Magnetic drag in the quasi-static limit: Experimental data and analysis

Abstract

Experimental details concerning measurements of the deceleration of Al and Cu disks rotating under the influence of a localized, nonuniform magnetic field are discussed. For a specified magnetic field distribution, the deceleration of the disk is measured as a function of radial location of the field from the rotation axis and the magnetic drag coefficient at each point is calculated. The measured values of the drag coefficients are compared to theoretical predictions and excellent agreement is obtained.

Design of a magnetic braking system

“…Marcuso et al [13] computed the braking force on a rotating disk under non-uniform magnetic field. Experimental results are close to the theoretical predictions except near the disk edge [14]. The edge effects on the braking torque are further revealed by Aguirregabiria et al [15].…”

Magnetic braking revisited

“…In the experimental setup of Marcuso et al, 5,6 a/R d ϭ0.3 or larger, which prevents us from using our calculations to explain quantitatively the decreasing trend of the torque near the border, because then the footprint will encompass the border and the cylindrical symmetry inside the disk will be broken. However, the tail of the displayed curve may explain qualitatively the decreasing of the torque near the border that they observed experimentally but could not explain, even qualitatively, with the analytical expression they obtained.…”

“…Marcuso et al 5,6 made use of a method of successive approximations to solve Maxwell's equations in order to compute the braking force on a rotating disk under the action of a static external nonuniform magnetic field. The braking torque was compared with the experimental results for disks of aluminum and copper, obtaining very good agreement except near the disk border.…”

Maglev for students

“…Heald [14] presented an improved theory of this experiment. Marcuso et al [15,16] computed the torque on a moving conductor by a localized magnetic field and confirmed the calculations by measurements of the deceleration of aluminium and copper discs rotating in the magnetic field. Aguirregabiria et al [17] studied the braking effect on a thin conducting disc rotating in a nonuniform magnetic field.…”