P Pa and th to the right with constant pressure of 6 x 106 Pa while reaching a 6 X 106 volume of 2 00 4 X 106 The paph then goes down and to the right to the pressure is 2 x 10 Pa and the volume is then goes to the rifht to end at point f The en the graph and the horizontal axis and between 3 00 m The gra 2 106 V 1 m and V 4 003 is shaded An arrow along the graph V m points in the direction of increasing volume a Determine the work done on a gas that expands from i to f as indicated in the figure MJ b How much work is performed on the gas if it is compressed from f to i along the same p

A Carnot engine has an efficiency of 20 when the temperature of the sink is 120 F Then the efficiency is increased to 80 by changing the source temperature only What is the change in temperature of the source

Three particles have to be accommodated in four available states Calculate the number of ways in whic this can be done if the particles obey a Classical statistics b B E statistics and c F D statistics

A litre of dry air at STP expands adiabatically to a volume of 3 litres If y 1 40 the work done by air is 314 4 6555 Take air to be an ideal gas 1 90 5 J 3 60 7 J 2 48 J 4 100 8 J

19 Which of the following methods will enable the volume of ideal gas to be increased four times 1 Double the temperature and reduce the pressure to half 2 Double the temperature and also double the pressure 3 Reduce the temperature to half and double the pressure 4 Reduce the temperature to half and reduce the pressure to half

A carnot engine em change in temperature cy 40 and ten of source An ideal refrigerator is working between temperature 27 C and 127 C If it expells 120 calo one second then calculate its wattage

A balloon filled with of 1 0 g of hydrogen is in thermal equilibrium air in a room Root mean square speed of air molecules at the temperature is 500 m s the average molecular mass of air molecule 29 g mol If hydrogen in the balloon is considered an ideal gas its t internal energy is closest to a 1813 J c 4223 J 3021 J d 6042 J

9 A piston can slide which contains an ideal mono atomic gas The piston and surface of the cylinder are coated with a thin layer of a pe insulating material Initially the piston in equilibrium d cylinder into two parts A and B which are not necessarily temperatures of the gases in both the parts are equal Now is held in its initial position and the gas in part A is sup amount of heat then the piston is released What will the p its subsequent motion It will execute oscillatory motion of definite amplitude It will stop somewhere to the right of its initial position after several oscillations of decreasing amplitude It will stop exactly where it had started after several oscillations of decreasing amplitude Certainly it will execute oscillations of decreasing amplitude but the position where it will finally stop depends on the amount of heat supplied

3 An ideal gas with adiabatic exponent y goes a cyclic process as shown in figure Within Te which the absolute temperature varies with n 4 Fold 4 The percentage efficiency of this cycle is A 20 3 B P 25 4 B C 25 D none of these

CTQ 28 P V plots for two gases during adiabatic process are shown in the figure Plots 1 and 2 should correspond respectively to a He and O c He and Ar Party no Dia b 02 and He d O and N O diatomicgas 91 1 mono 2 0 702

A reversible refrigerator operates between a low temperature reservoir at 7 and a high temperature reservoir at 71 Its coefficient of performance is given by TH TLYTH ON 00 TH TH TL OD TH TH TL DE TL TH TL TH TTL

10 Mathematic 30 English 5 Q4 The average energy of the He atom on the surface of the sun which is at a temperature of 6000 K is Given that kg 1 3 0 4 6 21x102 0 8 8 28x10 20 C 124x10j 0 621x10 J

A cylindrical vessel is divided in two parts by a fixed partition which is perfectly heat conducting The wall and piston are thermally insulated from surroundings The left side contains 0 5 moles of gas with C 2R at temperature of 300K The right side contains 4 moles of mixture of gas with C 1 75R at same temperature of 300K The piston compresses slowly the right side from volume of V to Find the total change in internal energy of gases If AU nx 10J fill n in OMR sheet take R S L unit 25 3 A 10 B 2x10 J I C 4 10 J D Cannot be Calculated

4 16 An imaginary engine receives heat and does work on a slowly moving piston at such rates that the cycle of operation of 1 kg of working fluid can be represented as a circle 10 cm in diameter on a p v diagram on which 1 cm 300 kPa and 1 cm 0 1 m kg a How much work is done by each kg of working fluid for each cycle of operation b The thermal efficiency of an engine is defined as the ratio of work done and heat input in a cycle If the heat rejected by the engine in a cycle is 1000 kJ per kg of working fluid what would be its thermal efficiency L0421 Ans a 2356 19 kJ kg b 0 702

