Thermodynamics Questions and Answers

A 50 gm lead bullet specific heat 0 02 cal gm is initially at 30 C It is fired vertically up speed of 840 m sec on returning to the starting level strikes a cake of ice at 0 C How much ice is melted Assume that all energy is spent in melting only Latent heat of ice 80 cal gm Write the REE 1988 5 answer in gms to nearest integer

two process I and II as shown PA b V The heat absorbed and work done in process I are 100 J and 80 J respectively If work done in process II is 60 J then heat absorbed in process Il will be 1 90 J 3 80 J 2 85 J 4 75 J

1 kg of water at 373 K is converted into steam at same temperature Volume of 1 cm of water becomes 1671 cm on boiling What is the change in the internal energy of the system if the latent heat of vaporisation of water is 5 4 x 105 cal kg

1gm of H at S T volume occupie 0 7m of Hg will ti 1 40 1 lit 3 46 6 lit occupies 11 2 litre The y 3gm of H at 300K and 2 46 7 lit 4 47 9 lit

Two cylinders A and B of equal capacity are connected to each other via a stop cock A contains an ideal gas at standard temperature and pressure B is completely evacuated The entire system is thermally insulated The stop cock is suddenly opened The process is 1 isothermal 2 adiabatic 3 isochoric 4 isobaric

Two Carnot engines A and B are operated in series The first one A receives heat at T 600 K and rejects to a reservoir at temperature T The second engine B receives heat rejected by the first engine and in turn rejects to a heat reservoir at T3 400 K Calculate the temperature T if the work outputs of the two engines are equal 2019 Main 9 Jan II

In adiabatic process volume of monoatomic gas increases by 6 then find percentage change in temperature 1 2 3 2 2 4 4 4

51 In an energy recycling process X g of steam at 100 C becomes water at 100 C which converts Y g of ice at 0 C into water at 100 C The ratio of X Y will be 1 A C 3 3 2 B D 2 UGET M A H E Manipal 2005 SOCCRAT 3

A vessel contains 5 mole of O The system is given heat at constant pressure As a result the gas expands and does 120 J of work The heat supplied to gas is 1 310 J 3 420 1 2 390 J 4 560 J

g ice cube is dropped into 45 g of water kept in a glass If the water was initially at a temperature of 28 C and the temperature of ice 15 C find the final temperature in C of water Specific heat of ice 0 5 cal g C and L 80 cal g 1 14 2 7 3 28 4 None

Consider two insulated chambers A B of same volume connected by a closed knob S 1 mole of perfect gas is confined in chamber A What is the change in entropy of gas when knob S is opened R 8 31 J mol K 1 1 1 46 J K 2 3 46 J K 3 5 46 J K 4 7 46 J K S 3 B A

6 A fixed amount of an ideal monoatomic gas is taken through the cycle ABCD as shown in the figure The efficiency of the cycle will be P 3P Po 1 22 2 A B Vo C Di 3V 2 33 33

One kg of a diatomic gas is at a pressure of 8x104 N m The density of the gas is 4 kg m What is the energy of the gas due to its thermal motion AIEEE 2009 a 3x104 J c 6 104 J b 5 104 J d 7 104 J

A Carnot s reversible engine converts of heat input 6 into work When the temperature of the sink is reduced by 62 K the efficiency of Camot s cycle becomes 1 3 The temperature of the source and the sink in kelvin are respectively a 372 310 b 472 410 c 310 372 d 744 682

3 10 8 To decrease the pressure of the gas by 10 at constant temperature then change in volume should be 1 10 decrease 3 11 11 increase 2 10 increase 4 9 1 increase

63 A gas at a temperature 300 K and pressure 30 atm is allowed to expand to atmospheric pressure If the volume becomes 10 times its initial volume the final temperature beocmes 1 100 C 3 373 C 97 E 2 373K 4 100K

A gaseous mixture contains equal number of hydrogen and nitrogen molecules Specific heat measurements on this mixture at temperatures below 100 K would indicate that the value of y ratio of specific heats for this mixture is SCRA 1998 a 3 2 c 5 3 b 4 3 d 7 5 d three moles of diatomic

