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(a)

Discuss how the second law of thermodynamics applies to the situation of the room cooling down.

[ 2 ]
[Maximum number: 1]

A heat engine does 300 J of work during one cycle. In this cycle 900 J of energy is wasted. What is the efficiency of the engine?

A

0.25

B

0.33

C

0.50

D

0.75

In the P-V diagram below, which line could represent an adiabatic change for an ideal gas?

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[Maximum number: 1]

An ideal gas undergoes adiabatic expansion from state X to a new state of volume V. During this process the work done by the gas is W. What is the change in internal energy and the work done in an isothermal expansion of this gas from X to V ?

Change in

internal energy

Work done

0

greater than W

0

less than W

greater than 0

less than W

less than 0

same as W

[Maximum number: 1]

The entropy of a system

A

will decrease if the system's temperature is increased.

B

is related to the degree of disorder in the system.

C

must always increase.

D

is always conserved.

[Maximum number: 1]

The graph shows the variation of pressure P with volume V of an ideal gas during a thermodynamic cycle.

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During which stages is work done on the gas and work done by the gas?

Work done on gas

Work done by gas

X→YX \rightarrow Y only

Y→ZY \rightarrow Z only

X→YX \rightarrow Y and Z→XZ \rightarrow X

Y→ZY \rightarrow Z only

Y→ZY \rightarrow Z only

Z→XZ \rightarrow X and X→YX \rightarrow Y

Y→ZY \rightarrow Z only

X→YX \rightarrow Y only

[Maximum number: 1]

A fixed mass of gas is compressed in a very short period of time. Which of the following describes this process?

A

Adiabatic

B

Isobaric

C

Isochoric (isovolumetric)

D

Isothermal

[Maximum number: 1]

A block of ice at 0∘C0^{\circ} \mathrm{C} is placed on a surface and allowed to melt completely to give water at 0∘C0^{\circ} \mathrm{C}. During this process the entropy of the

A

molecules in the block has decreased.

B

surroundings has increased.

C

universe has increased.

D

universe has decreased.

[Maximum number: 1]

A fixed mass of an ideal gas undergoes an isochoric (isovolumetric) change. This increases the pressure of the gas. Which describes the change of internal energy of the gas and the direction of transfer of thermal energy?

Internal energy

Direction of transfer

of thermal energy

increase

to the gas

increase

from the gas

decrease

to the gas

decrease

from the gas

[Maximum number: 1]

The graph shows how the volume of a system varies with pressure during a cycle ABCA .

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What is the work done in joules during the change AB ?

A

15×10515 \times 10^{5}

B

9.0×1059.0 \times 10^{5}

C

4.5×1054.5 \times 10^{5}

D

0

0