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A diatomic ideal gas is used in a Carnot engine as the working substance. If during the adiabatic expansion part of the cycle, the volume of the gas increases from $V$ to $32 V$ . The efficiency of the engine is

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Important Questions on Thermodynamics

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

A heat engine is involved with exchange of heat of

1915 J, - 40 J, + 125 J

and

- Q J

, during one cycle achieving and efficiency of

50.0 %

. The value of

Q

is:

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

A Carnot freezer takes heat from water at

0^{o} C

inside it and rejects it to the room at a temperature of

27^{o} C .

The latent heat of ice is

336 \times 10^{3} J k g^{- 1} .

If 5kg of water at

0^{o} C

is converted into ice at

0^{o} C

by the freezer, then the energy consumed by the freezer is close to :

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

A Carnot engine having an efficiency of

\frac{1}{10}

is being used as a refrigerator. If the work done on the refrigerator is

10 J,

the amount of heat absorbed from the reservoir at a lower temperature is

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

Helium gas goes through a cycle $A B C D A$ (consisting of two isochoric and two isobaric lines) as shown in figure. The efficiency of this cycle is approximately

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MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

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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MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

A reservoir is at

827 ° C

and Carnot's engine takes a thousand

kilo calorie

of heat from it and exhausts it to a sink at

27 ° C

. What is the amount of work and the efficiency of the engine?

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

A Carnot engine has an efficiency of

\frac{1}{6} .

When the temperature of the sink is reduced by

62 ℃

, its efficiency is doubled. The temperatures of the source and the sink are, respectively,

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

Heat is flowing from a refrigerator whose inside temperature is

280 K

, to a room at

300 K

. Then the amount of heat delivered to the room for each joule of electrical energy consumed in joules is

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

A Carnot engine, having an efficiency of

η = \frac{1}{10}

as heat engine, is used as a refrigerator. If the work done on the system is

10 J

, the amount of energy absorbed from the reservoir at a lower temperature is:

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

The temperature inside a refrigerator is

t_{2}^{o} C

and the room temperature is

t_{1}^{o} C

. The amount of heat delivered to the room for each joule of electrical energy consumed ideally will be

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

The coefficient of performance of a refrigerator is

5

. If the temperature inside the freezer is

- 20 ° C

, the temperature of the surrounding to which it rejects heat is:

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

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:

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

Two carnot engines

A

and

B

are connected in series in such a way that the work outputs are equal when the temperatures of hot and cold reservoirs of

A

are

800 K

and

T

, and of engine

B

are

T

and

300 K

, respectively. Then the temperature

T

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

The efficiency of a Carnot engine depends upon

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

The efficiency of carnot engine is

η

when its hot and cold reservoirs are maintained at temperature

T_{1}

and

T_{2}

, respectively. To increase the efficiency to

1.5 η

, the increase in temperature

(Δ T)

of the hot reservoir by keeping the cold one constant at

T_{2}

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

A Carnot engine of efficiency

40 %,

takes heat from a source maintained at a temperature of

500 K

. It is desired to have an engine of efficiency

60 %

. Then, the source temperature for the same sink temperature must be

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

Freezing compartment of a refrigerator is at

0 ° C

and room temperature is

27.3 ° C

. Work done by the refrigerator to freeze

1 g

of water at

0 ° C

(L_{ice} = 80 cal g^{- 1})

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

A Carnot's engine having an efficiency of

\frac{1}{10}

as heat engine, is used as a refrigerator. If the work done on the system is

10 J,

the amount of energy absorbed from the reservoir at lower temperature is

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

A refrigerator works between

4^{o} C

and

30^{o} C

. It is required to remove

600

calories of heat every second in order to keep the temperature of the refrigerated space constant. The power required is:

(Take

1

cal =

4 .2

Joules)

HARD

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines and Refrigerators

A solid body of constant heat capacity

1 J {(℃)}^{- 1}

is being heated by keeping it in contact with reservoirs in two ways: (i) Sequentially keeping in contact with 2 reservoirs such that each reservoir supplies the same amount of heat. (ii) Sequentially keeping in contact with

8

reservoirs such that each reservoir supplies the same amount of heat. In both, cases the body is brought from initial temperature

100 K

to final temperature

200 K

. Entropy change of the body in the two cases respectively is: Note: This question was awarded as a bonus since temperatures were given in centigrade instead of in Kelvin. Proper corrections are made in the question to avoid it.

A diatomic ideal gas is used in a Carnot engine as the working substance. If during the adiabatic expansion part of the cycle, the volume of the gas increases from V to 32V. The efficiency of the engine is

Important Questions on Thermodynamics

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A diatomic ideal gas is used in a Carnot engine as the working substance. If during the adiabatic expansion part of the cycle, the volume of the gas increases from $V$ to $32 V$ . The efficiency of the engine is