An induced magnet is an object made from a magnetic material that becomes magnetized only when it is placed near or touching another magnet. Unlike a permanent magnet, which always produces its own magnetic field, an induced magnet gains its magnetism temporarily and loses most or all of it once the external magnet is taken away.
How Induced Magnetism Works
Every piece of iron, nickel, or cobalt contains tiny regions called domains. Each domain is like a microscopic magnet with its own north and south pole. In an ordinary, unmagnetized nail, these domains point in random directions, so their magnetic effects cancel each other out and the nail shows no magnetism overall.
When you bring a permanent magnet close to that nail, its magnetic field reaches into the metal and nudges the domains into alignment. Instead of pointing every which way, they start lining up in the same direction, following the external field. The more domains that align, the stronger the nail’s own magnetic field becomes. At this point, the nail is an induced magnet: it can attract other magnetic materials, pick up iron filings, or even stick to a refrigerator door, all because of the borrowed field.
The strength of this effect depends heavily on distance. Magnetic flux density drops off as the gap between the permanent magnet and the material increases. At just 1 mm away from a small magnet, the field can reach around 0.24 tesla. Move a few centimeters away and the effect weakens dramatically. This is why a paperclip sticks firmly when it touches a magnet but barely reacts from across a table.
Which Materials Can Become Induced Magnets
Only certain materials respond strongly enough to become induced magnets. The key group is ferromagnetic materials: iron, cobalt, and nickel, along with alloys that contain them. Steel (iron with carbon), for example, is ferromagnetic. So are specialty alloys like neodymium-iron-boron, which is used to make powerful permanent magnets.
Materials outside this group barely respond to a magnetic field. Aluminum, copper, wood, and plastic will not become induced magnets no matter how strong the external field is. Some materials show an extremely weak response called paramagnetism, but it is far too faint to observe without laboratory equipment and very low temperatures.
Why the Magnetism Is Temporary
The defining feature of an induced magnet is that its magnetism is temporary. Pull the permanent magnet away and the domains inside the material begin to fall back into their random arrangement. The induced magnetic field fades quickly.
How quickly depends on the material. Soft iron loses its magnetization almost immediately once the external field is removed. This makes it ideal for applications like electromagnet cores, where you want to be able to switch magnetism on and off. Steel, by contrast, holds onto some of its alignment after the field disappears. This leftover magnetism is called remanence. Materials with high remanence are described as “magnetically hard,” and they are the ones chosen to make permanent magnets. The terminology is literal: mechanically soft iron loses its magnetism, while harder, carbon-enriched steel retains part of it.
So the same physical process, domain alignment in an external field, is the starting point for both induced magnets and permanent magnets. The difference is whether the material lets go of that alignment or holds on.
Polarity of an Induced Magnet
When a permanent magnet induces magnetism in a nearby piece of iron, the end of the iron closest to the magnet always develops the opposite pole. If you hold the north pole of a bar magnet near a nail, the nearest end of the nail becomes a south pole. This is why the nail is attracted: opposite poles pull toward each other.
The far end of the nail then becomes a north pole. That exposed north pole can attract yet another nail, which develops its own south pole at the contact point. This is how you can create a chain of paperclips dangling from a single magnet: each clip induces magnetism in the next one down the line. Remove the original magnet from the top and the chain collapses as the induced fields disappear.
Everyday Examples
Induced magnetism is happening any time a magnet “sticks” to your refrigerator door. The door itself is not a magnet. It is simply a sheet of steel that becomes temporarily magnetized by the fridge magnet, creating an attraction between them.
Iron filings on a tabletop offer one of the clearest demonstrations. Scattered randomly, they show no magnetic behavior. Bring a bar magnet underneath the table and the filings snap into curved lines tracing the magnetic field. Each tiny filing has become an induced magnet, aligning itself along the field and even clinging to neighboring filings.
Electromagnets rely on the same principle at a larger scale. A coil of wire carrying electric current produces a magnetic field, and a soft iron core inside the coil becomes a powerful induced magnet. When the current stops, the soft iron loses its magnetism almost instantly. This on-off capability is what makes electromagnets useful in everything from scrapyard cranes to doorbells to MRI machines.
Induced Magnets vs. Permanent Magnets
- Source of magnetism: A permanent magnet produces its own field at all times. An induced magnet only becomes magnetic in the presence of an external field.
- Duration: Permanent magnets retain their field indefinitely under normal conditions. Induced magnets lose most or all of their magnetism when the external field is removed.
- Material type: Permanent magnets are made from magnetically hard materials with high remanence, such as neodymium-iron-boron alloys. Induced magnets typically involve magnetically soft materials like pure iron, which align easily but also let go easily.
- Control: You cannot turn a permanent magnet off. An induced magnet can be activated or deactivated by moving the external field closer or farther away.
In practice, the line between the two is not perfectly sharp. A steel screwdriver used around magnets for long enough can pick up a small amount of residual magnetism, becoming a weak permanent magnet on its own. This happens because steel’s higher remanence lets some domain alignment persist. Soft iron, on the other hand, snaps back to its unmagnetized state almost completely.