$)$

b$)$ Water initially at pressure $P_1$ and temperature $T_1$ is contained in a freely moving piston$-$

cylinder device fitted with stops as shown in Figure Q$1-1.$ The water is cooled in Process A

during which the piston moves from Position $1$ to Position $2$ where the piston rests on the

stops at the end of the process. Then, the system undergoes further cooling in Process B till

the pressure reduces to half of the initial pressure at the end of Process B$.$

i$)$ What type of process involved during Process A and B$?$

ii$)$ Define an isobaric process in a sentence.