1 / 2

Subjects to be discussed: Defn T: Av KE KE directly proportional to absolute T, KE---kT

Subjects to be discussed: Defn T: Av KE KE directly proportional to absolute T, KE---kT 0th Law: A↔C & B↔C Then A↔B Heat: energy transfer due delta T U: total internal E: sum of all KE+PE Heat conduction Δ Q/ Δ t = kA ( Δ T/ Δ x)--- k:thermal conductivity, (..) thermal gradient

aysha
Download Presentation

Subjects to be discussed: Defn T: Av KE KE directly proportional to absolute T, KE---kT

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Subjects to be discussed: • Defn T: Av KE • KE directly proportional to absolute T, KE---kT • 0th Law: A↔C & B↔C Then A↔B • Heat: energy transfer due delta T • U: total internal E: sum of all KE+PE • Heat conduction ΔQ/Δt = kA (ΔT/Δx)--- k:thermal conductivity, (..) thermal gradient • convection: heat flow in a fluid medium • radiation: no medium needed for propagation, elctromagnetic radiation, P~ AT4 • Specific Heat Capacity: heat needed to raise T of 1 kg of a substance by 1 Cº. • assume C is indep of T. Is it? (J kg-1 K-1) • Thermal Equilibrium: reached at T1=T2 • Specific Latent Heat of Fusion: heat required to melt a unit mass of A at its (normal) melting point • Q= m L • Phase changes • Idael Gases: no V (point newtonian particles), no interaction (zero intermolec forces), • elastic collisions, vacuum between particles • ½ mv2 = 3/2 kT v2= (v12 + v22 + v32 +...)N or RMS speed ~ average speed (but actually • not the same but close). Average velocity = 0 • Total Internal E of Ideal gas (U) depends ony on T or KE since no PE • U = 3/2 N kT (total int E for N ideal gas atoms) • P ~ (speed of molec x collisions with walls) molecular defn • P= F/A (macroscopic defn) • Boyle Mariotte Law: P ~ 1/V at n,T const. PV=const, V= const/P • Charles Law V ~ T at const P,n V = const x T • Avogadro’s Law: V ~ n at const T, P. V= const X n • V= const/P = const x T = const x n → V ~ nT/P.... V= nRT/P... PV=nRT Equation of state

  2. U =3/2 NkT = 3/2 nRT= 3/2 PV for point-monoatomic particles. if polyatomic U is bigger • Mechanical work done by gas: w= PΔV (area under PV curve at const n, T) • work done by the sys (negative sign, internal E decreases), work done on the sys positive • Isobaric: const P, isochoric: const V, isothermal: const T, adiabatic: ΔQ=0 • 1st LAW: ΔU= q + w U: state function-capital letters, q and w are not—lower case • SOLVE EXAMPLE FROM PETRUCCI, isothermal +adiabatic expansion: waht happens to T, w, q • and U ? • 2nd LAW: in a heat engine, absorbed heat can not be completely converted into work. • (no %100 ordered flow of energy) • or: in a spontaneous process: ΔSunverse>0 • ΔS= ΔQ/T • Heat does not flow from cold to hot objects • Effiicieny of a Heat Engine Eff= W/Qh= (Qh – Qc)/ Qh< 1 • The most efficient engine: Carnot Heat engine Eff= (Th-Tc)/Th

More Related