How close must a magnet get to pull?

Sometimes a fridge magnet seems to give a little tug just before it touches the fridge door. A magnet is an object that pulls on certain kinds of metal. How close must a magnet get to pull?

Let's follow a parent trying a large magnet beside a steel spoon on a table. Steel is a kind of metal that magnets often pull on. This spoon sticks to a magnet, though not every metal spoon does.

Around the magnet is a magnetic field, the invisible space where its push or pull can reach. The magnetic field lets the magnet pull on the steel spoon without touching it. Nothing like a string joins them together.

That magnetic field does not have a sharp edge where the pull suddenly starts. Farther away, the magnet's pull gets weaker. Closer to the magnet, the pull gets stronger.

The parent puts the magnet far from the steel spoon to start. The spoon stays still because the pull there is too weak to move it. The parent keeps hold of the large magnet throughout this little test.

Now the parent slowly brings the magnet closer, leaving a little space beside the spoon. Can you guess whether the pull gets stronger or weaker? The spoon has not moved yet, but the space between them keeps shrinking.

Stronger is the answer! As the parent brings the magnet nearer, its magnetic field pulls harder on the spoon. Soon the pull is strong enough, and the spoon slides toward the magnet.

The spoon begins moving before the magnet touches it. So touching is not the thing that starts the pull. Getting close enough makes the pull strong enough to move this spoon.

But there is no single distance that works for every magnet. With the same spoon and table, a stronger magnet can usually move the spoon from farther away. A weaker magnet needs to come closer because its pull is weaker.

The surface matters, too. If the parent puts the spoon on a rough cloth, the cloth can hold it back more than the smooth table does. The magnet may need to come closer so its pull can overcome that extra rubbing.

Magnet, steel spoon, magnetic field, closer, stronger pull, moving spoon. A magnet must get close enough for its pull to move the object, and that distance depends on the magnet, the object, and what holds the object back.

You have discovered a little invisible tug behind an everyday wonder.