PHYSICS · Multi-part · Fermi University Physics · Electricity, Magnetism & Electromagnetism · Electric fields in matter · Electric fields in matter
The Boundary-Value Problem, Ch Molecular polarisability, permanent dipoles and the Clausius-Mossotti relation
Problem
Someone argues: "In steam, the Lorentz local-field correction χe/3 works out to only 2×10−3. That shows the correction is a minor refinement in general: you can always use the macroscopic field E as the field acting on one molecule and only lose a fraction of a per cent. Separately, the Clausius-Mossotti relation predicts εr→∞ when Nvα→3ε0, but no real liquid has ever been measured with an infinite permittivity, so this divergence is just an artefact of dividing by a quantity that happens to vanish, not a statement about anything physical."
((a)) Test the first claim using liquid argon near its boiling point, for which Nvα/3ε0=0.144. Find χe/3 for this liquid and compare it with the steam figure quoted above.
((b)) Explain what the Clausius-Mossotti divergence represents physically, and name one substance in which the corresponding runaway is observed, to assess the second claim.