Basic Physics Lecture 2 PDF

Basic Physics OFRPY102 Lecture 2 Prepared by: Associate Professor Dr. Yahia Elbashar and Dr. Yasser Nada Dr. Yahia Elbashar 1 Heat & Temperat ure Heat: The amount of energy transferred from one body to another...

Basic Physics OFRPY102 Lecture 2 Prepared by: Associate Professor Dr. Yahia Elbashar and Dr. Yasser Nada Dr. Yahia Elbashar 1 Heat & Temperat ure Heat: The amount of energy transferred from one body to another by virtue of a temperature difference between them. Heat is not the energy content of a body although it is frequently used that way. The proper term is thermal energy. Unit of heat is: Joule Temperature: A measure of the average kinetic energy of the molecules of a substance. That property of a body of matter that gives rise to sensations of hot and cold. Temperature and Thermal Energy Temperature - measure of the average kinetic energy of the particles in a substance - particles in box on right have higher temperature - higher velocity = more KE = higher temperature  TEMPERATURE SCALES CONVERSIONS: CELSIUS TO KELVIN K = C + 273. CELSIUS TO FAHRENHEIT F = 9/5C + 32 FAHRENHEIT TO CELSIUS C = 5/9 x (F - 32)  Physical base of thermometer Regular physical change with temperature For example : In Mercury thermometer : the mercury expands regularly with temperature increase.  Heat units Calorie or Joule 1 calorie = Amount of thermal energy required to change the temperature of 1 gram of water 1°C. (1 Calorie = 4.187 joules) 1 kilocalorie = 1,000 calories  Specific Heat  Specific Heat is the quantity of heat required to change the temperature of 1 gram of a substance by 1° C. . Water has high specific heat capacity - used as a cooling fluid.  Specific heat capacity of water is 1 (calorie / gram-deg. C). Calculation of absorbed or released heat For m grams of a substance, Q = c m ∆T  Heat Transfer Processes  Conduction – transfer of heat from a region of higher temperature to a region of lower temperature by increased kinetic energy moving from molecule to molecule through collisions between molecules. Occurs in solids.  Convection – transfer of heat from a region of higher temperature to a region of lower temperature by the flow of higher energy molecules. Occurs in gases and liquids.  Radiation – transfer of heat by emission and absorption of radiant energy (energy that can travel through space as electromagnetic radiation, like visible light). Conduction Convection Radiation  temperatu re 100oC Water+ vapor ice+ 0oC water Time  Phase/State Changes Heat transfer always occurs whenever a substance chang Melting - when a solid changes to a liquid Energy is Evaporation - when a liquid changes to a gas absorbed Sublimation - when a solid changes directly t Condensation - when a gas changes to a liqui Energy is released Freezing - when a liquid changes to a solid Latent heat ‫الحرارة‬ ‫الكامنة‬ The amount of heat required to change the matter form one state to another without change in its temperature Latent heat of fusion The amount of heat required to change the matter form solid state to liquid without change in its temperature Latent heat of Vaporization The amount of heat required to change the matter form liquid state to gas without change in its  Thermodynamics definition Thermodynamics is the study of the inter-relation between heat, work and internal energy of a system and its interaction with its environment. System Laws of thermodynam ics First law of thermodynamic U =  Types of process according to the first law of thermodynamic Adiabatic Isothermal Heat transfere NO heat Constant transferred temperature of the system Isobaric Isochoric Constant Constant volume pressure Adiabatic Process An adiabatic process transfers no heat therefore Q = 0 ΔU = Q – W When a system expands adiabatically, W is positive (the system does work) so ΔU is negative. When a system compresses adiabatically, W is negative (work is done on the system) so ΔU is positive.  Isothermal Process An isothermal process is a constant temperature process. Any heat flow into or out of the system must be slow enough to maintain thermal equilibrium For ideal gases, if ΔT is zero, ΔU = 0 Therefore, Q = W Any energy entering the system (Q) must leave as work (W) Isobaric Process An isobaric process is a constant pressure process. ΔU, W, and Q are generally non-zero, but calculating the work done by an ideal gas is straightforward W = P·ΔV Water boiling in a saucepan is an example of an isobar process Isochoric Process An isochoric process is a constant volume process. When the volume of a system doesn’t change, it will do no work on its surroundings. W = 0 ΔU = Q Heating gas in a closed container is an isochoric process  Second law of thermodynam ics  Heat ‫خريطة‬ ‫المفاهيم‬ temperature Specific heat Latent heat & Phase change Thermodynami c Zeroth law Second law First law