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This course on thermodynamics explores fundamental concepts such as thermal energy, internal energy, temperature, heat, and power. Key principles include the Ideal Gas Law, heat transfer dynamics, and thermal expansion. We delve into kinetic theory, explaining molecular motion and interactions, and discuss the First Law of Thermodynamics, which relates to energy conservation. Additionally, we examine PV diagrams, heat engines, and the Second Law of Thermodynamics, emphasizing entropy and energy transformations in physical systems.
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Ch 18: Thermodynamics AP Physics B Summer Course 20122012年AP物理B暑假班 M Sittig
Heat, Temperature and Power • Thermal energy: (Etherm) • Internal energy: The sum of all energies of all molecules in a substance (U). • Temperature: Related to the average kinetic energy per molecule in a substance (T). • Heat: Thermal energy (Q). • Power: Work per time, rate of use of energy (P).
Rate of Heat Transfer • H=k·A·ΔT/L (= Q/t) • Directly proportional to • Thermal conductivity (k) • Area • Temperature Difference. • Inversely proportional to • Length • Think of it like water flowing through a pipe.
Thermal Expansion • Heat makes molecules vibrate more, move apart. • Materials expand, holes in material expand.
Ideal Gas Law • Just remember from Chemistry: • PV = nRT • Where n is moles. • Also in the form: • PV = NkBT • Where N is molecules.
Ideal Gas Law • Remember that the ideal gas law summarizes the three smaller gas laws: • Boyle’s Law: V ~ 1/P • Charle’s Law: V ~ T • Pressure Law: P ~ T • But you don’t have to memorize these, just remember the Ideal Gas Law.
Kinetic Theory of Gases • Molecules move in continuous, ____ motion. • There are a _____ number of molecules in any container of gas. • The _____ between gas molecules is large. • Molecules do not act on one another at a ____. • All collisions between molecules, and of molecules on container walls, are _____.
Kinetic Theory of Gases • U = (3/2) nRT: most important thing is that internal energy (U) is directly proportional to (T), and only T. • vrms = sqrt( 3kBT/m ): most important thing is that T is related to KE, so you need a square root and the mass of a molecule to find v.
First Law of Thermodynamics • Comes from the conservation of energy, so think about what flows in and out. • ΔU = change in internal energy of a sample of gas. • It can be positive (U increasing) if: • Q = heat flows into the gas • W = work is done on the gas • If heat flows out or work is done by the gas, the value of Q or W is negative and U decreases.
