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Attraction of the block magnet to the steel plate

Rectangular prism shaped permanent magnet is pulled toward the ferromagnetic plate.

Problem type:
Plane-parallel problem of magnetostatics

Geometry:

w=1.5" (38.1 mm) - magnet width;
t=0.25" (6.35 mm) - magnet thickness;
l=0.25" (6.35 mm) - magnet length;
t_pl=0.25" (6.35 mm) - plate thickness;

Given:
magnet grade N35, H_c = 954930 A/m, B_r = 1.26 T;
relative magnetic permeability of the plate μ_steel = 1000.

Task:
Calculate the pulling force of the magnet attraction to the steel plate.

Solution:
To calculate the pulling force accurately, and avoid integration along the edge dividing media with large difference in magnetic permeabilities, we place the magnet at a small distance δ = 0.005" (0.127 mm) from the steel plate. Integration contour is drawn in the air around the magnet.

Result:
Magnetic field of the brick permanent magnet in vicinity of the steel wall.

Pull force

QuickField

74 N

Reference*

65 N (14.3 lb, 1 lb = 4.54 N)