Paperclips are not magnets in their normal state, but they exhibit a strong attraction to magnets because they are highly susceptible to becoming temporary magnets themselves. This process, known as induced magnetism, is why a paperclip can hang from a magnet and even support a small chain of other paperclips. The physics involves the internal structure of the metal, which allows it to respond instantly to an external magnetic field. The difference between a paperclip and a permanent magnet lies in how long that induced magnetic effect lasts once the external field is removed.
What Paperclips Are Made Of
Standard paperclips are typically made from steel wire, a material whose magnetic properties are rooted in its primary component, iron. Steel is an alloy of iron and carbon, and the high concentration of iron makes the paperclip react readily to a magnet. Iron belongs to a class of substances called ferromagnetic materials, which also includes nickel and cobalt.
Ferromagnetic materials are distinct because they are the only ones that show a strong attraction to a magnet and possess the ability to become magnetized themselves. This interaction is much more intense than the weak magnetic responses seen in most other materials.
How Magnetic Domains Work
The ability of a paperclip to become temporarily magnetic is explained by the microscopic structure within its steel. Inside the metal, there are countless small regions known as magnetic domains, which are essentially tiny, pre-existing magnets. Within each domain, the magnetic fields of the atoms are aligned, creating a uniform magnetic direction.
In a paperclip not near a magnet, the magnetic domains are oriented randomly in all directions. These scattered alignments cancel each other out, resulting in no net external magnetic field, meaning the material is unmagnetized.
When a strong external magnet is brought close, its magnetic field penetrates the paperclip and influences these random domains. The external field causes the domains to rotate and align themselves with the field’s direction. As domains align, their individual magnetic effects combine, transforming the entire paperclip into a temporary magnet.
This alignment creates a magnetic pole in the paperclip opposite to the pole of the external magnet, causing the strong attractive force. This process allows the paperclip to stick to the magnet and hold up a chain of other clips.
Why Paperclips Only Magnetize Temporarily
The reason a paperclip loses its magnetism so quickly involves the specific type of steel used, which is classified as a “soft” magnetic material. Soft magnetic materials are characterized by their ability to be easily magnetized and demagnetized, requiring minimal energy for the internal domains to shift alignment.
Once the external magnetic field is removed, the forces keeping the domains aligned are gone. The material’s internal structure allows the domains to quickly revert to their random orientations, causing the collective magnetic field to collapse almost immediately.
This contrasts with “hard” magnetic materials, which are used to make permanent magnets. Hard materials require a strong field to align their domains, but once aligned, the domains resist returning to a random state. Paperclips use soft steel because it is a practical choice for function and cost, despite resulting in only temporary magnetism.