George Frederick Charles Searle was born December 3rd, 1864 and was a British Physicist and Lecturer. Searle first began working at the University of Cambridge in 1888 at the age of 24 under the supervision of J. J. Thompson. He continued his work for another 55 years. Searle is best known for his contribution to the research on the velocity dependence of electrostatic mass which played an important role in the formulation of Einstein’s special theory of relativity. Along with these achievements, the Searle’s Bar experiment was produced, a simple and affordable way to calculate the thermal conductivity of good thermal conductors.
It is important to note that for this experiment to be successful, the rod being measured must be a good thermal conductor.
Most metals are considered good thermal conductors thus any metal rod would be suitable for this experiment. Common materials with high enough thermal conductivities include: Copper, Stainless Steel and aluminum.
Specific Heat of Water = 4.18 Joules/(gram⋅°K)
Energy absorption of water (Q) = c ⋅ m ⋅ ΔT
Heat Flow Rate (Q) = k ⋅ A ⋅ (T1-T2) / d
Cross sectional Area = πD2 / 4 OR πr2
|Materials Required||Price||Location of Purchase|
|Steam Chamber/Maker||Varying Price||Varying Locations|
|Thermometer x4||$10 x4 = $40||Amazon.com|
|Insulating Material(Cotton or Felt)||$10||Amazon.com|
|Metal Rod||Varying Price||Speedymetals.com|
*For how to make your own Steam Chamber, See Lee’s Disc Experiment*
The Rate of Heat transfer between thermometers 1 and 2 over a given distance d will be given by the formula:
This Formula can be rearranged to produce the following:
The amount of energy absorbed by the water is given by:
With this formula in mind, Q of equation (2) can be replaced by the equation (3) producing the following:
A simple insertion of the values experimentally obtained can be performed to calculate the thermal conductivity of the metal in question
Once calculated, the experimental thermal conductivity constant of a given material can be compared to the experimental thermal conductivities obtained by highly specialized labs.
|Type of Material||Thermal Conductivity Constant (W/mK)|
*Thermal Conductivity values taken from the Thermtest thermal properties database, for more Thermal Conductivity values visit: https://thermtest.com/materials-database
Unlike the Lee’s Disc experiment, the Searle’s Bar experiment is intentionally designed to calculate the thermal conductivity of materials with high thermal conductivities. Metals are generally considered the better thermal conductors due to their highly order molecular arrangement however there are some non-metals which can surpass metals in thermal conductivity such as Graphene.
Using this list of instructions, anyone can become a thermal physicist and calculate the thermal conductivity of various metals for an affordable price.
Web Resources for further Information:
To make your own simulation:
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