# Thermodynamics worksheet

Thermodynamics is the branch of physics which deals with the relation of heat  with work and energy.Here under are the list of the objectives question related with this topic.The answers are at the bottom.

1>The thermal state of a body is defined by

(1) Heat

(2) Temperature

(3) Cold

(4) Specific heat

2>The heat energy required to raise the temperature of 1 kg of substance through 1°C is called

(1) Heat

(2) Specific heat

(3) Latent heat

(4) Temperature

3>The specific heat of a solid

(1) Is a constant independent of temperature

(2) Varies linearly with temperature

(3) First increases with temperature and then attains a constant value

(4) First decreases with temperature and then attains a constant value

4.>The specific heat of a gas has

(1) Only one unique value

(2) Only two values CP and CV

(3) Any value lying between 0 and infinity depending on the process.

(4) Is always zero

5>The branch of physics which deals with relation between heat and mechanical energy is called

(1) Heat

(2) Thermodynamics

(3) Thermoelectricity

(4) Calorimetry

6>In an isothermal process

(1) Pressure remains constant

(2) Thermal energy remains constant

(3) Volume remains constant

(4) Temperature remains constant

7>In an adiabatic process

(1) Pressure remains constant

(2) Volume remains constant

(3) Thermal energy remains constant

(4) Temperature remains constant

8>The thermodynamic process in which no exchange of heat between system and surroundings takes place is called

(1) Isothermal

(3) Isobaric

(4) Isochoric

9>The thermodynamic process in which pressure of system remains constant is called

(1) Isothermal

(3) Isobaric

(4) Isochoric

10>The boiling water at constant temperature is

(1) Isothermal process

(3) Isochoric process

(4) Isoentropic process

11>The ideal gas equation PV = RT is true for

(1) Isothermal process only

(2) Adiabatic process only

(3) Both isothermal and adiabatic process only

(4) All processes

12> $PV^{\gamma}$ =constant is true for

(1) Isothermal process only

(2) Adiabatic process only

(3) Both isothermal and adiabatic processes only

(4) All processes

13>The specific heats CP and CV bear the relation

(1)  $C_P - C_V = R$

(2) $\dfrac{C_P} { C_V} = R$

(3) $C_P + C_V = R$

(4) $C_V - C_P = R$

14>For hydrogen  $C_P - C_V = a$ and for oxygen gas $C_P - C_V = b$ then the relation between a and b is given by

(1) a =16b

(2) 16b =a

(3) a – 4b

(4) a = b

15>The difference between CP and Cv is

(1) R

(2) 2R

(3) $\dfrac{R}{2}$

(4) Depends on the atomicity of the gas

16>If CP and Cv are in Kilocal/mole K and R in Joule/mole K, then, which of the following relation is true

(1) $C_P - C_V = R$

(2) $C_P - C_V = \dfrac{R}{J}$

(3) $\dfrac{C_P} {C_V } = \dfrac{R}{J}$

(4) $C_V - C_P = \dfrac{R}{J}$

17> R defined by the ratio $\dfrac{C_P}{C_V}$ is always

(1) Negative

(2) 1

(3) Positive but less than 1

(4) Positive but more than 1

18>Molar specific heat at constant volume CV for a diatomic gas is

(1) $\dfrac{3}{2} R$

(2) $\dfrac{5}{2} R$

(3)  3 R

(4) 4 R

19>The molar specific heat at constant pressure CP for a monoatomic gas is

(1) $\dfrac{3}{2} R$

(2) $\dfrac{5}{2} R$

(3) $\dfrac{7}{2} R$

(4) 4 R

20>The following sets of values of CP and CV a gas have been reported by different student. The units are cal/g-mol K; which of the following sets is most reliable ?

