A device with an iron core inside and using a coil with current to make it magnetic like a magnet is called an electromagnet. The iron core should be made of soft iron or silicon steel that is easy to be magnetized and easy to lose magnetism. Such an electromagnet is magnetic when it is energized, and disappears when it is powered off. Electromagnets have extremely wide applications in daily life. The invention of the electromagnet has also greatly improved the power of the generator.