Q.

Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : With the increase in the pressure of an ideal gas, the volume falls off more rapidly in an isothermal process in comparison to the adiabatic process.

Reason (R) : In isothermal process, PV = constant, while in adiabatic process PVγ = constant. Here γ is the ratio of specific heats, P is the pressure and V is the volume of the ideal gas.

In the light of the above statements, choose the correct answer from the options given below:          [2025]

1 Both (A) and (R) are true but (R) is NOT the correct explanation of (A)  
2 (A) is true but (R) is false  
3 Both (A) and (R) are true and (R) is the correct explanation of (A)  
4 (A) is false but (R) is true  

Ans.

(4)

For isothermal process

PV = constant

 PdV+VdP=0

 dVV=dPP

 dV=(VP)dP

For adiabatic PVγ = constant

 PγVγ1dV+VγdP=0

 dV=VγP(dP)

Magnitude of |VP| is greater than |VγP|

So, volume falls more rapidly in adiabatic.

2nd statement is the process description of the isothermal and adiabatic.