How to calculate the “load line”, using the capacity of a magnet to hold an item?
Holding capacity refers to the ability of a magnet to apply force to either another magnet or a piece of a magnetically permeable material (like an iron based soft magnet). There are equations that relate to the shape of a magnet and its potential ability to hold another piece of ferromagnetic, material. If F is the force between the two objects: F = AB2/8π (where the units of F are dynes) Where A is the area of contact and B is the induction in the magnet (in Gauss). The trick is calculating B, since it is some point on the demagnetization curve of the material that the magnets are made of, specifically the place where the geometry dependant load line intersects it. The “normal” load line, Bd/Hd, can be calculated using Bd/Hd = (Lm/Am)(πS)1/2 where Lm is the thickness of the magnet, Am is the area of the magnet, and S is one half of the exposed surface area of the magnet (the sides and backs, etc.). For example, if there are 2 rectangular magnets (1 cm x 1 cm x 0.5 cm thick, with the