(1) CV =3, CP =5

(2) CV =4, CP =6

(3) CV =3, CP =2

(4) CV =3, CP =4.2

21>The triple point of a substance

(1) Is unique

(2) Has two values

(3) Have three values

(4) Does not exist

22>The triple point of a water is

(1) 273 K

(2) 373 K

(3) 273.16 K

(4) 273.15 K

23>If R is a gas constant and CP, CV are specific heats of a solid per mole, then for the solid

(1) $C_P - C_V = R$

(2) $C_P - C_V << R$

(3) $C_P - C_V = 0$

(4) $C_P - C_V is \, negative$

24>If R is a gas constant and CP , CV are specific heats of a water between 0°C and 4°C, then

(1) $C_P - C_V = R$

(2) $C_P - C_V << R$

(3) $C_P - C_V = 0$

(4) $C_P - C_V$is negative

25>If one mole of a monatomic gas is mixed with one mole of a diatomic gas, the value of molar specific heat at constant volume CV will be

(1) $\dfrac{3}{2} R$

(2) $\dfrac{5}{2} R$

(3) 2 R

(4) Uncertain

26> If one mole of a monatomic gas is mixed with 1 mole of a diatomic gas, then the value
of $\gamma = \dfrac{C_P}{C_V}$ for the mixture will be

(1) $\dfrac{5}{3} R$

(2) $\dfrac{7}{5} R$

(3) $\dfrac{4}{3} R$

(4) 1.5

27>Isothermal change of a perfect gas, which of the following is true?

(1) $PV^{\gamma}$ = constant

(2) $PV {\gamma}^{V}$ = constant

(3) $(PV)^{\gamma}$= constant

(4) PV = constant

28>For an adiabatic change of a perfect gas, which of the following is true?

(1) $PV^{\gamma}$ = constant

(2) $PV {\gamma}^{V}$ = constant

(3) $(PV)^{\gamma}$= constant

(4) PV = constant

29> For an adiabatic change of a perfect gas, which of the following is true?

(1) $PV^{\gamma}$ = constant

(2) $TV^{\gamma - 1}$ = constant

(3) $T^{\gamma - 1} V$ = constant

(4) $T^{\gamma} V^{\gamma - 1}$ = constant

30>For a given mass of a gas in an adiabatic change, the temperature and pressure are related according to the law

(1) $\dfrac{P}{T}$ = constant

(2) $T^{\gamma} P^{1 - \gamma}$ = constant

(3) $PT^{\gamma}$ = constant

(4) $P^{\gamma} T^{1 - \gamma}$ = constant

31> Compressed air in a tube of a wheel of a cycle at normal temperature suddenly starts coming out of a puncture. This is an example of

(1) Isothermal process

(3) Isochoric process

(4) Isothermal -Isobaric process

32>Compressed air in a tube of a wheel of a cycle at normal temperature suddenly starts coming
out of a puncture. Then the air inside

(1) Starts becoming hot

(2) Starts becoming cool

(3) Remains at the same temperature

(4) May become hotter or cooler depending upon the amount of water-vapour present

33>For a monatomic gas in adiabatic process, the relation between the pressure and absolute temperature T is

$P \propto T^{C}$ where c is equal to

(1) $\dfrac{5}{3}$

(2) $\dfrac{2}{5}$

(3) $\dfrac{3}{5}$

(4) $\dfrac{5}{2}$

34>The number of degrees of freedom for a diatomic gas molecule is

(1) 2

(2) 3

(3) 5

(4) 6

35>A polyatomic gas with n-degrees of freedom has a mean energy per molecule given by

(1) $\dfrac{n k T}{N}$

(2) $\dfrac{n k T}{2N}$

(3) $\dfrac{n k T}{2}$

(4) $\dfrac{3 k T}{2}$

36>An ant is moving on a horizontal floor. The degrees of freedom associated with the motion
of the ant is

(1) 1

(2) 2

(3) 3

(4) 5

37>A fly is flying in space, the degrees of freedom associated with the motion of the fly is

(1) 1

(2) 2

(3) 3

(4) 5

38>If dQ heat supplied, dU the change in internal energy and dW the work done by the gas, then the first law of thermodynamics states

