IB›IB Physics HL›Mind mapsB.1 Thermal energy transfersIB Physics HL: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsParticle modelSolids: particles vibrate about fixed positionsLiquids: close, but move past each otherGases: far apart, random, interact in collisionsρ=mV\rho = \frac{m}{V}ρ=VmMean kinetic energy: Eˉk=32kBT\bar{E}_k = \frac{3}{2}k_B TEˉk=23kBTInternal energyIntermolecular potential plus random kinetic energyThermal energy flows from hot to coldPhase change happens at constant temperatureEnergy raises potential energy, not kineticHeating calculationsTemperature change: Q=mcΔTQ = mc\Delta TQ=mcΔTPhase change: Q=mLQ = mLQ=mLHeater: Q=PtQ = PtQ=PtVaporization needs more energy than fusionMulti-stage: solve stage by stageThermal energytransfersKJWcLConduction, convectionConduction: ΔQΔt=kAΔTΔx\frac{\Delta Q}{\Delta t} = kA\frac{\Delta T}{\Delta x}ΔtΔQ=kAΔxΔTMetals conduct well due to free electronsTrapped still air has very low kConvection: warm fluid less dense, risesRadiationLuminosity: L=σAT4L = \sigma A T^4L=σAT4Brightness: b=L4πd2b = \frac{L}{4\pi d^2}b=4πd2LWien: λmaxT=2.9×10−3 m K\lambda_{max}T = 2.9\times10^{-3}\,\text{m K}λmaxT=2.9×10−3m KRed star is cooler than a blue oneExam tipsChange of 1 K equals change of 1 °CUse kelvin for temperature ratios and T4T^4T4Convert nm to m in Wien's law