Question

What is the first law of thermodynamics and how is it related to conservation of energy?

Answer 1

It is basically the conservation of energy transferred from heat flow and work within a closed system (our universe counts, because we can hardly reach the "edge" of the universe).

The first law of thermodynamics can be defined as:
`DeltaU` = `q + w` = `Delta(TS)` - `Delta(PV)` = `TDelta(S)` - `PDelta(V)`

...at a constant temperature and pressure, where U is internal energy, q is heat flow (J), w is work (J), S is entropy (J/K), T is temperature (K), P is pressure, and V is volume (L) (You see this in late college physics for sure, when you work with engines and Carnot cycles).

or the differential form:
`dU = deltaq + deltaw` = `TdS` - `PdV`

...where `d` refers to full differentials and `delta` refers to partial differentials. You might see this in late Physical Chemistry.

or the simpler form:
`DeltaU` = `K` or `DeltaPE` = `DeltaKE`
You might see this in early college Physics.