Thermodynamics — Energy & Cycles

The first law — energy is conserved

ELI5: energy is never lost, only moved. Add heat Q to a gas and it either raises the internal energy U or does work W pushing a piston: ΔU = Q − W. That's the first law — a balance sheet that always balances.

Q_{in} := 500 J

= 500 J heat added

W_{out} := 200 J

= 200 J work the gas does on the piston

dU = Q_{in} - W_{out}

= 300 J internal energy rises by 300 J

✓ pass

abs(dU - 300 J) < 1e-9 J

heat in = work out + energy stored