NEET Physics : Thermodynamics

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

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

Two heater wires, made of the same material and having the same length and the same radius, are first connected in series and then in parallel to a constant potential difference. If the rates of I heat produced in the two cases are H_s  and  H_P respectively, then  H_s/H_P  will be

• 1/2

• 2

• 1/4

• 4

In an adiabatic change , the pressure and temperature of a monoatomic gas are relted as P ∝ T^C, where C equals

• $\frac{2}{3}$

• $\frac{5}{2}$

• $\frac{3}{5}$

• $\frac{5}{3}$

By sucking through a straw, a student can reduce the pressure in his lungs to 750 mm of Hg ( densiy = 13.6 g/cm³). Using the straw, he can drink water from a glass upto a maximum depth of

• 10 cm

• 75 cm

• 13.6 cm

• 1.36 cm

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:  In free expansion of an ideal gas, the entropy increases. 

Reason:  Entropy increases in all natural processes.

• 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 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

When you make ice cubes, the entropy of water

• does not change

• increase

• decreases

• may either increase or decrease depending on the process used

Assertion: Ferro magnetic substances become paramagnetic above Curie temperature.

Reason: Domains are destroyed at high temperature.

• 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