9 A system is taken from state a to state c by two paths adc and abc as shown in the figure The internal energy at a is U 10 J Along the path adc the amount of heat absorbed 8Q 50 J and the work obtained SW 20 J whereas along the path abc the heat absorbed SQ 36 J The amount of work along the path abc is P d a V C b 2 10 J

49 Curve between the rate of cooling R and body temperature 0 plotted on Y and X axes respectively is Y Y 1 0 3 Y X 2 O 4 Y O 4 k0o X X

How does the pressure of an ideal gas change during the process shown in the diagram V a b T 1 Pressure increases continuously 2 Pressure decreases continuously 3 Pressure first increases and then decreases

5 The average degrees of freedom per molecule for a gas is 6 The gas performs 25J of work when it expands at constant pressure The heat absorbed by gas is 1 75J 2 100J 3 150J 4 125J

200 g of water at 50 C 100 g ice at 20 C and 20 g steam at 100 C are added together in a thermally insulating vessel It is given that LSTEAM 540 cal g specific heat capacity of ice 0 5 cal g C and LICE80 cal g The final temperature of the mixture is x C then find x where denotes greatest integer function us

3 70 A given amount of a gas heated till the volume and pressure are each increased by 1 then temperature increases by 1 0 5 2 1 3 2 4 4

The specific heat capacity of a metal at low temperature 7 is given as T 400 A 100 gram vessel of this metal is to be cooled from 20 K to 4 K by a special refrigerator operating at room temperature 27 C The amount of work required to cool the vessel is AIEEE 2011 1 Less than 0 028 kJ 2 Equal to 0 002 kJ 3 Greater than 0 148 kJ C kJK kg 32 Rotwe 0118 kl and 0 028 kl

Dha h h 1 10 1 16 m or In the Pressure versus Volume graph shown in the process of going from a to b 60 J of heat is added and in the process of going from b to d 20 J of heat is added In the process of going from a to c to d what is the total heat added w 15 A 80 J B 65 J Pressure 8 Pa 3 Pa b 2 m 5 m C 60 J Volume D 56 J

36 The time of reverberation of a room A is one second What will be the time in seconds of reverberation of a room having all the dimensions double of those of room A AIPMT Prelims 2006 1 2 2 4 3 1 2 4 1

Comprehension Q 6 to Q 8 A simple heat engine consists of a movable piston in a cylinder filled with an ideal monoatomic gas Initially the pressure reaches 32P the piston is released allowing the gas to expand so that no heat either enters or the gas in the cylinder is at a pressure Po and volume Vo The gas is slowly heated at constant volume Once escapes the gas as the piston moves Once the pressure has returned to Po the outside of the cylinder is cooled back to the original temperature keeping the pressure constant A Vo Vmax Volume Let Vmax be the maximum volume achieved by the gas during the cycle What is V max B 4V AY8V C 2V0 D 16V In terms of P and V determine the heat removed from the gas during a complete cycle D 2 5 P Vo A 59 93 5 What is the efficiency of this cycle Povo 32P B Pressure 23 3 2 2 Povo B Po 57 93 19 C Povo 58 93 in terms of V D none of these

5 An ideal gas is taken through a process as shown in the figure It absorbs 100 J of energy during the process AB No heat is absorbed or rejected along the process BC and rejectes 140 J during the process CA During the process BC 60 J of work is done on the gas Internal energy of the gas at A is 2000 J The internal energy at C is TS EAMCET 2016 1 1620 J 2 620 J 3 216 J 4 2160 J P C B A C

A 2kW resistance heater wire whose thermal conductivity is K 15 w m k has a diameter of D 4 mm and a length of L 0 5 m and is used to boil water see fig If the outer surface temperature of the resistance wire is Ts 105 C determine the temperature in C at the centre of the wire Assume radial heat flow Consider a following nuclear reaction D 9mm T 105 C

An ideal gas at 27 C is compressed adiabatically to 8 27 of its original volume The rise in temperature is take y 5 3 a 475 C c 275 C b 150 C d 402 C

5 Reversible expansion of an ideal gas under isothermal and adiabatic conditions are as shown in the figure P A PA VA TA B PB VB TB C Pc Vc Tc V AB Isothermal expansion AC Adiabatic expansion Which of the following options is not correct 1 AS isothermal ASadiabatic SE D 2 TA TB 3 Wisothermal Wadiabatic es

