Thermodynamics

Assertion:  Water kept in an open vessel will quickly evaporate on the surface of the moon. 

Reason:  The temperature at the surface of the moon is much higher than boiling point of 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.

Assertion:  For  an  isothermal  process  in  an  ideal  gas,  the heat  obsorbed  by the  gas is  entirely  used   in  the  work  done  by  the  gas. 

Reason:  During  a  process  taking  place in  a  system, the temperature remains constant then the  process is isothermal.

• 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

A slab consists of two layers of different materials of the same thickness and having thermal conductivities  K₁ and K₂  are connected in series. The equivalent thermal conductivity of the slab is

• $\frac{2 {\mathrm{K}}_1 {\mathrm{K}}_2}{{\mathrm{K}}_1 + {\mathrm{K}}_2}$

• $\sqrt{{\mathrm{K}}_1 {\mathrm{K}}_2}$

• $\frac{{\mathrm{K}}_1 {\mathrm{K}}_2}{{\mathrm{K}}_1 + {\mathrm{K}}_2}$

• K₁ + K₂

A certain gas is taken to the five states represented by dots in the graph. The plotted lines are isotherms. Order of the most portable speed ν_p of the molecules at these five states is

• ν_{p at 3}  > ν_{p at 1} = ν_{p at 2} > ν_{p at 4} = ν_{p at 5}

• ν_{p at 1} > ν_{p at 2} =  ν_{p at 3} > ν_{p at 4} > ν_{p at 5}

• ν_{p at 3} > ν_{p at 2} = ν_{p at 4} > ν_{p at 1} = ν_{p at 5}

• insufficient information to predict the result

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

• $\frac{2}{3}$

• $\frac{5}{2}$

• $\frac{3}{5}$

• $\frac{5}{3}$

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

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

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

When you make ice cubes, the entropy of water

• does not change

• increase

• decreases

• may either increase or decrease depending on the process used