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# MU PHY 182 - Energy and Work in Fluids

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PHY 182 1st Edition Lecture 3Outline of Last Lecture I. Definition of an Ideal GasII. Measuring Temperature & Introduction to ThermodynamicsIII. Applying the Ideal Gas LawOutline of Current Lecture I. How Energy is TransferredII. Work in Ideal-Gas ProcessesCurrent LectureHow Energy is Transferred- Be sure to remember important energy equations such as K=Wc+Wdiss+Wext Wc:work done by conservative forces (i.e. change in gravitational energy) Wdiss: work done by dissipative forces (i.e. friction) Wext: work done by external forces- The total energy of an isolated system in constant.- Heat (Q) is defined as the energy transferred in a thermal interaction, it is not a quality of an object or substance.- In thermodynamics, work is always external work.- A mechanical interaction is one in which the system and environment interact via microscopic pushes and pulls.- Mechanical equilibrium is reached when there is zero net force on the system.- Heat is path-dependent, just like work.- Heat is transferred between 2 objects as a result of temperature difference.- The unit we will use for heat is joules (this shows an obvious relationship between heat and energy that will be explained more thoroughly later on).Work in Ideal-Gas Processes- Positive work: force causes object to speed up; system's energy increases- Negative work: force causes object to slow down; system's energy decreases- Keep in mind that work is not a state variable.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Work done on a gas is equal to the negative integral of its pressure with respect to volume, evaluate from initial volume to final volume. You can also say that work is equal to the area under the PV curve multiplied by -1.- An isochoric process is one in which the volume of the gas is held constant. The work done during an isochoric process is 0.- An isobaric process is one in which the pressure of the gas is held constant. The work done during an isobaric process is equal to -P V.Δ- An isothermal process is one in which the temperature of the gas is held constant. The work done during an isothermal process is (-nRT)(ln |Vf/Vi|)- The work done during an ideal-gas process depends on the path followed through the PV diagram.- If there is a gas in a sealed container that contains a piston, the work done is positive if the gas is compressed and negative if the gas

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