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Temperature,Heat And 1st Lw Of Thermodynamics

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This ppt was covered the temperature unit, different between the temperature and heat, what is the heat, what is the thermal absorption, what is the 1st law of the thermodynamics,etc.

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    Chapter 1 Thermodynamics Temperature, Heat, and the First Law of Thermodynamics By SANTHAKUMAR S
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    182 Temperature What is 'temperature' ? Feeling of hot and cold To be defined, measured with other properties of a system A state variable of a system 'Z 108 106 104 102 100 Universe just after beginning Highest laboratory temperature center Of the Sun Surface of the Sun Tungsten melts 'Water freezes Universe today Boiling helium-3 Record IOW temperature 10—9 Fig. 1 8-1 Some temperatures on the Kelvin scale. Temperature T 0 corresponds to 10-u and cannot be plotted on this logarithmic scale.
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    18.3: The Zeroth Law of Thermodynamics If bodies A and B are each in thermal equilibrium with a third body T, then A and B are in thermal equilibrium with each other. # Thermal equilibrium: The temperature is constant in time. Flgu 18-3 (a) Body T (a thermoscope) and body A are in thermal equilibrium. (Body S .is a thermally insulating screen.) (b) Body Tand body B are also in thermal equilibrium, at the same reading of the thermoscope. (c) If (a) and (b) are true, the zeroth law of thermodynamics states that body .A and body B are also in thermal equilibrium.
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    18.4 Measuring Temperature 273.16 K Gas thermometer bulb Vapor (triple-point temperature), The Kelvin scale, the absolute temperature scale Ice IVater Fig. 18-4 A triple-point cell, in which solid ice, liquid water, and water vapor co- exist in thermal equilibrium. By interna- tional agreement, the temperature of this mixture has been defined to be 273.16 K. Ihe bulb of a constant-volume gas ther- mometer is shown inserted into the well of the cell.
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    18.4 The Celsius and Fahrenheit Scales T -T 273.150 Triple point of water T 5 Tc + 320, Absolute zero 273.16K OK o.orc 32.020F -273.150c -459.670F Fig. 18-7 The Kelvin, Celsius, and Fahrenheit temperature scales compared.
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    18.4 Measuring Temperature, The Constant Volume Gas Thermometer The temperature of a body can be T=cp defined as where p is the pressure in the bulb. Assuming at the triple point, we also have TB CP3, with the same constant C. Therefore, (273.16 K) But only when the gas is of a very small amount, this measurement gives consistent results among different materials used. T- (273.16K) lim gas—O P 3 This is called the 'ideal gas temperature'. Scale Gas-filled bulb P PO — pgh Fig. 18-5 A constant-volume gas ther- mometer, its bulb immersed in a liquid whose temperature Tis to be measured.
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    18.6: Thermal Expansion, Linear Expansion If the temperature of a metal rod of length L is raised by an amount AT, its length is found to increase by an amount in which u is a constant called the coefficient of linear expansion. Table 18-2 Some Coefficients of Linear Expansiona Substance Ice (at OOC) Lead Aluminum Brass Copper Concrete a(10 6/ca) 51 29 23 19 17 12 Substance Steel Glass (ordinary) Glass (Pyrex) Diamond b Invar Fused quartz a (10 6/C0) 11 9 3.2 1.2 0.7 0.5 "Room temperature values except for the listing for ice. blhis alloy was designed to have a low coefficient of expansion. The word is a shortened form of "invariable."
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    18.6: Thermal Expansion, Volume Expansion AV VßAT ß is the coefficient of volume expansion. The coefficients of volume expansion and linear expansion are related by 13 3a. 1+3 1 1 2 2 3 3 4 4 5 Circle 5 6 7 Circular hole 06 07 Fig. 18-11 Tie same steel ruler at two dif- ferent temperatures. When it expands, the scale, the numbers, 'the thickness, and the di- ameters of the circle and circular hole are all increased by the same factor. (The expansion has been exaggerated for clarity.)
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    18.7: Temperature and Heat Heat is the energy transferred between a system and its environment because of a temperature difference that exists between them. Fig. 18-12 If the temperature of a system exceeds that of its environment as in (a), heat Q is lost by the system to the environment until thermal equilibrium (b) is established. (c) If the temperature of the system is below that of the environment, heat is absorbed by the system until thermal equilibrium is established. The system has a higher temperature, so Environment System Ts>TE Environment The system has the same temperature, so s System The system has a lower temperaturet so (c) Environment System Ts
