Why do two magnets sometimes snap together and sometimes shove apart?
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Why do two magnets sometimes snap together and sometimes shove apart?
The short answer
Two magnets pull together or push apart depending on which ends are facing each other, not on whether the magnet is simply 'sticky.' Every magnet has two opposite ends — a north pole and a south pole. Opposite ends pull together; matching ends push apart.
How it works
The pull of a magnet lives at its two ends, which scientists call poles: one north and one south. When you bring two magnets close, a north end and a south end attract and snap together, while two north ends or two south ends repel and shove apart. