# Electromagnet pull field

## Main Question or Discussion Point

I was inquiring about how much force will a 1000 lb pull force electromagnet pull at 4-6 inches away from the magnet

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The precise shape and strength of the magnetic field will depend in a complex way on the shape and materials of the magnet.

There is no way of knowing.

it is a 6 inch radius and it is cylinder shaped pulling a 4 inch cylinder shaped object

in a complex way
That's science-speak for 'impossibly complicated and impossible to know without doing lots and lots and lots of careful measurements and probably not even then'

A quick guesstimation, involving the simply geometric assumptions and properties, I would put the force at 4 and 6 inches at 360 lb and 250 lb respectively. Of course, as already stated, materials, configurations, etc., could be chosen to blow this out of the water.

Assuming the magnet is a sphere with a 6 inch radius, the 1000 lb force is effective at 6 inches from the magnet. Thus 4 and 6 inches from the magnet becomes 10 and 12 inches respectively. Simplest force law representation is the inverse square law, m/r^2. Since m/r^2 = 1000 where r = 6 at the magnet surface, then m = 3600. Now solve for other r. Note: this is only roughly valid in the units provided, and a slew of other assumptions about geometry and material properties. But probably good enough for many purposes.

Yea, my first thought was to attempt a simple 1/r^2 solution but I decided the likely geometry of a magnet would be flat pole pieces. The approximation to a sphere is just too wild for my taste.

I should imagine this is a ring magnet anyway. The field would be highly localised.

Yea, my first thought was to attempt a simple 1/r^2 solution but I decided the likely geometry of a magnet would be flat pole pieces. The approximation to a sphere is just too wild for my taste.

I should imagine this is a ring magnet anyway. The field would be highly localised.
Yes, if the magnet is flat, and the 1000 lb pull is at the flat surface, you've blown my calculation out of the water :tongue:

the magnet is 6 inch radius flat surface it has a pull force of 1000 lbs kinda shaped like a can and the object it is pulling would be on my first guess a iron core object but i am open to any suggestions i just wanted to have a good idea of how much becuase it cost alot to buy the magnet

Redbelly98
Staff Emeritus