Changes

In the first part of this tutorial lesson, you simulated a permanent magnet cylinder of height 50mm. In the second part, you simulated two parallel magnet cylinders of height 20mm separated by a spacing of 10mm. The total height of the whole structure is still 50mm. In this part of the tutorial lesson, we are going to treat the spacing between the two cylinders as an air gap and will parameterize its height as a variable called "gap_h". In other words, we will allow the heights of the two cylinders to vary. But we will require the bottom base of "Cyliner_1" to be fixed at Z = 0 and the top base of "Cylinder_2 " to be fixed at Z = 50mm.