Thermal Physics Flashcards
Thermal expansion coefficient
B = 1/V*dV/dT = d(lnV)/dT
Fourier’s heat conduction law
Rate of heat flow = q(dot) = -kA*dt/dx
k is thermal conductivity.
Virial Equations of State
PV = nRT(1+B/(V/n) + C/(V/n)^2)
Approximation of e^-x for small x
e^-x = 1-x for small x
Van der Waals equation
P=nRT/(V-nb)-a(n/v)^2
Equipartition theorem
At temperature T, the average energy of any quadratic degree of freedom is kT/2.
Total thermal energy
U = NfkT/2
First law
deltaU = q+w
Adiabatic process
No heat transfer between system and surroundings. q=0.
Isothermal
deltaU = 0
Max work
Available when change takes place reversibly
Isothermal + reversible
deltaU = 0, q = -w = nRT*ln(Vf/Vi)
heat capacities
c(v) = q(v)/deltaT = deltaU/deltaT, c(p)=q(p)/deltaT
Work in terms of heat capacity
w=nc(v)deltaT
work + means work done on the gas, compression, T of gas increases
work - means work done by the gas, expansion, T of gas decreases
Latent Heat
q = mL
Enthalpy
H = U+PV
Virial Theorem
In any system where particles are held together by mutual gravitational attraction: U(potential) = -2U(kinetic)
Adiabatic expansion/compression of ideal gas
PV^gamma = constant gamma = (f+2)/f = c(p)/c(v) c(p) = c(v)+R
Mechanical equilibrium
Net force = 0
Temperature
A measure of how easily the multiplicity of the system changes with energy
Stirling’s approximation
ln(N!) = NlnN - N
Approximation of ln(1+x) for small x
ln(1+x) = x for small x
Second law
Any large system in equilibrium will be found in the macrostate with greatest entropy
Boltzmann’s equation
S = kln(multiplicity) in J/K