The dimensionless magnetic Reynolds number, , is also used in cases where there is no physical fluid involved.
: &times; (characteristic length) &times; (characteristic velocity)
::where
:: is the magnetic permeability
:: is the electrical conductivity.
For  the skin effect is negligible and the eddy current braking torque follows the theoretical curve of an induction motor.
For  the skin effect dominates and the braking torque decreases much slower with increasing speed than predicted by the induction motor model.