IB›IB Physics SL›Mind mapsB.1 Thermal energy transfersIB Physics SL: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsMolecular modelSolids: particles vibrate about fixed positionsLiquids: close together, move past each otherGases: far apart, random, interact in collisionsT(K) = θ(°C) + 273Eˉk=32kBT\bar{E}_k = \frac{3}{2}k_B TEˉk=23kBTInternal energyTotal intermolecular PE plus random KEThermal energy flows from hot to coldPhase change happens at constant temperatureEnergy goes into intermolecular potential energyHeating calculationsQ=mcΔTQ = mc\Delta TQ=mcΔTQ=mLQ = mLQ=mLHeater: Q=PtQ = PtQ=PtMulti-stage problems: solve stage by stage, add energiesThermal energytransfersKJWConduction, convectionConduction rate: ΔQΔt=kAΔTΔx\frac{\Delta Q}{\Delta t} = kA\frac{\Delta T}{\Delta x}ΔtΔQ=kAΔxΔTMetals have free electrons, so conduct wellStill air has very low k: good insulatorConvection: warm fluid expands, rises, cool sinksThermal radiationLuminosity: L=σAT4L = \sigma A T^4L=σAT4Brightness: b=L4πd2b = \frac{L}{4\pi d^2}b=4πd2LWien: λmaxT=2.9×10−3\lambda_{max}T = 2.9 \times 10^{-3}λmaxT=2.9×10−3 m KHotter star peaks at shorter wavelengthExam tipsTemperature ratios need kelvinConvert nm to m before Wien's lawUse kelvin in T4T^4T4; errors are enormousLatent heat of vaporisation is much larger than fusion