Pressure vs Temperature
P/T = const at fixed V (Gay-Lussac).
Key Notes
Gay-Lussac's law: at constant volume, pressure × T = constant. P/T = const.
Equivalently: P₁/T₁ = P₂/T₂ for an ideal gas at constant V.
Direct proportionality between P and absolute T.
On P-T graph: straight line through origin (in Kelvin).
Extrapolating P to zero gives T = 0 K = absolute zero.
Microscopic: higher T ⇒ faster molecules ⇒ stronger wall collisions ⇒ higher P.
Pressure cookers use this: heating sealed container raises P, which raises boiling point ⇒ faster cooking.
Special case of ideal gas law at constant V and n.
Formulas
Gay-Lussac's law
P ∝ T at constant V.
Two-state form
Same gas, same V at two different T.
From ideal gas law
Linear in T at constant V, n.
Important Points
P-T law uses ABSOLUTE T (Kelvin) — NOT Celsius.
Doubling T (K) at constant V doubles P.
Aerosol cans warn against heating because P can rise enough to burst the can.
Tire pressure: rises as temperature rises (hot days, after driving).
Pressure cookers: heating raises P, which raises water's boiling point ⇒ food cooks faster.
Real gas deviations at low T (near phase change) and very high P.
Pressure vs Temperature notes from sciphylab (also known as SciPhy, SciPhy Lab, SciPhy Labs, Physics Lab). Class 11 physics revision for JEE Mains, JEE Advanced, NEET UG, AP Physics 1/2/C, SAT, and CUET-UG.