3 The average translational energy and the r m s speed of molecules in a sample of oxygen gas at 300 K are 6 21 10 1 J and 484 ms respectively The corresponding values at 600 K are nearly assuming ideal gas behaviour a 12 42 10 21 J 968 ms 1 b 8 78 10 21 J 684 ms 1 c 6 21 10 21 J 968 ms 1 d 12 42 10 21 J 684 ms 1 IT 97

3 On what factors does the efficiency of Carnot engine depend 4 What are two essential features of Carnot s ideal heat engine 5 Plot a graph between internal energy U and Temperature T of an ideal ga

12 V t graph is obtained as shown in the figure The work done by the force is represented by the graph 1 PQ 2 QR V P 3 RS S T t 4 ST

One mole of an ideal monoatomic gas requires 210 J heat to raise the temperature by 10K when heated at constant pressure If the same gas is heated at constant volume to raise the temperature by 10 K then heat required is Question Type Single Correct Type 1 238 J 2 126 J 3 210 J

Three samples of the same gas A B and C y 3 2 have initially equal volume Now the volume of each sample is doubled The process is adiabatic for A isobaric for B and isothermal for C If the final pressures are equal for all the three samples the ratio of their initial pressures is Question Type Single Correct Type 1 2 2 2 1 2 2 2 1 2 3 2 1 2

15 Entropy of a system decreases 1 When heat is supplied to a system at constant temperature 2 When heat is taken out from the system at constant temperature 3 At equilibrium 4 In any spontaneous process

Figure shows a cylinder of cross sectional area A and total length 4L containing n moles of oxygen each at temperature T and T K are separated by a fixed piston of length 2L and thermal conductivity K Find the rate of heat flow through the piston after time 2KA t T T Given 5nRL a KA 21 1 1 e b 2L KA T T e 2L t KA 3L KA 7 7 e T T HI 1

View in English A certain quantity of O y 7 5 is compressed isothermally until its pressure is doubled P the gas is then allowed to expand adiabatically until its origional volume is restored the final pressure P3 is term s of initial pressure P is 2 1 5 1148 1 4 Correct Answer 2 P 0 55 P P3 0 76 P1 P3 0 68 P1 P3 255 P

n an total If a gas absorbs 200 J of heat and expands by 500 cm3 against constant pressure of 2 x 105 Nm then change in internal energy is 1 200 J 2 100J 3 100J 4 300J

Which of the following statements is correct 1 Two isothermal curves may intersect 2 Two adiabatic curves may intersect 3 Two different states of gas can be connected by an isothermal process as well as an adiabatic process on a P V diagram 4 An isothermal curve may intersect an adiabatic QUA

The pressure and volume of an ideal gas are related as pa for process A B as shown is figure The pressure and volume at A are 3p and respectively and pressure at B is po The work done in the process A B is found to be x x Povo find value of x Pressure A Volume B

the cell Pb For s Pb 1M Ag 1M Ag s if concentraton of an ion in the anode compartment is increased by a factor of 10 the emf of the cell will a increase by 10 V p b increase by 0 0296 V c decrease by 10 V d decrease by 0 0296 V

c 250 K d 250 C 49 p V diagram of an ideal gas is as shown in figure Work done by the gas in the process ABCD is P a 4povo c 3 povo 2po Po B Vo A D 2V 3V V b 2poVo d povo

15 15 In a mechanical refrigerator the low temperature coils are at a temperature of 23 C and the compressed gas in the condenser has a temperature of 27 C The theoretical coefficient of performance is 5 8 6 6 5

c 40 kg d 50 kg 67 A gas at the temperature 250 K is contained in a closed vessel If the gas is heated through 1K then the percentage increase in its pressure will be a 0 4 c 0 1 b 0 2 d 0 8

1 The following sets of values for Cy and Cp of a gas have been reported by different students The units are cal mole 1 K Which of these sets is most reliable ya C 3 Cp 5 6 C 4 Co 6 c C 3 Cp 2q olisie d Cy 3 Cp 4 2

70 calories of heat are required to raise the temperature of 2 moles of an ideal gas at constant pressure from 30 C to 35 C The amount of heat in cal required to raise the temperature of the same sample of the gas through the same range at constant volume is

A gas expands from i to along the three paths indicated The work done along the three paths denoted by W W and W have the relationship 123456 W a W W b W W W W W W d W W W c

a 0 495 kg c 0 695 kg 25 A cyclic process is shown in the figure Work done during the cyclic process ABCDA is 2x10 4 1 x 102 b 0 595 kg d 0 795 kg P Nm 2 V m b 150J d 900 J B a 1600J c 600 One mole of an ideal monatomic gas at temperature c 31 A u 5 ks spee wire a c 32 The radiu What tensic a

A sphere and a cube of same material and same total surface area are placed in the same evacuated space turn by turn after heating to the same temperature Find the ratio of their initial rates of cooling in the evacuated space 3 1

