This Demonstration shows the solution to the heat equation for a one-dimensional rod. The rod is initially submerged in a bath at 100 degrees and is perfectly insulated except at the ends, which are then held at 0 degrees. This is a a Sturm–Liouville boundary value problem for the one-dimensional heat equation
with boundary conditions , , and , where is time, is distance along the rod, is the length of the rod, and .
The solution is of the form
where is the conductivity parameter (a product of the density, thermal conductivity, and specific heat of the rod) and
If you increase the number of terms , the solution improves as long as the time is small. As (the final state), the entire rod approaches a temperature of 0 degrees. You can see the effect of the thermal properties by varying the conductivity parameter .