P152 Fall 2017 Exam1 Review.pdf - Physics 152 Fall 2017 SI...

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Physics 152 Fall 2017 SI Leader: Hubert Lin Tues. 7:00-9:00PM SI Exam 1 Review Packet ILC S131 Thermal Expansion – stuff expands when heated Two types: linear and volume thermal expansion Formulas Linear thermal expansion Δ𝐿 = 𝛼𝐿 Δ𝑇 𝛼 = coefficient of linear expansion Volume thermal expansion Δ𝑉 = 𝛽𝑉 Δ𝑇 𝛽 = 3𝛼 = volume coefficient of expansion Class Questions Compare the linear/volume expansion of 2 different objects Ex. Two spheres of different volumes (same material & initial temp) are heated to the same temperature. When one sphere reaches x volume, what is the volume of the other sphere? How much greater is the expansion of one compared to the other etc. Analyzing changes in length/volume Ex. A cube is heated and it’s length increases by x. What does its volume increase by? Ideal Gas Law – it’s the ideal gas law Two versions: macroscopic and molecular Pressure – force/area Absolute pressure = pressure relative to pressure in a vacuum Gauge pressure = pressure relative to surrounding (ambient) pressure Formulas Ideal Gas Law (macroscopic) 𝑃𝑉 = 𝑛𝑅𝑇 P = pressure in pascals (Pa) V = volume (m 3 ) n = number of moles R = 8.31 J/(mol*K) T = temperature (K) Ideal Gas Law (molecular) 𝑃𝑉 = 𝑁𝑘 𝑇 N = number of particles k B = 1.38 x 10 -23 J/K (Boltzmann constant) Changes for an ideal gas 𝑃 𝑉 𝑇 = 𝑃 𝑉 𝑇 If amount of gas doesn’t change, then PV/T=nR=constant Pressure 𝐹/𝐴 A = area (m 3 ) Class Questions Given initial or final conditions, rearrange ideal gas law to solve for some quantity. Ex. A gas is heated at constant temperature to some volume that is twice the initial volume. If the initial pressure is 100 Pa what is the final pressure? The hot air balloon problem or something similar
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Physics 152 Fall 2017 SI Leader: Hubert Lin Tues. 7:00-9:00PM SI Exam 1 Review Packet ILC S131 Ex. Ha no thanks too complicated to write one. Same steps as usual to solve though. Identify what variables are changing and rearrange the ideal gas law as needed. Like the question above just with more calculations and deciphering what’s actually happening. Internal Energy (E) – energy in a system due to microscopic motion/vibrations and potential energy Higher temperature = higher E for a given system Energy changes due to heat or work Heat (Q) – flow of thermal energy between systems Heat always flows from hotter system to colder system Heat capacity (C) – effect of heat on temperature of a system; depends on material and quantity Specific heat (c) – heat capacity per unit mass (m); depends only on material Latent Heat – when a system goes through a phase change, temperature does not change o Heat of fusion (L f ) – changes between solid & liquid o Heat of vaporization (L v ) – changes between liquid & gas Work (W) – work in thermodynamic systems can be described by equations of state (ideal gas law) Area under PV curve = work done during a process; typically positive for compression, negative for expansion Formulas
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