How to design an electromagnet?

For this reason, there is no point in building an electromagnet with a higher field intensity. Industrial lifting electromagnets are designed with both pole faces at one side (the bottom). This confines the field lines to maximize the magnetic field. It's like a cylinder within a cylinder. Many loudspeaker magnets use a similar geometry, although the field lines are radial from the inner cylinder rather than perpendicular to the face. Notice the large surface area compared with the height. With pole faces of one square foot or more, thousands of pounds can be lifted with drive currents of just a few amperes.