(1) dQ = dU – dW

(2) dU = dQ – dW

(3) dU = dW – dQ

(4) dQ + dU + dW = 0

39>The first law of thermodynamics confirms the law of

(1) Conservation of momentum

(2) Conservation of energy

(3) Flow of heat in a particular direction

(4) Conservation of energy

40>The first law of thermodynamics is concerned with the conservation of

(1) Number of molecules

(2) Number of moles

(3) Temperature

(4) Energy

41>The second law of thermodynamics is concerned with the

(1) Conservation of energy

(2) Conservation of number of moles

(3) Transformation of heat energy into work

(4) Conservation of temperature

42>If is dQ heat supplied, dU the change in internal energy and T the absolute temperature, then the mathematical form of the second law of thermodynamics is

(1) dQ = $\dfrac{dU}{T}$

(2) dQ = $\dfrac{dS}{T}$

(3) dQ = T dS

(4) dQ = $\dfrac{T}{dS}$

43> For a gas $\dfrac{R}{C_V}$ = 0.67 , this gas is made up of molecules which are

(1) Diatomic

(2) Monatomic

(3) Polyatomic

(4) Mixture of diatomic and poly atomic molecules

44>What is the value of $\dfrac{R}{C_P}$ for a diatomic gas

(1) $\dfrac{5}{7}$

(2) $\dfrac{2}{7}$

(3) $\dfrac{3}{5}$

(4) $\dfrac{3}{4}$

45>The equation of state of an ideal gas for molecules is
(k =Boltzmann constant, R =gas constant)

(1) PV = RT

(2) PV = Nrt

(3) PV = nkt

(4) nPV = RT

46>The equation of state corresponding to 8 grams of oxygen is

(1) PV = 8RT

(2) PV = RT

(3) PV = $\dfrac{RT}{2}$

(4) PV = $\dfrac{RT}{4}$

47>The work done in isothermal expansion from volume V1 to V2 at temperature T for 1 mole of an ideal gas is

(1) $P_1 V_1 {\log} _e \dfrac{V_2}{V_1}$

(2) $\dfrac{P_1} {V_1} {\log} _e \dfrac{V_2}{V_1}$

(3) $P_1 V_1 {\log} _e \dfrac{V_1}{V_2}$

(4) $\dfrac{R}{ T }{\log} _e \dfrac{V_2}{V_1}$

48>A gas expands under constant pressure P from volume V1 to V2. The work done by the gas

(1) P(V_2 – V_1)

(2) $P ( V_1^{\gamma} - V_2^{\gamma}$

(3) P ( V_1 – V_2 )

(4) $\dfrac{P V_1 V_2}{V_2 - V_1}$

49>A gram-mole of-an ideal gas expands isothermally at a temperature T from an initial volume V1 to a final volume V2 (V2 >V1). Then the work done by the gas is

(1) $RT {\log} _e \dfrac{V_2}{V_1}$

(2) $RT \dfrac{V_2}{V_1}$

(3) $\dfrac{V_2}{V_1} {\log}_e RT$

(4) RT ${\log}_e ( V_2 - V_1 )$

50>A gram-mole of an gas expands adiabatically from an initial temperature T1 to a final temperature T2 (T1 >T2), then the work done by the gas is

(1) $\dfrac{C_V}{\gamma - 1} [ T_1 - T_2 ]$

(2) $R [ T_1 - T_2 ]$

(3) $\dfrac{R}{\gamma - 1} [ T_2 - T_1 ]$

(4) $\dfrac{R}{\gamma - 1} [ T_1 - T_2 ]$

51>The work done in an isothermal expansion of a gas depends upon

(1) Temperature only

(2) Expansion ratio only

(3) Both temperature and expansion ratio

(4) Neither temperature nor expansion ratio

52>The work done in an adiabatic expansion of a gas depends upon

(1) Difference of initial and final temperatures only

(2) Expansion ratio only

(3) Difference of initial and final temperatures and expansion ratio both

(4) Neither difference of initial and final temperatures nor expansion ratio

53>A point on P-V a diagram represents

(1) Work done in a cyclic process

(2) A thermodynamic process

(3) Heat supplied to system

(4) The state of a thermodynamic system

54>The area under diagram represents

(1) Work done by the system.

(2) A thermodynamic process.

