No open flames or hotplates are needed for this simple, effective demonstrator. The sensitive liquid crystal temperature indicators attached to the front of each of the four metal bars work in the low temperature range, and a beaker of hot water is all that is required for a dramatic demonstration.
The four bars, of copper, aluminum, brass and steel, are firmly held parallel to one another in a rigid molded carrier with a convenient hole for suspension.
Each bar has a cross-sectional area of 30mm2, and its conductivity value is marked on the back of the support. The temperature indicators are marked at 1cm intervals to aid in charting the movement of the temperature gradients.
Within seconds of placing the ends of the bars in hot water, a visible “heat pulse” travels up the copper bar; the steel bar takes several minutes to conduct the heat to its upper end.
Timing the “heat pulses” enables estimates of the relative conductivities to be made for comparison with the given theoretical values.
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