Searle's bar method
Introduction '''Searle's bar method''' (named after George Frederick Charles Searle) is an experimental procedure to measure thermal conductivity of material. A bar of material is being heated by steam on one side and the other side cooled down by water while the length of the bar is thermally insulated. Then the heat Δ''Q'' propagating through the bar in a time interval of Δ''t'' is given by:where* Δ''Q'' is the heat supplied to the bar in time Δ''t''* ''k'' is the coefficient of thermal conductivity of the bar. * ''A'' is the cross-sectional area of the bar,* Δ''T''bar is the temperature difference between each end of the bar* ''L'' is the length of the barand the heat Δ''Q'' absorbed by water in a time interval of Δ''t'' is::where* ''C''w is the specific heat of water,* Δ''m'' is the mass of water collected during time Δ''t'',* Δ''T''water is difference in the temperature of water before and after it has gone through the bar.Assuming perfect insulation and no energy loss, then :which leads to :
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