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21 thermodynamics
 

21 thermodynamics

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    21 thermodynamics 21 thermodynamics Presentation Transcript

    • Heat and Temperature THERMODYNAMICS
    • HEAT  HEAT is energy (thermal) in transit, energy that transfers from one body to another because of temperature difference.  Heat flows from an area of high temperature to an area of low temperature (unless an external work is done).  Heat is measured with the following SI units: joules (J); calorie (cal); kilocalorie (kcal or Cal) where: 1 cal = 4.184J and 1 Cal = 1000cal
    • SOURCES OF HEAT A. NATURAL SOURCES 1. the Sun 2. interior of the Earth B. ARTIFICIAL SOURCES 1. chemical action 2. mechanical energy 3. electrical energy 4. nuclear energy
    • THERMAL ENERGY AND TEMPERATURE THERMAL ENERGY - also called Internal Energy - the total energy in a system or body; the sum of kinetic and potential energy of the atoms or molecules of a body TEMPERATURE - measure of the degree of hotness or coldness of a body - the average kinetic energy of the molecules of a body
    • Touching - Very easy to use - However, it is unreliable and has limitations
    • *Liquid-in-glass *thermocouple *Rotary *Liquid crystal thermometer
    • - A liquid inside a glass tube expands and contracts with a change in temperature
    • - Uses circuits to measure changes in electric current due to changes in temperature
    • - Uses a coiled bimetallic strip
    • - Uses a strip of liquid crystals that changes color with temperature
    • *Fahrenheit, F *Celsius, C *Kelvin, K
    • METHODS OF HEAT TRANSFER 1. CONDUCTION – heat transfer through solids *Thermal conductivity – ability of a material to allow heat to pass through * Kinds of material based on thermal conductivity: a. conductors – allow heat to pass through b. insulators – resist heat transfer 2. CONVECTION – heat transfer through fluids (liquids and gases), which involves currents/flow 3. RADIATION – heat transfer through empty space, through electromagnetic radiation, such as light, microwave, etc.
    • HEAT TRANSFER