engineering Flashcards
conservation of angular momentum
If no external unbalanced torques act then the angular momentum of a system of bodies is conserved.
second law of thermodynamics
It is not possible for a heat engine working in a cycle to absorb thermal energy and convert it all to work (Kelvin–Planck).
Enthropy (S)
a measure of the disorder in a system (the number of ways that energy can be shared).
U = 3/2RT is only true for
monatomic gases such as neon, helium and argon
simple version first law thermodynamics
if a gas expands and gets hot, heat must have been added
adiabatic process
when there is no exchange of heat between the system and the surroundings
net work done
difference between the work done by the gas and the work done on the gas
equation for first law thermodynamics
Q = change in internal energy + work done
2 ways to get an adiabatic process
1) system thermally insulated from environment
2) move piston really fast so no time for heat flow
clausius statement
heat will not spontaneously flow from cold to hot
kelvin planck statement
a heat engine cannot convert all of the heat energy it extracts into useful work
reversible process
when the gas can be returned to its original state without any change to the environment - eg. an adiabatic process where no heat is transferred
There can be no change in enthropy in an adiabatic process
isochoric temp rise thermodynamic implications
no work done so heat added increases the temperature
isobaric expansion thermodynamic implications
gas does work and gets hot so heat must be added.
isothermal expansion implications
gas does work but no change in temperature heat must be added.