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    187: Temperature and Heat: Units •The calorie (cal) was defined as the amount of heat that would raise the temperature of 1 g of water from 14.50C to 15.50C. •In the British system, the corresponding unit of heat was the British thermal unit (Btu), defined as the amount of heat that would raise the temperature of 1 1b of water from 630F to 640F. •The SI unit for heat is the joule. •The calorie is now defined to be 4.1868 J. •1 cal =3.968 x 10-3 Btu = 4.1868 J.
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    18.8: The Absorption of Heat + The heat capacity C of an object is the proportionality constant between the heat Q that the object absorbs or loses and the resulting temperature change AT of the object Q CAT c(Tf TX) in which Ti and T are the initial and final temperatures of the object. + Heat capacity C has the unit of energy per degree or energy per kelvin.
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    18.8: The Absorption of Heat: Specific Heat The specific heat, c, is the heat capacity per unit mass. It refers not to an object but to a unit mass of the material of which the object is made. When specific heats are expressed in units of moles (rather than a mass unit), they are called molar specific heats, I mol = 6.02 X 1023 elementary units # It is important to distinguish the heat transfer is done with constant volume or constant pressure. The specific heat is different for different processes, particular for gases. Table 18-3 Some Specific Heats and Molar Specific Heats at Room Temperature Specific Heat Substance Elemental Solids Lead Tungsten Silver Copper Aluminum Other Solids Brass Granite Glass Ice (-100c) Liquids Mercury Ethyl alcohol Seawater Water cal 0.0305 0.0321 0.0564 0.0923 0.215 0.092 0.19 0.20 0.530 0.033 0.58 0.93 1.00 Molar Specific Heat mol K 26.5 24.8 25.5 24.5 128 134 236 386 900 380 790 840 2220 140 2430 3900 4187
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    18.9: dW A Closer Look at Heat and Work ds (pA)(ds) — ds) Gas moves from i to f, doing positive work. Process Volume We can control how much work it does. Volume (b) It still goes from i to f, but now it does more work. Volume Moving from f to it it does negative work. Volume Lead shot •steam • (c) 0 0 It still goes from i to f but now it does less work. Volume Cycling -clockwise yields a positive net work. Volume 35.4)/ 0 0 0 0 Thermal resen'0ir Insulation Control knob Fig. 1 8-17
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    18.10: The First Law of Thermodynamics Tie internal energy Eint of a system tends to increase if energy is added as heat Q and tends to decrease if energy is lost as work W done by the system. law). (Q is the heat absorbed and W is the work done by the system). V The quantity (Q W) is the same for all processes. It depends only on the initial and final states of the system and does not depend at all on how the system gets from one to the other. V This is simply conservation of energy.
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    18.11: Some Specific Cases of the First Law of Thermodynamics 1. 2. 1. 2. Adiabatic processes. An adiabatic process is one that occurs so rapidly or occurs in a system that is so well insulated that no transfer of thermal energy occurs between the system and its environment. Putting Q=O in the first law, AEint W (adiabatic process) Constant-volume processes. If the volume of a system (such as a gas) is held constant, so that system can do no work. Putting W=O in the first law, constant-volume process) Cyclical pro after certain AAA interchanges of heat and work, the system is restored to its initial state. No intrinsic property of the system including its internal energy can possibly change. Putting Eint = 0 in the first law Free expansion: (cyclical process) which no heat transfer occurs between the system and its environment and no work is done on or by the system. Thus, Q =W =0, and the first law requires that o (free expansion)
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    18.11: Some Specific Cases of the First Law of Thermodynamics Table 18-5 The First Law of Thermodynamics: Four Special Cases The Law: = Q - w (Eq. 18-26) Process Adiabatic Constant volume Closed cycle Free expansion Restriction Q w o w Consequence AEint AEint
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    18.12: Heat Transfer Mechanisms: Conduction We assume a steady transfer of energy as heat. Cold reservoir Hot reservoir TH>Tc Fig. 18-18 Thermal conduction. Energy is transferred as heat 'from a reservoir at temperature TH to a cooler reservoir at temperature Tc 'through a conducting slab of thickness L and thermal conductivity k A slab of face area A and thickness L, have faces maintained at temperatures TH and T by a hot reservoir and a cold reservoir. If Q be the energy that is transferred as heat through the slab, from its hot face to its cold face, in time t, then the conduction rate Pc (the amount of energy transferred per unit time) is cond Here k, called the thermal conductivity, is a constant that depends on the material of which the slab is made. The thermal resistance R of a slab of thickness L is defined as:


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