(3) Change of internal energy of the system

(4) Heat supplied to system

55>The internal energy of an ideal gas depends upon

(1) Temperature

(2) Pressure

(3) Volume

(4) Temperature and volume both

56>The internal energy of a real gas depends upon

(1) Temperature

(2) Pressure

(3) Volume

(4) Temperature and volume both

57>A sample of gas expands from volume V1 to volume V2. The amount of work done by the
gas is greatest when the expansion is

(1) Isothermal

(2) Isobaric

(4) Equal in all above cases

(58) In the following diagram which process is adiabatic

(1) a

(2)  b

(3) c

(4) d

59>Mean kinetic energy per gram mole of an ideal diatomic gas is

(1) $\dfrac{1}{2} RT$

(2) $\dfrac{3}{2} RT$

(3) $\dfrac{5}{2} R$

(4) 3 RT

60>A quantity of air ($\gamma$ = 1.4) at 27°C is compressed slowly, the temperature of the air-system will

(1) Fall

(2) Rise

(3) Remain unchanged

(4) First rise and then fall

61>A quantity of air ($\gamma$ = 1.4)  at 27°C is compressed suddenly, the temperature of the air system will

(1) Fall

(2) Rise

(3) Remain unchanged

(4) First rise and then fall

62>Heat can not be wholly converted into work. This law was enunciated by

(1) Kelvin and Planck

(2) Clasius

(3) Einstein

(4) Joule and Thomson

63>Heat cannot flow from a cold body to hot body without the aid of any external agency. This law was enunciated by

(1) Kelvin and Planck

(2) Clausius

(3) Einstein

(4) Joule and Thomson

64>In a reversible isochoric change

(1) $\triangle W = 0$

(2) $\triangle P = 0$

(3) $\triangle T = 0$

(4) $\triangle U = 0$

65> The ratio of slope of adiabatic curve to isothermal curve of a gas is $\gamma = \dfrac{C_P}{C_V}$

(1) $\gamma$

(2) $\dfrac{1}{\gamma}$

(3) 1

(4) $\gamma - 1$

66>The volume of a real gas is V at a pressure P. On increasing the pressure by $\triangle$P.  the change in the volume of the gas is $\triangle V_1$ under isothermal conditions and $\triangle V_2$  under adiabatic conditions, then  $\gamma = \dfrac{C_P}{C_V}$

(1) $\dfrac{\triangle V_1}{\triangle V_2} = \gamma$

(2) $\dfrac{\triangle V_1}{\triangle V_2} = 1$

(3) $\dfrac{\triangle V_1}{\triangle V_2} = \dfrac{1}{\gamma}$

(4) $\dfrac{\triangle V_1}{\triangle V_2} = \dfrac{1}{\gamma - 1}$

67>For a certain mass of the isothermal curves between P and V at T1 and T2 temperature are
1 and 2 shown in fig. Then

(1) T1 = T2

(2) T1 < T2

(3) T1 > T2

(4) Nothing can be predicted

68>The change in volume V with respect to increase in pressure P is shown in fig. for a non-ideal gas at four different temperatures T1, T2, T3 and T4. The critical temperature of the gas is

(1) T1

(2) T2

(3) T3

(4) T4

(69) A gas is at a temperature which is above critical temperature. Then the gas

(1) May be liquefied by increasing pressure steadily

(2) May liquefied by decreasing pressure

(3) May be liquefied by increasing pressure suddenly

(4) Cannot be liquefied at all

70>The value of the critical temperature in terms of Vander Waal’s constants ‘a’ and ‘b’ is given by

(1) $T_C = \dfrac{8a}{27Rb}$

(2) $T_C = \dfrac{2a}{Rb}$

(3) $T_C = \dfrac{a}{2Rb}$

(4) $T_C = \dfrac{a}{Rb}$

71>In Vander Waal’s equation, the critical pressure PC is given by

(1) 3b

(2) $\dfrac{a}{27b^2}$

(3) $\dfrac{27a}{b^2}$

(4) $\dfrac{27b^2}{a}$

72>The critical volume of a gas obeying Vander Waal’s equation is

(1) $\dfrac{8a}{27 Rb}$

(2) $\dfrac{a}{27b^2 R}$

(3) 3b

(4) $\dfrac{a}{27R}$

73>Work done by a system is zero in

(1) Isothermal process

(3) Isochoric process

(4) Isobaric process

74>Milk is poured in a cup of tea and is mixed with a spoon. This is an example of

