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Main >> Applications >> Sample problems >> Attraction of the block magnet to the steel plate

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:
Attraction of the block magnet to the steel plate Rectangular prism shaped permanent magnet is pulled toward the ferromagnetic plate Steel Permanent magnet t l w d δ

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

Given:
magnet grade N35, Hc = 954930 A/m, Br = 1.26 T;
relative magnetic permeability of the plate μsteel = 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.
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)

* Reference: www.kjmagnetics.com.

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