The pressure-volume curve for a fixed temperature is called

Correct option is B

Correct Answer: (b) Isotherm
Explanation:
· A pressure–volume (P–V) curve at a fixed temperature is called an isotherm.
· “Iso” means same, and “therm” means temperature → so an isotherm represents all states of a gas at constant temperature.
Information Booster:
· Isotherms are used in Boyle’s Law, which states:
· P ∝ 1/V (at constant temperature)
· On a P–V graph, isotherms are downward-sloping curves (hyperbolic).
Additional Knowledge:
· Isobar (a): Constant pressure curve (P = constant).
· Isochors (c): Constant volume curve (V = constant).
· Isotope (d): Atoms of the same element with different mass numbers; unrelated to P–V curves.