PHYSICS CHAPTER 11 & 12

• Thermodynamics


  The study of the relations between heat, work, temperature, and energy
• First law of thermodynamics

  The change in internal energy of a system is equal to the heat added to the system minus the work done by the system
• Joule's mechanical equivalent of heat

  The amount of work required to produce 1 calorie of heat
• Calorie


  The energy that would be required to raise one gram of water by one degree Celsius
• Calorie (capital C)


  The unit used on food labels
• Calorific value


  The amount of heat energy present in food or fuel and which is determined by the complete combustion of specified quantity at constant pressure and in normal conditions
• Heat of combustion


  The amount of heat liberated when a given amount of the substance undergoes combustion
• Heating value


  The amount of heat released during the combustion of a specified amount of a substance
• Mercury thermometer


  • Uses mercury as the thermometric liquid, mercury has a higher freezing point compared to alcohol
• Alcohol thermometer


  • Uses alcohol as the thermometric liquid
• Thermocouple


  A sensor used to measure temperature, consisting of two wire legs made from different metals welded together at one end
• RTD (Resistance Temperature Detector)


  Uses the property that the resistance of a conductor changes with temperature
• Thermistor


  A type of resistor whose resistance varies significantly with temperature
• Latent heat


  The heat or energy that is absorbed or released during a phase change of a substance
• Expansion


  An increase in size of an object when heat is applied
• Bimetallic strip


  Used to convert a temperature change into mechanical displacement, consisting of two strips of different metals which expand at different rates when heated
• Heat


  A measure of the total energy of molecular motion
• Latent heat of fusion (Lf)


  The heat supplied to cause a substance to change from the solid state to the liquid state
• Latent heat of vaporization (Lv)


  The heat required to change a substance from the liquid state to the gaseous state
• Conduction


  Heat transfer from one molecule to nearby molecules
• Convection


  Heat transfer by movement of fluids (gases or liquids)
• Radiation


  Heat transfer by electromagnetic radiation
• Greenhouse effect


  Radiant heat energy entering a closed building or vehicle is reflected, causing the interior to become much warmer than the outside
• Kinetic-molecular theory of gases


  Assumes ideal gas molecules are constantly moving, have negligible volume and intermolecular forces, undergo perfectly elastic collisions, and have average kinetic energy proportional to absolute temperature
• Adiabatic process


  No heat transfer, ΔU = -W
• Isothermal process


  Constant temperature, ΔU = 0, Q = W
• Isobaric process


  Constant pressure, ΔU, W, and Q are generally non-zero, W = P·ΔV
• Isochoric process


  Constant volume, W = 0, ΔU = Q
• Thermodynamic cycle


  A closed system that undergoes various changes in temperature, pressure, and volume, with the final and initial states being equal
• Power cycles


  Cycles that convert heat input into mechanical work output
• Heat pump cycles


  Cycles that transfer heat from low to high temperatures using mechanical work as input
• Carnot cycle


  An ideal reversible closed thermodynamic cycle with isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression
• Diesel cycle


  An ideal-engine cycle with adiabatic compression, constant-pressure heating, adiabatic expansion, and constant-volume cooling
• Otto cycle


  An ideal thermodynamic combustion cycle with compression at constant entropy, constant-volume heat transfer, expansion at constant entropy, and constant-volume heat transfer
• Brayton cycle


  The thermodynamic cycle used in jet engines, involving an isobaric process in the combustor and isentropic processes
• Aerospace engineers rely on thermodynamics to understand and optimize the performance of propulsion systems, as the efficiency depends on effective conversion of fuel potential energy into kinetic energy