One mole of an ideal gas goes from an initial state A to final state B via two processes : It first undergoes isothermal expansion from volume V to 3V and then its volume is reduced from 3V to V at constant pressure. The correct P-V diagram representing the two processes is
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Answer
(4) [figure]
Solution
Isothermal expansion (V → 3V): PV = constant, so the path from A is a rectangular hyperbola going downward to the right; pressure falls to one-third.
Compression at constant pressure (3V → V): the path is a horizontal straight line from 3V back to V, directed to the left, ending at B below A.
Graph (4) shows a hyperbola from A followed by a horizontal line back to B.
Answer: (4)