( 1) Reversible process

(2) Irreversible process

(4) Isothermal process

75>A thermodynamic system undergoes a cyclic process ABCDA shown in fig. The work done in the complete cycle is

(1) PV

(2) 2 PV

(3) $\dfrac{1}{2}$

(4) 0

76> An ideal gas is taken around the cycle ABCA

as shown on PV diagram. The net work done by the gas during the cycle is equal to

(1) P1V1

(2)  3 P1V1

(3) 6 P1V1

(4) 12 P1V1

77>An ideal gas is taken around a cycle ABCA on a diagram The net work done by the gas during the cycle is equal to

(1) 12 P1V1

(2) -12 P1V1

(3) – 6P1V1

(4) 6 P1V1

78> If the amount of heat given to a system be 35 J and the amount of work done by the system be -15 J, then the change in internal energy of the system is

(1) -50 J

(2)50 J

(3) 20 J

(4) -20 J

79>If the amount of heat liberated by the system be 40 J and the work done by the system be 10 J, then the change in internal energy of the system is

(1) -50 J

(2) 50 J

(3) 30 J

(4) -30 J

80>If the amount of heat energy given to system be 40 J and the amount of work done on the system be 10 J; then the change in internal energy of the system will be

(1) -50 J

(2) 50 J

(3) 30 J

(4) -30 J

81>An ideal gas is taken around the cycle ABDCA; the change in internal energy of the gas will be

(1) 2P1 V1

(2) -2P1 V1

(3) 4P1 V1

(4) Zero

82>The curve in the adjoining fig. shows an isothermal expansion of a given mass of a gas. The area under the curve is divided into two regions. The region 1 is from A to B and the region 2 is from B to C. If the work done in the two regions be denoted by W1 and W2 respectively, then it may be concluded

(1) W1 > W2

(2) W1 < W2

(3) W1 = W2

(4) W1 and W2 cannot be compared

83> Two samples A and B of a gas initially at the same temperature and pressure are compressed from volume V to $\dfrac{V}{2}$ (A isothermally and B adiabatically), the final pressure of

(1) A is greater than that B

(2) A is equal to that of B

(3) A is less than that of B

(4) A is twice that of B

84>Which one of the following is independent path between given initial and final states

(1) Heat supplied to system

(2) Work done by system

(3) Change in internal energy of system

(4) All of above

85>A system changes from state (P1, V1) to state(P2, V2) as shown in fig. The work done by the system is

(1) $8 \times 10^5$ J

(2) $6 \times 10^5$ J

(3) $12 \times 10^5$ J

(4) $7.5 \times 10^5$ J

86> Water falls from a height of 42 m. Assuming that all the energy is converted into heat, the rise in temperature of water will be ( 4.2 X 103 J/kilocal and specific heat of watt 1 kilocal /kg°C, g =10 m/s2)

(1) 0.01°C

(2) 0.1°C

(3) 1°C

(4) 10°C

87>An iron piece falls from a height of 1 km on the ground. If all the energy is converted into heat ; the rise of temperature of the iron piece will be (specific heat of iron = 0.1 kilocal /kg oC)

(1) 0.33°C

(2) 2.33°C

(3) 23.3°C

(4) 233°C

88>From what height a block of ice must fall into a well so that $\dfrac{1}{100}$ th of its mass may be melted .The temperature of water in the well is 0°C. Latent heat of fusion of ice is 80 kilocal/kg

(1) 3.42 m

(2) 34.2 m

(3) 342 m

(4) 3420 m

89>A perfect gas ($\gamma$ = 1.5) is compressed to one fourth of its original volume. If initial pressure of the gas is 1 atmosphere and the compression be isothermal, then the final pressure will be

(1) 4 atm

(2) $\dfrac{1}{4}$  atm

(3) 16 atm

(4) $\dfrac{1}{16}$  atm

90>In Q.89, if the compression be adiabatic, then the final pressure will be

(1) 2 atm

(2) 4 atm

(3) 8 atm

(4) 16 atm

91>A litre of air at 76 cm of Hg pressure is compressed to a pressure of 120 cm of Hg under isothermal conditions. The new volume is

(1) 76 cc

(2) 196 cc

(3) 633.3 cc

(4) 1000 cc

92>0.93 Watt hour energy is supplied to a block of ice weighting 10g. It is found that

(1) Half of the block melts

(2) The entire block just melts

(3) The entire block melts and the water attains a temperature of 4°C

(4) The block remains unmelted.

93>The pressure and density of an adiabatic gas $\gamma = \dfrac{7}{5}$ change adiabatically from (P, d) to (P’, d’). If  $\dfrac{d'}{d}$ = 32, then $\dfrac{P'}{P}$; should be

(1) 32

(2) 128

(3) $\dfrac{1}{128}$

(4) None of these

94>The temperature of 5 moles of a gas which was held at constant volume was changed from 100°C to 120°C. The change in the internal energy of the gas was found to be 80 J; the total heat capacity of the gas at constant volume will be equal to

(1) 8 J/K

(2) 0.8 J/K

(3) 4.0

(4) 0.4 J/K

95>When an ideal diatomic gas is heated at constant pressure, the fraction of the heat energy supplied which increases the internal energy of the gas is

(1) $\dfrac{2}{5}$

(2) $\dfrac{3}{5}$

(3) $\dfrac{3}{7}$

(4) $\dfrac{5}{7}$

96>During an adiabatic expansion of 2 moles of gas, the change in internal energy was found to be -50J. The work done during the process will be

(1) 50 J

(2) -50 J

(3) 100 J

(4) Zero

97>In a certain gas, the ratio of specific heat is given by $\gamma = 1.5$.For this gas

(1) $C_V = \dfrac{3R}{J}$

(2) $C_P = \dfrac{3R}{J}$

(3) $C_P = \dfrac{5R}{J}$

(4) $C_V = \dfrac{5R}{J}$

98> If the degrees of freedom of gas are f, the ratio of its specific heats $\dfrac{C_P}{C_V}$ is given by

(1) $1 + \dfrac{2}{f}$

(2) $1 - \dfrac{2}{f}$

(3) $1 + \dfrac{1}{f}$

(4) $1 - \dfrac{1}{f}$

99>A given mass of gas is taken from state A to B by two paths ACB and ADB successively  denoted by 1 and 2 .If the work done are W1 and W2 along paths ,then

(1) W1 = W2

(2) W1 > W2

(3) W1 < W2

(4) W1 and W2 cannot be compared

100>1 mole of a monatomic gas is first heated at constant volume by 100°C. The change in internal energy of the gas is $\triangle U_1$. Next it is heated at constant pressure by 100°C, the change in internal energy of the gas is $\triangle U_2$. Then the ration $\dfrac{Q_1}{Q_2}$ =

(1) 1

(2) $\dfrac{3}{5}$

(3) $\dfrac{5}{3}$

(4) Uncertain

101>1 mole of a monatomic gas is first heated at constant volume by 100°C. The heat absorbed by the gas is $Q_1$. Next it is heated at constant pressure; the heat absorbed by the gas is Q2.
Then the ratio $\dfrac{Q_1}{Q_2}$ =

(1) 1

(2) $\dfrac{3}{5}$

(3) $\dfrac{5}{3}$

(4) Uncertain

102>Temperature of argon kept in a vessel is raised by 1°C at constant volume. Heat supplied to the gas may be taken partly as translational and partly as rotational kinetic – energies. Their respective shares are

(1) 60%, 40%

(2) 40%, 60%

(3) 50%, 50%

(4) 100%, 0%

103>Temperature of oxygen kept in a vessel is raised by 1°C at constant volume. Heat supplied to gas may be taken partly as translational and partly as rotational kinetic energies. Their respective shares are

(1) 60%, 40%

(2) 40%, 60%

(3) 50%, 50%

(4) 100%, 0%

104>If T1 and T2 are temperatures of source and sink in Kelvin and t1 and t2 are the corresponding temperatures then the efficiency of Carnot engine is

