Lorenz Number for High-Purity Copper

Abstract

Following a recent report that the Lorenz number, $L=\frac{\ensuremath{\lambda}}{\ensuremath{\sigma}T}$, does not approximate to the theoretical value of $2.45\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}W$ ohm ${\mathrm{deg}}^{\ensuremath{-}2}$ for very pure copper at the lowest temperatures, measurements have been made of thermal and electrical conductivities on copper of similar purity. Between 2 and 4\ifmmode^\circ\else\textdegree\fi{}K, values of $L$ are observed lying in the range ${2.5}_{4}$ to ${2.4}_{0}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}W$ ohm ${\mathrm{deg}}^{\ensuremath{-}2}$.