Thermal Expansion
Linear Expansion of Solids :
When a solid is subjected to a rise in temperature ?T , its increase in length ?L is very nearly proportional to its initial length L0 multiplied by
?L = ? L0 ?T
Where the proportionality constant ? is called the coefficient of expansion . The value of ? depends on the nature of the substance , for example , if a 1.000.000 cm length of brass becomes 1.000.019 cm long when the temperature is raised 1.0 0C , the linear expansion coefficient for brass is : -1 1.9x10-5 0 C = = 0.000.019 / 1.0 x 1 ?T L0 ?L / = ?
Area Expansion
If an area A0 expands to A0 + ?A when subjected to a temperature rise
?T , then :
?A = ? A0 ?T
Where : ? is the coefficient of area coefficient .
For isotropic solids ( those that expand the same way in all direction ), ? =2 ? approximately .
Volume Expansion :
If a volume V0 changes by an a mount ?V when subjected to a temperature change of ?T, then :
?V = ? V0 ?T
Where :
? : is the coefficient of volume expansion .
This can be either an increase or decrease in volume for isotropic solids :
? = 3 ? approximately .
Ideal gases :
Ideal gas: is one that obey the ideal gas law given below .At low to moderate ,pressures ,and at pressures not too low ,the following common gases can be considered ideal , Air , Nitrogen ,Oxgen , Helium, Hidrogen and an neon .
Ideal gas Law : The absolute pressure P of n kilo moles of gas contained in a volume V is related to the absolute temperature T by :
PV= nRT
Where : R = 8.314 J / Kmole and is called universal gas constant .
If the volume contains m kilograms of gas that has a molecular(or atomic)mass M .Then n = m /M .
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .