# "Optimal Electromagnet Shape to Attract a Steel Ball. I have an application where I need an electromagnet that generates a pull force on a ~10mm diameter steel ball that is initially ~10mm from the electromagnet. For a single coil electromagnet with a fixed number of turns and current, is there a core shape that provides the highest attraction force versus distance for a steel ball of a given diameter?"

Optimal Electromagnet Shape to Attract a Steel Ball
I have an application where I need an electromagnet that generates a pull force on a ~10mm diameter steel ball that is initially ~10mm from the electromagnet.
For a single coil electromagnet with a fixed number of turns and current, is there a core shape that provides the highest attraction force versus distance for a steel ball of a given diameter?
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Coleman Ali
The most pull will be had when as many of the field lines connecting the two poles of the electromagnet as possible travel through the steel ball. This means bending the core upon which the magnet is wound into a "U" shape with the ends of the "U" contoured to cradle the ball. Ideally they would be machined into a concave shape that closely matches the shape of the ball. This setup will tend to strongly pull the ball into the magnet.
Note that with time, both the core and the ball will tend to become magnetized, causing the ball to stick in place even after the coil is disconnected. You can cancel this tendency by reversing the polarity of the coil connections with each successive energization of the coil, but this requires some smarts in the drive circuit for that coil.