When the iron core is inserted inside the energizing solenoid, the iron core is magnetized by the magnetic field of the energizing solenoid. The magnetized iron core also becomes a magnet, so that the magnetic properties of the solenoid are greatly enhanced because the two magnetic fields are superimposed on each other. In order to make the electromagnet more magnetic, the iron core is usually made into a shoe shape. However, be aware that the coils on the hoof-shaped iron core are wound in opposite directions, clockwise and the other side must be counterclockwise. If the winding directions are the same, the magnetization of the two cores against the iron core will cancel each other, making the iron core non-magnetic. In addition, the core of the electromagnet is made of soft iron and cannot be made of steel. Otherwise, once the steel is magnetized, it will remain magnetic for a long time and cannot be demagnetized. The magnetic strength cannot be controlled by the magnitude of the current, and the advantages of the lifting electromagnet are lost.