I am reading this book, the part in particular about Eddy-current separation starting at Page 246, in it there is an equation for calculating the "characteristic time with which the induced magnetic field decays in the particle".
$$ \tau = \mu_0\sigma_psb^2 $$
- $\mu_0$ is the permeability of free space
- $\sigma_p$ is the specific electric conductivity of a particle [S/m]
- $s$ is the shape factor of the particle
- $b$ is the particle radius
I am hoping someone can reflect some light on what $s$ is and how to calculate it, "shape factor" isn't very descriptive and I cannot find anywhere in the book describing it in further detail.
This shape factor is also used in the force equations that I am intersted in...
Another part of the equation I am unclear on is $b$, what if the particle is a cube or cuboid, what should the radius be then?