JEE Main · 2025 · 07 Apr 2025 · Shift 2 · Heat & Thermodynamics

In an isothermal process the temperature is fixed, so the internal energy does not change, $\Delta U=0$. In an adiabatic process no heat is exchanged, $Q=0$. In an isobaric process the gas expands or is compressed at constant pressure while its temperature changes, so $\Delta U\ne 0$. In an isochoric process the volume is fixed, so no work is done, $W=0$. Matching gives isothermal with $\Delta U=0$, adiabatic with $Q=0$, isobaric with $\Delta U\ne 0$, and isochoric with $W=0$.