Magnetism is a fundamental force in nature, generated by the motion of electric charges. A moving electric charge creates an invisible area of influence called a magnetic field. Materials respond to this field based on the internal arrangement of their constituent electrons. In certain materials, the magnetic effects of electrons align to create a noticeable magnetic response. The way these materials are processed determines which of the three main types of magnets they become.
Permanent Magnets
Permanent magnets retain their magnetic properties without requiring an external power source. Their persistent magnetic field results from a highly ordered internal atomic structure. Groups of atoms form microscopic regions called magnetic domains, where electron magnetic moments are aligned. During manufacturing, a strong external field forces these domains to align permanently, even though they point randomly in an unmagnetized state.
This lasting alignment is characteristic of magnetically “hard” materials, which possess high coercivity and strongly resist demagnetization. Modern permanent magnets fall into two main categories based on strength and composition. Neodymium magnets, a rare-earth alloy, are the strongest commercially available, used in high-performance applications like computer hard drives and headphones. Ceramic or Ferrite magnets are less powerful but are inexpensive, highly resistant to corrosion, and perform reliably in high-temperature environments, making them suitable for common items like refrigerator magnets.
Temporary Magnets
Temporary magnets are materials that only exhibit magnetic properties when they are within a strong external magnetic field. Once the external field is removed, they lose their magnetism almost immediately. This phenomenon is known as induced magnetism, where the external field momentarily forces the electron domains within the material to align. Materials suitable for this purpose are considered magnetically “soft” because they have very low coercivity.
Soft iron is the most common example of a temporary magnetic material. When a permanent magnet is brought near a paper clip, the clip is temporarily magnetized and can attract other clips, but it instantly ceases to be a magnet when the first magnet is pulled away. This ease of magnetization and demagnetization is essential for devices where magnetism must be quickly turned on and off. Their application is most often found within the core of electromagnets.
Electromagnets
Electromagnets are magnets whose field is created and controlled entirely by electricity. They are typically constructed by coiling a conductive wire, known as a solenoid, around a ferromagnetic core, usually soft iron. When an electric current is passed through the solenoid, it generates a magnetic field. This field is then intensified by the soft iron core, which becomes a temporary magnet itself, significantly multiplying the strength of the overall field.
The primary advantage of electromagnets is the ability to precisely control the magnetic field. The strength of the magnetism is directly proportional to the amount of electric current flowing through the coil and the number of wire turns. Furthermore, the polarity of the electromagnet can be instantly reversed simply by changing the direction of the current flow. This variable control makes them indispensable for heavy industry and advanced technology, such as massive industrial cranes and Magnetic Resonance Imaging (MRI) machines.