Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R. Assertion A : Efficiency of a reversible heat engine will be highest at – 273 ° C temperature of cold reservoir. Reason R : The efficiency of Carnot’s engine depends not only on temperature of cold reservoir but it depends on the temperature of hot reservoir too and is given as η = 1 - T 2 T 1 In the light of the above statements, choose the correct answer from the options given below :

Both A and R are true and R is the correct explanation of A

Both A and R are true but R is NOT the correct explanation of A

HARD

JEE Main

IMPORTANT

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The specific heats, $C_{p}$ and $C_{v}$ of a gas of diatomic molecules, $A,$ are given (in units of $J m o l^{- 1} K^{- 1}$ ) by $29$ and $22,$ respectively. Another gas of diatomic molecules, $B,$ has the corresponding values $30$ and $21 .$ If they are treated as ideal gases, then:

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Important Questions on Thermodynamics

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JEE Main

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 10 - Thermodynamics>JEE Main - 9th January 2019 Shift 1>Q 59

A gas can be taken from

A

B

via two different processes

ACB

and

ADB

When path

ACB

is used

60 J

of heat flows into the system and

30 J

of work is done by the system. If the path

ADB

is used then work done by the system is

10 J

, the heat flows into the system in the path

ADB

is:

EASY

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IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 10 - Thermodynamics>JEE Main - 9th January 2019 Shift 2>Q 60

Two carnot engines

A

and

B

are operated in series. The first one,

A,

receives heat at

T_{1} (= 600 K)

and rejects to a reservoir at temperature

T_{2} .

The second engine

B

receives heat rejected by the first engine and, in turn, rejects to a heat reservoir at

T_{3} (= 400 K) .

Calculate the temperature

T_{2}

if the work outputs of the two engines are equal:

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EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 10 - Thermodynamics>JEE Main - 8th April 2019 Shift 2>Q 61

The given diagram shows four processes i.e., isochoric, isobaric, isothermal and adiabatic. The correct assignment of the processes, in the same order is given by:
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EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 10 - Thermodynamics>JEE Main - 10th April 2019 Shift 1>Q 62

n

moles of an ideal gas with constant volume heat capacity

C_{v}

undergo an isobaric expansion by certain volume. The ratio of the work done in the process, to the heat supplied is:

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EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 10 - Thermodynamics>JEE Main - 10th April 2019 Shift 1>Q 63

A cylinder with fixed capacity of

67.2

litre contains helium gas at STP. The amount of heat needed to raise the temperature of the gas by

20 ° C

is:
[Given that

R = 8.31 J m o l^{- 1} K^{- 1}]

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EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 10 - Thermodynamics>JEE Main - 10th April 2019 Shift 2>Q 64

When heat

Q

is supplied to a diatomic gas of rigid molecules, at constant volume its temperature increases by

∆ T

. The heat required to produce the same change in temperature, at a constant pressure is:

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EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 10 - Thermodynamics>JEE Main - 10th January 2019 Shift 1>Q 65

Three Carnot engines operate in series between a heat source at a temperature

T_{1}

and a heat sink at temperature

T_{4}

(see figure). There are two other reservoirs at temperature

T_{2}

and

T_{3},

as shown, with

T_{1} > T_{2} > T_{3} > T_{4} .

The three engines are equally efficient if:

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IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 10 - Thermodynamics>JEE Main - 10th January 2019 Shift 2>Q 66

2 kg

of a monoatomic gas is at a pressure of

4 \times 10^{4} N m^{- 2}

. The density of the gas is

8 kg m^{- 3}

. What is the order of energy of the gas due to its thermal motion?

The specific heats, Cp and Cv of a gas of diatomic molecules, A, are given (in units of J mol-1 K-1 ) by 29 and 22, respectively. Another gas of diatomic molecules, B, has the corresponding values 30 and 21. If they are treated as ideal gases, then:

Important Questions on Thermodynamics

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The specific heats, $C_{p}$ and $C_{v}$ of a gas of diatomic molecules, $A,$ are given (in units of $J m o l^{- 1} K^{- 1}$ ) by $29$ and $22,$ respectively. Another gas of diatomic molecules, $B,$ has the corresponding values $30$ and $21 .$ If they are treated as ideal gases, then: