Electromagnetic (EM) yokes are U-shaped cores of soft iron, usually laminated, with a coil wound around the base of the U. When we pass an electric current through the coil the result is a North and South Pole at the ends of the core. This makes it look like a horseshoe magnet. It is possible to vary field strength using varying current and the EM yoke is also easy to place onto and remove from the part as no field exists until current is applied. This is usually done for larger or irregular shaped parts.