How a Magnet Picks Up a Paperclip

Hold a refrigerator magnet half an inch above a steel paperclip lying on a desk. Nothing happens. Lower it another quarter inch and the paperclip jumps up to meet it. The paperclip was not magnetic a moment ago. So where did the pull come from?

Here is the cartoon version most people carry around: magnets stick to metal. That is the part to throw out first. A magnet will not pick up a penny, a strip of aluminum foil, or a copper wire, even though all three are metals. It only grabs iron, nickel, cobalt, and steels that contain them. Something specific is going on inside those particular materials.

Every atom of iron behaves like a tiny magnet on its own, with a north pole and a south pole. In a normal, un-magnetized paperclip, the atoms are organized into small neighborhoods called magnetic domains. Inside one domain, all the atoms point the same way, like a marching band facing east. But the next domain over might face west, and the one after that north. Across the whole paperclip, the directions cancel out. The paperclip contains millions of tiny magnets, but they fight each other to a draw, so from the outside it acts like nothing.

Now bring the refrigerator magnet close. The refrigerator magnet produces a magnetic field, an invisible region of influence that pushes and pulls on other magnets. That field reaches into the paperclip and starts twisting the domains. Domains already pointing toward the magnet grow larger. Domains pointing the wrong way shrink or flip. Within a fraction of a second, most of the paperclip's domains line up in the same direction. The paperclip has become a magnet itself, with its north pole facing the refrigerator magnet's south pole. Opposite poles attract, and the paperclip jumps.

This explains why a paperclip can pick up a second paperclip while it is stuck to the magnet. The first paperclip is now a working magnet, so it can align the domains of the second one. Pull the chain away from the original magnet, though, and the effect fades. Without the outside field holding them in formation, the domains in soft steel drift back out of alignment, and the chain falls apart. This temporary magnetism is called induced magnetism.

So why not copper? Copper atoms do not behave like tiny magnets in the same way iron atoms do. There are no domains to align. You can bring the strongest magnet in the world close to a copper penny and there is nothing inside the penny for the field to organize. The field passes through and the penny sits there.

The answer to the opening question is that the magnet did not reach out and grab the paperclip from a distance. It reached in and rearranged the paperclip until the paperclip pulled itself toward the magnet.