(1) $1 - \dfrac{t_1}{t_2}$

(2) $1 - \dfrac{T_1}{T_2}$

(3) $1 - \dfrac{t_2}{t_1}$

(4) $1 - \dfrac{T_2}{T_1}$

105>The efficiency of Carnot engine operating between reservoirs at temperatures 100°C and -23o C will be

(1) $\dfrac{100 - 23}{273}$

(2) $\dfrac{100 + 23}{373}$

(3) $\dfrac{100 + 23}{100}$

(4) $\dfrac{100 - 23}{100}$

106>The source and sink temperature of a Carnot engine are 400K and 300K respectively. What
is the efficiency

(1) 100%

(2) 75%

(3) 33.3%

(4) 25%

107>If the temperature of the source is increased ,the efficiency of the Carnot engine

(1) Increases

(2) Decreases

(3) Remains unchanged

(4) First increases and then becomes constant

108>If the temperature of the sink is increased, the efficiency of the Carnot engine

(1) Increases

(2) Decreases

(3) Remains unchanged

(4) First increases and then becomes constant

109>Which is more effective for increasing the efficiency of Carnot engine

(1) Increasing temperature of source by 100°C

(2) Decreasing temperature of sink by 100°C

(3) Increasing temperature of source by 50°C

(4) All above are equally effective.

110>An ideal gas heat engine operates in a Carnot cycle between 227°C and 127°C. It absorbs
6.0 X 104 cal at the higher temperature. The amount of heat converted into work is equal to

(1) $1.2 \times 10^4$ cal

(2) $1.6 \times 10^4$ cal

(3) $3.5 \times 10^4$ cal

(4) $4.8 \times 10^4$ cal

111>The coefficient of performance of a Carnot refrigerator working between 30°C and 0°C is

(1) Zero

(2) 0.1

(3) 9

(4) 10

112>110 J of heat is added to a gaseous system whose internal energy increases by 40 J, then the amount of external work done is

(1) 40 J

(2) 70 J

(3) 110 J

(4) 150 J

113>The temperature of a gas is raised from 27°C to 927°C. The root mean square speed of molecules

(1) Gets halved

(2) Gets doubled

(3) Remains unchanged

(4) Gets times the earlier speed

114>Relation between pressure P and energy E per unit volume of a gas is

(1) $P = \dfrac{2}{3} E$

(2) $P = \dfrac{E}{3}$

(3) $P = \dfrac{3}{2} E$

(4) P = 3E

115>The change in internal energy per g-mole of an ideal gas when its temperature is raised by $\triangle$ T is

(1) $\dfrac{R \triangle T}{\gamma - 1}$

(2) $\dfrac{R }{\gamma} \triangle T$

(3) $\dfrac{\gamma - 1} {R}\triangle T$

(4) $\dfrac{R \triangle T}{\gamma + 1}$

116>When water is heated from 10°C to 20°C,

(1) CP = CV

(2) CP < CV

(3) CP – CV << R

(4) CP – CV = R

117>The temperature of an ideal gas is increased from 120 K to 480 K. If at 120 K the root mean square speed of gas molecule is v, at 480 K it becomes

(1) 4 v

(2) 2 v

(3) $\dfrac{v}{2}$

(4) $\dfrac{v}{4}$

118>The speed of rotation of a fan is increased, the temperature of air inside the room

(1) Decreases

(2) Increases

(3) Remains the same

(4) First increases and then decreases and attains the original value

119>The ratio of root mean square speeds of hydrogen and oxygen at the same temperature is

(1) 1 : 4

(2) 4 : 1

(3)8:1

(4)16:1

120>The root mean square speed of hydrogen at 27°C is

(1) 1116 m/s

(2) 111.6 m/s

(3) 3.52 m/s

(4) 352 m/s

121>The ratio of translational KE of O2 and N2 at the same temperature is in the ratio

(1) 1 : 1

(2) 16 : 14

(3) 14 : 16

(4) $\sqrt{16} \sqrt{14}$

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