Question

For an adiabatic process,
A. $\Delta S=0$
B. $\Delta U=0$
C. Q=0
D. W= 0

Answer 1

Thermodynamics is a branch which describes the conversion of thermal energy to any other form of energy as well as their effects on matter. There are two important processes: Adiabatic process and Isothermal process. Adiabatic process is the process in which there is no exchange of heat from the system to its surroundings. There is no exchange of heat neither during compression nor during expansion.

Complete step-by-step answer:
During an adiabatic energy, there is no exchange of heat from the system to its surrounding neither during compression nor during expansion. Therefore, change in heat is equal to zero.
$\Rightarrow \Delta Q= 0$
$\Rightarrow Q= 0$ ...(1)
From the definition of entropy we know,
$\Delta S= \dfrac {\Delta Q}{T}$
From the above equation, it can be inferred that with change in heat, the entropy of the system also changes. So, using the equation. (1), we can say that as the change in heat is zero, change in entropy will also be zero.
$\Rightarrow \Delta S=0$... (2)
So, the correct answers are option A and C i.e. $\Delta S=0$ and Q=0 respectively.

So, the correct answers are “Option A and C”.

Note: In a real situation, building an adiabatic system is very difficult. Initially, the process can be adiabatic but due to some reversibility some heat is generated. Students generally get confused between adiabatic and isothermal processes. So, they must remember the difference between them. In an adiabatic process, the temperature changes with the amount of work done. While in an isothermal process, the temperature of the body is fixed constant throughout the process. In an adiabatic process, there is no heat transfer while in isothermal process heat transfer can be observed.