An ice cube of mass 30 g at 0 0 C is left sitting on the kitchen table where it gradually melts and reaches the kitchen temperature of 25 0 C . The latent heat of fusion for ice is 333 J · g - 1 and the specific heat of water is 4 . 2 J · g - 1 · K - 1 . Select the correct statement(s) about this process. (All numerical values in the answers are rounded to the closest integer.)

The entropy of the kitchen does not change

The entropy change of the kitchen is - 48 J · K - 1

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A system undergoes a reversible adiabatic process. The entropy of the system

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Important Questions on Thermodynamics

EASY

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

A heat engine operates with the cold reservoir at temperature

324 K

. The minimum temperature of the hot reservoir, if the heat engine takes

300 J

heat from the hot reservoir and delivers

180 J

heat to the cold reservoir per cycle, is _____

K

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.

MEDIUM

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

An ice cube of mass

30 g

0^{0} C

is left sitting on the kitchen table where it gradually melts and reaches the kitchen temperature of

25^{0} C

. The latent heat of fusion for ice is

333 J \cdot g^{- 1}

and the specific heat of water is

4.2 J \cdot g^{- 1} \cdot K^{- 1}

. Select the correct statement(s) about this process. (All numerical values in the answers are rounded to the closest integer.)

MEDIUM

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

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

EASY

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

EASY

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

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)

MEDIUM

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

Two solid blocks at temperatures

T_{1}

and

T_{2} (T_{1} < T_{2})

are put in thermal contact for a long time inside an insulated container. Choose the correct statement(s).

EASY

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

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>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

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 ______

EASY

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:

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

EASY

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

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>Second Law of Thermodynamics

An engine operating between the boiling and freezing points of water will have

A. Efficiency more than $27 %$ .

B. Efficiency less than the efficiency of a Carnot engine operating between the same two temperatures.

C. Efficiency equal to $27 %$ .

D. Efficiency less than $27 %$ .

Choose the correct answer from the options given below

EASY

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

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:

MEDIUM

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

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>Second Law of Thermodynamics

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>Thermodynamics>Second Law of Thermodynamics

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

EASY

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

Entropy of the universe tends to be

MEDIUM

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}

A system undergoes a reversible adiabatic process. The entropy of the system

Important Questions on Thermodynamics

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