Let P V and T denote respec volume and temperature of an ideal gas The correct graph for adiabatic process is 1 3 TAV dP V TOP dP TOV 28 5 dP dv V K V

In an adiabatic process if pressure P and density d of a monatomic gas are related as P is proportional to dx then x is equal to 1 3 275 57 2 4 3 55 3

18 The pressure P versus volume V of an ideal gas varies as shown in the given figure Which of the following graph may represent the variation of pressure P with temperature 7 P 1 3 P T 2 4 V P T

done by gas is P 200 kPa 100 kPa 1 5 kJ 3 5 kJ D 100 cc C iB 200 cc V 2 2 5 kJ 4 7 5 kJ

8 A closed system undergoes a change of state by process 1 2 for which Q12 10J and W12 5 J The system is now returned to its initial state by a different path 2 1 for which Q1 is 3 J The work done by the gas in the process 2 lis a 8 J c 2 J b zero d 5 J

Find the ratio of the lengths of an iron rod and an aluminium rod for which the difference in the lengths is independent of temperature Coefficients of linear expansion of iron and aluminium are 12x 10 6 C and 24 x 10 6 C respectively

An ideal refrigerator has a freezer at temperature 12 C The coefficient of performance temperature of the engine is 5 The of the air to which the heat ejected is a 50 C 40 2 C b 45 2 C d 37 5 C

A spherical soap bubble surface tension S encloses n moles of mono atomic gas The gas is heated slowly so that the effective surface area of the bubble increases by 3nR 25 A B C per unit increment in temperature of the gas the specific heat for this process is assume surrounding is vacuum 3R 1 32 2 2 Check all that apply 2 5R 2 3 7R 2 4 3R

When one mole of monoatomic gas expands at constant pressure the ratio of the heat supplied that increases the internal energy of the gas and that is used in expansion is c 9 10 a b zero a 2 3

During an adiabatic process the pressure of a gas is found to be proportional to the cube of its temperature a 2 c 3 2 Cp The ratio of for the gas is C b d 5 3 2013

Figure shown below is a graph of a monoatomic gas which undergoes a cyclic process If work done by gas in process BC is x the heat absorbed in process CA is PA 2Pof A 3 Pot 1 x ln2 X CI To 4 B 2T T 2 x In2 X

Two moles of Helium gas undergoes a cyclic process as shown in figure Assume gas to be ideal The net change in heat energy is P atm 2 L 1 1000 J 3 1153 J 300 400 T K 2 1050 J 4 1100 J

0 100 mol of an ideal gas is heated from 10 to 20 C keeping its a volume constant b pressure constant Let AU and AU denote the change in the internal energy of the gas due to process a and b respectively Then which of the following shall be true a AU AU ime c AU AUb b AU AU AU AU 0 d a teta

29 What is the volume occupied by one mole of an ideal gas at STP a 10 4 L c 22 4 L b d 11 4 L 33 4 L

3 A gas is taken along the path AB as shown in figur 26 E8 If 70 cal of heat is extracted from the gas in the 250 cc 100 cc A 200 kPa Figure 26 E8 B 500 kPa

An experiment is being performed by a student in laboratory on ideal gas He found the value of Cp Cy equal to 1 00 R for a gas sample in state A Now he performed the experiment on the same gas and found Cp Cy as 1 03 R in state B Let PA PB denote the pressures and TA TE denote the temperatures of states A and E respectively Which of the following will be correct 1 PA PB and TA TB 2 PA PB and TA TB 3 PA PB and TA TB

1 r 3 5 2 r 4 r4 A sample of 0 1 g of water at 100 C and normal pressure 1 013 x 105 Nm 2 requires 54 cal of heat energy to convert to steam at 100 C If the volume of the steam produced is 167 1 cc the change in internal energy of the sample is 1 104 3 J A 2 208 7 J 3 42 2 J 4 84 5 J 8

56 Two different masses of a gas separately in vessels of equal volume The T p curve for mass 2m makes angle a with T axis and that for mass m takes angle with T axis then a tan a tan B c tan 2 tan a b tan a 2 tan B d None of these

Carnot Theorem No heat engine operating between two given temperatures can be more efficient than a Carnot engine operating between the same two temperatures