What does “First law of thermodynamics” actually mean in Thermodynamics & Kinetic Theory, and why does it matter for JEE?
energy conservation for gases: ΔU = Q − W, where W is work done BY the gas.
In simple words: energy conservation for gases: ΔU = Q − W, where W is work done BY the gas. Getting First law of thermodynamics clear matters because JEE questions on Thermodynamics & Kinetic Theory usually test this idea directly, not just a formula you memorised.
Key point
First law of thermodynamics
Common mistake
getting the sign of W wrong (work done by vs on the gas).
Memory tip
heat in is +Q; work done by the gas is +W and lowers ΔU.
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