Abhyaas Series Ep 11 | JEE Advanced 2026 | Physics Paper 1 Q11

Episode 11 of the Abhyaas Series is here. Two sections of gas are separated by a thermally conducting but fixed partition on one side and a freely moving but insulating piston on the other. Heat flows through the conducting partition and the movable piston adjusts to keep section S2 always at atmospheric pressure. You have to find the value of n in the time expression for the temperature difference to halve. This question is a genuine crossover between thermal conduction and thermodynamics and it is one of the most demanding question types JEE sets. The rate of heat conduction through the partition depends on the temperature difference at that instant. But as heat flows into S2, the piston moves and S2 does work on the atmosphere. That means not all the heat entering S2 goes into raising its temperature. You have to account for this correctly to set up the right differential equation. Once the differential equation is set up the math is clean. It is an exponential decay of the temperature difference and finding when it halves brings in ln 2, which the question conveniently gives you as 0.7. What we cover in this video :- Understanding the role of each partition: P1 conducts heat, P2 maintains constant pressure in S2 Writing the rate of heat flow through P1 using Fourier's law of conduction Setting up the energy balance for S2 accounting for heat input and work done by the piston Why S1 is at constant volume and how its temperature change relates to heat lost Combining both energy equations to get a differential equation for the temperature difference Solving the differential equation and finding the time for the difference to become half of the initial value Extracting the value of n Concept used: Thermal Conduction, Thermodynamics, First Law of Thermodynamics, Differential Equations in Physics Source: JEE Advanced 2026 | Physics Paper 1 | Q11 If this helped, share it with your JEE prep group. Subscribe for the full Abhyaas Series covering every JEE Advanced 2026 Physics question one by one.