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Fundamentals of thermodynamics

  1. Thermodynamics Fundamentals of thermodynamics SD-Tech
  2. Prof. S. A. Dahake Point function and Path function A Point function (also known as state function) is a function whose value depends on the final and initial states of the thermodynamic process, irrespective of the path followed by the process. Example of point functions are density, enthalpy, internal energy, entropy etc. During the process if the value of variable depends on end states, they are known as point function. Al thermodynamics properties say pressure, volume, temperature are point function. Since a point function is only dependent on the initial or final state of the system but not on path follow SD-Tech
  3. Prof. S. A. Dahake Point function and Path function A Path function is a function whose value depends on the path followed by the thermodynamic process irrespective of the initial and final states of the process. It is clear from p-V diagram that, area under each curve represents work for each process For process A work done is b2A1a For process B work done is b2B1a For process C work done is b2C1a Since area under each curve is different, the amount of work obtain in each case will different and is not function of end state 1 or 2. Here magnitude of work depends on the path, hence work is path function. SD-Tech
  4. Prof. S. A. Dahake Quasi static process From the Latin quasi, meaning 'as if’ A quasi-static process is a thermodynamic process that happens slowly enough for the system to remain in internal thermodynamic equilibrium. An example of this is quasi-static expansion, where the volume of a system changes so slowly that the pressure remains uniform throughout the system at each instant of time during the process. If a process takes place at faster rate, then the intermediate condition can not be defined. Therefore, an assumption is made such that the process is taking place at a such rate that the intermediate condition can be defined and hence must be represented on a thermodynamic property diagram. SD-Tech
  5. Prof. S. A. Dahake Quasi static process Quasi = almost, Static = Constant SD-Tech
  6. Prof. S. A. Dahake Equilibrium A system is said to be in thermal equilibrium when temperature in all point in system is same. SD-Tech
  7. Prof. S. A. Dahake Temperature Temperature is a physical quantity that expresses hot and cold. There are three temperature scales in use today, Fahrenheit, Celsius and Kelvin. Fahrenheit temperature scale is a scale based on 32 for the freezing point of water and 212 for the boiling point of water, the interval between the two being divided into 180 parts. The 18th- century German physicist Daniel Gabriel Fahrenheit invent Fahrenheit scale. °C 100 = 𝐹−32 180 SD-Tech
  8. Prof. S. A. Dahake Temperature Celsius temperature scale also called centigrade temperature scale, is the scale based on 0 for the freezing point of water and 100 for the boiling point of water. Invented in 1742 by the Swedish astronomer Anders Celsius, it is sometimes called the centigrade scale because of the 100-degree interval between the defined points. K = 273+°C Kelvin temperature scale is the base unit of thermodynamic temperature measurement in the International System (SI) of measurement. It is defined as 1/ 273.16 of the triple point (equilibrium among the solid, liquid, and gaseous phases) of pure water. An absolute temperature scale named for the British physicist William Thomson, Baron Kelvin. SD-Tech
  9. Prof. S. A. Dahake Constant volume gas thermometer & Constant pressure gas thermometer A constant volume gas thermometer usually consists of a bulb filled with a fixed amount of a dilute gas which is attached to a mercury manometer. The manometer is used to measure variation in pressure. This thermometer works on the principle of Law of Gay-Lussac. The law states that when the temperature of an ideal gas increases, there is a corresponding increase in pressure. Also, when the temperature decreases, the pressure too decreases correspondingly. This is how constant volume gas thermometers traces the increase in temperature with the change in pressure while the volume remains constant. An apparatus of Constant pressure gas thermometer, based on Charles law in which a rigid vessel is filled with a gas, usually hydrogen or helium, at low pressure and its volume measured as its temperature is increased while its pressure is maintained constant. The device must be calibrated at two fixed points, such as the ice and steam points. SD-Tech
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