Download Laws of Thermodynamics - Lecture Slides | MTLE 6030 and more Study notes Thermodynamics in PDF only on Docsity! Lecture 1 Laws of Thermodynamics Thermodynamic state - equilibrium Thermodynamic processes Laws of thermodynamics Absolute Temperature Problems 2.5, 2.6, 2.8 Thermodynamic intensive coordinates are uniform across the whole system (T, P, ) or across each macroscopic phase (e.g., water and ice density density at the melting point. All thermodynamic coordinates are time independent Mechanical equilibrium, thermal equilibrium and chemical equilibrium Thermodynamic state - equilibrium Two or more systems in equilibrium do not exhibit heat flow among each other, they are at the same temperature Later we will see that criterion of equilibrium for isolated system, i.e., const E, V, T is the maximum entropy state dS(E, V, N) = 0 0th law of thermodynamics E1, V1, N1 E2, V2, N2 dS = dS1+dS2 = 0 dS1 S1 E1 dE1 S1 V1 dV1 S1 N1 dN1 S1 E1 dE1 Allowing only energy exchange between two isolated systems dS2 S2 E21 dE2 S2 V2 dV2 S2 N2 dN2 S2 E2 dE2 dS1 dS2 S1 E1 dE1 S2 E2 dE1 dE2 dE1 From conservation of energy S1 E1 S2 E2 T E S 1st law of thermodynamics - conservation of energy dE = dQ-dW d indicates inexact differential - depends on the integration path In a cycle, E = 0 net Q in = net W out Work and heat are not state functions Energy is a state function dW = Fdx can be PdV, -dl, -it 2nd law of thermodynamics - entropy For a reversible process dQ= TdS Where S is entropy which a state function, and T is an absolute temperature The entropy can by calculated by integrating heat over a reversible path S f Si dQ TR Problem 2.6 A vessel of volume VB contains n moles of gas at high pressure. Connected to the vessel is a capillary tube trough which the gas may slowly leak out into the atmosphere, where P=P0. Surrounding the vessel and capillary is a water bath, in which is immersed an electric resistor. The gas is allowed to leak slowly trough the capillary into the atmosphere while, at the same time, electrical energy is dissipated in the resistor at such a rate that the temperature of the gas, the vessel, the capillary and the water is kept equal to that of the surrounding air. Show that, after as much gas is leaked as is possible during time , the change of internal energy is where, v0 = molar volume of gas at P=P0, = potential on the resistor, and i is the current. E i P0(nv0 VB ) Problem 2.8 The tension in a wire is increased quasi statically and isothermally from 1 to 2. If the length, cross-sectional area and isothermal Young’s modulus (Y) remain practically constant, show that the work done by the wire is: W L 2AY ( 2 2 1 2)
