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Kelvin Planck's law deal with

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Important Questions on Thermodynamics

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Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

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>Thermodynamics>Second Law of Thermodynamics

By leaving the door of a small standard domestic refrigerator open, it is not possible to cool a room, because it violates the ______

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Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

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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Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

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}

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Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

Entropy of the universe tends to be

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Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

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

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

For which of the following processes, entropy change is zero?

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Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

An ideal Carnot's engine works between

227 °

and

57 ° C

. Find the efficiency of the engine.

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Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

Consider a two stage Carnot engine. In the first stage heat

Q_{1}

is absorbed at temperature

T

and heat

Q_{2}

is expelled at temperature

α T

(where

α < 1

). In the second stage heat

Q_{2}

is absorbed at temperature

α T

and heat

Q_{3}

is expelled at temperature

β T (β < α) .

The efficiency of the Carnot engine will be

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Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

The carnot heat engine have an efficiency of

50 % .

The temperature of sink is maintained at

500 K .

To increase the efficiency upto

80 %,

the increment in the source temperature is

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Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

The efficiency of Carnot engine is

0.6

. It rejects

20 J

of heat to sink. The work done by the engine is

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Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

One mole of an ideal monatomic gas undergoes the following four reversible processes:
Step

1 :

It is first compressed adiabatically from volume

V_{1}

1 m^{2} .

Step

2 :

then expanded isothermally to volume

10 m^{3}

Step

3 :

then expanded adiabatically to volume

V_{3}

Step

4 :

then compressed isothermally to volume

V_{1} .

If the efficiency of the above cycle is

\frac{3}{4}

then

V_{1}

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Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

A Carnot engine takes

300

calories of heat from a source at

500 K

and rejects

150

calories of heat to the sink. The temperature of the sink is

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Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

The efficiency of a Carnot engine depends upon

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Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

For a Carnot engine which of the following is false?

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Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

The following figure shows a Carnot engine that works between temperatures

T_{1} = 400 K

and

T_{2} = 200 K

and drives a Carnot refrigeration that works between temperatures

T_{3} = 350 K

and

T_{4} = 250 K .

The quantity

\frac{Q_{3}}{Q_{1}}

will be

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Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

A number of carnot engines are operated at identical cold reservoir temperatures $(T_{L})$ . However, their hot reservoir temperatures are kept different. A graph of the efficiency of the engines versus hot reservoir temperature $(T_{H})$ is plotted. The correct graphical representation is

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Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

What will be the efficiency of a Carnot engine if it takes heat from reservoir, at

100 ° C

and rejects heat to a sink at,

50 ° C

HARD

Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

Graphs below show the entropy versus energy $U$ of two systems $1$ and $2$ at constant volume. The initial energies of the systems are indicated by $U_{1, i}$ and $U_{2, i},$ respectively. Graphs are drawn to the same scale. The systems are then brought into thermal contact with each other. Assume that, at all times the combined energy of the two systems remains constant. Choose the most appropriate option indicating the energies of the two systems and the total entropy after they achieve the equilibrium.

Question Image

HARD

Physics>Heat and Thermodynamics>Thermodynamics>Second Law of Thermodynamics

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.

Kelvin Planck's law deal with

Important Questions on Thermodynamics

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