Thermodynamics

A bimetallic strip consists of metals X and Y. It is mounted rigidly at the base as shown. The metal X has a higher coefficient of expansion compared to that for metal Y. When the bimetallic strip is placed in a cold bath

• it will bend towards the right

• it will bend towards the left

• it will not bend but shrink

• it will neither bend or shrink

Assertion:  In an isolated system the entropy increases. 

Reason: The processes in an isolated system are adiabatic.

• If both assertion and reason are true and reason is the correct explanation of the assertion

• If both assertion and reason are true but reason is not the correct explanation of the assertion

• If assertion is true, but reason is false

• Both assertion and reason are false statements

Assertion:  The Carnot cycle is useful in understanding the performance of heat engines. 

Reason:  The Carnot cycle provides a way of determining the maximum possible efficiency achievable with reservoirs of given temperatures.

• If both assertion and reason are true and reason is the correct explanation of the assertion

• If both assertion and reason are true but reason is not the correct explanation of the assertion

• If assertion is true, but reason is false

• Both assertion and reason are false statements

Assertion:  When a glass of hot milk is placed in a room and allowed to cool, its entropy decreases. 

Reason:  Allowing hot object to cool does not violate the second law of thermodynamics.

• If both assertion and reason are true and reason is the correct explanation of the assertion

• If both assertion and reason are true but reason is not the correct explanation of the assertion

• If assertion is true, but reason is false

• Both assertion and reason are false statement

Assertion: Reversible systems are difficult to find in real world. 

Reason : Most processes are dissipative in nature.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion: Air quickly leaking out of a balloon becomes cooler

Reason: The leaking air undergoes adiabatic expansion

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion:  In pressure-temperature (P-T) phase diagram of water, the slope of the melting curve is found to be negative. 

Reason:  Ice contracts on melting to water

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

N  moles of a monoatomic gas is carried round the reversible rectangular cycle ABCDA as shown in the diagram. The temperature at A  is T_o. The thermodynamic efficiency of the cycle is

• 15 %

• 50 %

• 20 %

• 25 %

Assertion: Thermodynamic process in nature are irreversible.

Reason: Dissipative effects cannot be eliminated.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion: When a bottle of cold carbonated drink is opened, a slight fog forms around the opening. 

Reason:  Adiabatic expansion of the gas causes lowering of temperature and condensation of water vapours.

• if both assertion and reason are true and the reason is the correct explanation of the assertion.

• if both assertion and reason are true and the reason is not  the correct explanation  of the assertion.

• if assertion is true but reason is false

• if both assertion and reason are false statements