A gas expands in a frictionless piston cylinder arrangement The expansion process is very slow and is resisted by an ambient pressure of 100 kPa During the expansion process the pressure of the system gas remains constant at 300 kPa The change in volume of the gas is 0 01 m The maximum amount of work that could be utilized from the above process is

Difficulty Level Easy Question N moles of monoatomic gas having translational KE 2U per molecule are mixed adiabatically inside a rigid boundry container with N moles of diatomic gas having translational KE U per molecule What is final temperature of mixture A 3NAU SR 11NAU B 12R 3NAU C 12R D None

Which of the following relationships is valid only for reversible processes undergone by a closed system of simple compressible substance neglect changes in kinetic and potential energy 1 SQ dU SW 2 T ds dU p dV 3 T ds dU SW 4 SQ dU p dV

An ideal diatomic gas undergoes a process AB for which PV indicator diagram is shown Temperature at state A is To When process changes from endothermic to exothermic temperature of the gas is 175 864 To Find the value of a P 3Po Po V B 2V V

3P P P B A C 3V V Al mole of ideal gas initially at Pi 1 Pa Vi 5 m and Ti 0 C is taken through a cycle a shown in above Figure a Find the temperature of gas at point C 2P b Find the net work done on the gas per cycle 4P c What is the net energy added by heat to the gas per cycle 4P

he se K nt ge es 65 Figure shows the isotherms of a fixed mass of an ideal gas at three temperatures TA TB and Tc then A 1 TA TB Tc 2 TA TB TC 3 TB TA TC 4 T TB Tc B C P 7 NODE02 BOBO BA PHYSICS AT A GLANCE CROP ENG 11 THERMAL PHYSICS P65

A non conducting piston of mass m and are So divides a non conducting closed cylinder as shown in the figure A piston having mass m is connected with the top wall of the cylinder by a spring of force constant k The top part is evacuated and the bottom part contains an ideal gas at a pressure Po in the equilibrium position Adiabatic exponent y and in equilibrium length of each part is 1 neglect friction Find the angular frequency for small oscillation Po lllllll m So

An ideal gas expands according to the law PZV constant The internal energy of the gas 1 Increases continuously 2 Decreases continuously 3 Remains constant 4 First increases and then decreases

Patm 76 cm of Hg Given Fatm Air 12 cm Air fig 1 Hg 45 fig 4 8 cm OL Hg Air fig 2 Air Hg When the tube is held at an angle of 45 to the plane with the open end up what should be the length of air a 12 cm b 11 17 cm C 11 0 cm d 10 8 cm

Q 8 Between two isotherms at temperatures 27 and T a process ABCD is performed with an idea monatomic gas AB and CD are adiabatic expansion processes and BC is isobaric expansion process The average molar specific heat capacity of the overall process will be Answer A B Your Attempt 3R 2 5R 2 C 3R 2 D 5R 2 Correct answer Rate this que

CO mic gas undergoes a cyclic process abc as shown on temperature volume T V diagram as shown Hence TA not an isobaric Process fust a graph alo do like 11 V ol otherwis as line would have passed the origin Pressure during ab decreases Y 2 Pressure during ab increases 3 Temperature increases during bc X A Temperature decreases during ca

174 1 4 44 42 6 The average degree of freedom per molecule for a gas is 6 The gas performs 25 of work when it expands at constant pressure The heat absorbed by the gas is a 751 c 1501 b 1001 d 125 50 angle same h energie a I c In A car is observe with an

The P V diagram of a gas undergoing a cyclic process ABCDA is shown in the graph where P is in N m2 and V in cm Identify the incorrect statement P Nm2 a b c 2 10 d 1 10 20 V cm 0 4 of work is done by the gas from A to B 0 2 of work is done on the gas from C to D No work is done by the gas from B to C Work is done by the gas from B to C and on the gas from D to A 42 Three stars A B Chave surface

c 600J d 900J 6 One mole of an ideal monatomic gas at To expands slowly according to the law temperature constant constant If the final temperature is 2To heat supplied to the gas is a 2RT b RT A simple pendulum has time period T The point of a 4 c 3 33 Figure moving space at YM 0 The pos

A mono atomic ideal gas y 1 67 molecular weight 40 is compressed adiabatically from 0 1 MPa 300 K to 0 2 MPa The universal gas constant is 8 314 kJmol K 1 The work of compression of the gas in kJ kg is 1 29 7 2 19 9 3 13 3

An insulator container contains 4 moles of an ideal diatomic gas at temperature T Heat Q is supplied to this gas due to which 2 moles of the gas are dissociated into atoms but temperature of the gas remains constant Then 1 Q 2 RT 2 Q RT 3 Q 3 RT 4 DT