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A Carnot engine converts $\frac{1}{5}$ of the available heat into work. Keeping the temperature of the reservoirs the same, two Carnot engines are used to replace the single Carnot engine: the heat ejected by the first is equal to the heat input to the second and the heat ejected by the second is to the lower reservoir. The efficiency of the second engine is $9.09 %$ (i.e. $\frac{1}{11}$ ). The efficiency of the first engine is

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Important Questions on Heat and Thermodynamics

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Physics>Heat and Thermodynamics>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

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

EASY

Physics>Heat and Thermodynamics>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

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

MEDIUM

Physics>Heat and Thermodynamics>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

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,

HARD

Physics>Heat and Thermodynamics>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

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.

EASY

Physics>Heat and Thermodynamics>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

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:

MEDIUM

Physics>Heat and Thermodynamics>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

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>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

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>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

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>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

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>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

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>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

The efficiency of a Carnot engine depends upon

EASY

Physics>Heat and Thermodynamics>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

The efficiency of an ideal heat engine working between the freezing point and boiling point of water, is

MEDIUM

Physics>Heat and Thermodynamics>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

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?

EASY

Physics>Heat and Thermodynamics>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

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)

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Physics>Heat and Thermodynamics>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

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

Question Image

MEDIUM

Physics>Heat and Thermodynamics>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

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>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

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}

EASY

Physics>Heat and Thermodynamics>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

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

MEDIUM

Physics>Heat and Thermodynamics>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

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:

Question Image

MEDIUM

Physics>Heat and Thermodynamics>Heat and Thermodynamics>Carnot Engine Efficiency and Coefficient of Performance

A Carnot's engine works like a refrigerator between

250 K

and

300 K

. It receives

500 cal

heat from the reservoir at a lower temperature. The amount of work done in each cycle to operate the refrigerator is,

Important Questions on Heat and Thermodynamics

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