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

MEDIUM

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An idealized diesel engine operates in a cycle known as air standard diesel cycle as shown. Fuel is sprayed into the cylinder at the the point of maximum compression $B$ . Combustion occurs during expansion $B C$ .

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Important Questions on Thermodynamics

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines

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:

HARD

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines

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>Thermodynamics>Heat Engines

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

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

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>Heat Engines

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

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>Thermodynamics>Heat Engines

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

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines

A car engine has a power of

20 kW

. The car makes a roundtrip of 1 hour. If the thermal efficiency of the engine is

40 %

and the ambient temperature is

300 K

. The energy generated by fuel combustion is

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines

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

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines

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:

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines

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

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines

An engine operates by taking a monatomic ideal gas through the cycle shown in the figure. The percentage efficiency of the engine is close to

Question Image

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines

A Carnot engine operates between two reservoirs of temperatures

900 K

and

300 K

. The engine performs

1200 J

of work per cycle. The heat energy (in

J

) delivered by the engine to the low temperature reservoir, in a cycle, is _____________

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines

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>Thermodynamics>Heat Engines

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>Thermodynamics>Heat Engines

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>Heat Engines

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,

MEDIUM

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines

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

EASY

Physics>Heat and Thermodynamics>Thermodynamics>Heat Engines

Entropy of the universe tends to be

An idealized diesel engine operates in a cycle known as air standard diesel cycle as shown. Fuel is sprayed into the cylinder at the the point of maximum compression B. Combustion occurs during expansion BC.

Important Questions on Thermodynamics

Learn and Prepare for any exam you want !

An idealized diesel engine operates in a cycle known as air standard diesel cycle as shown. Fuel is sprayed into the cylinder at the the point of maximum compression $B$ . Combustion occurs during expansion $B C$ .