# Formula for electromagnet strength parallel, outside the coil

I am working on a electromagnet project to collect metal shavings off the floor after machining.

I have a formula for the magnetic strength at a distance from the ends, but not parallel to the coil. How do I calculate F parallel to the coil?

The formula I have now is: $$F = \dfrac{(NI)^2 μ_0 A}{2 g^2}$$

[ Edit - formula from http://depts.washington.edu/mictech/optics/sensors/week2.pdf ]

Here is a visual example of what I am looking for:

• Your image link appears to be broken. If you clock on the "add image" button in the qjestion editor, you can upload & insert the image directly into your post. – Robherc KV5ROB Feb 1 '16 at 16:24
• You would do better to bend your electromagnet core into a U or otherwise construct a core that allows both ends to point at the floor for more effective pickup. If you are trying for a wide path, many magnets. This type of device (magnetic sweeper) is also implemented commercially with many rare earth magnets...no pesky power cord. – Ecnerwal Feb 2 '16 at 0:31