You probably already know that magnets are attracted to specific metals and have north and south poles. When opposite poles are near each other, they attract, while like poles push each other away. But these facts don’t answer the basic questions: What causes a magnet to stick to certain metals? Why don’t they stick to other materials? And why do they attract or repel each other based on their position? Let’s find out.
A magnet is any material or object that creates a magnetic field, an invisible area of magnetism that surrounds it. This force occurs because electric charges are in motion.
All substances are composed of tiny units called atoms. Within each atom, there are electrons that carry electric charges. These electrons spin around the nucleus (or core) of the atom, resembling spinning tops. As they move, they generate an electric current and behave like miniature magnets.
In most materials, the number of electrons spinning in opposite directions is equal, resulting in the cancellation of their magnetism. That’s why substances like cloth or paper are considered weakly magnetic. However, in materials such as iron, cobalt, and nickel, most electrons spin in the same direction. This alignment makes the atoms in these substances strongly magnetic, although they are not yet magnets themselves.
The magnetic field of a cylindrical bar magnet, computed accurately
To become magnetized, a strongly magnetic substance like iron must enter the magnetic field of an existing magnet. All magnets possess north and south poles, and these poles have distinct behaviors. North poles are where the magnetic field points outward, while the south poles are where the field points inward (see the image above). So, by rubbing a piece of iron against a magnet, the atoms within the iron align their north-seeking poles in the same direction. The aligned atoms generate a magnetic field, transforming the iron into a magnet. This is called magnetization.
Certain materials can be magnetized by an electric current. When electricity flows through a wire coil, it produces a magnetic field. However, once the electric current is switched off, the magnetic field around the coil dissipates.
Magnetic fields have the ability to pass through various materials, not limited to just air. You might have experienced this yourself with notes attached to your refrigerator door using colorful magnets with magnetic fields cutting through paper. Or when using a magnet to pick up a long chain of paper clips, where each clip becomes magnetized and attracts the next one. This means that magnetic fields can penetrate magnetic materials like iron.
The magnetic field of two attracting cylindrical bar magnets
The magnetic field of two repelling cylindrical bar magnets
In the 12th century, people found that they could use lodestone, a mineral rich in iron, to make a compass. They did this by rubbing lodestone on an iron needle in one direction. The needle became magnetized and would point north-south when hung up. Scientist William Gilbert later explained that Earth itself acts like a huge magnet with its own north and south poles, causing the magnetized needles to align in this way.
Today, magnets have countless applications in our everyday lives. They are used in MRIs, electric motors, generators, and speakers. They help in powering refrigerators, doorbells, and magnetic toys. Scientists and engineers are constantly finding new ways to harness the power of magnetism.
Words of wisdom
“Science is magic that works.” —Kurt Vonnegut
“Nothing in life is to be feared, it is only to be understood. Now is the time to understand more, so that we may fear less.” —Marie Curie
“What I love about science is that as you learn, you don’t really get answers. You just get better questions.” —John Green
“Science is organized knowledge. Wisdom is organized life.” —Immanuel Kant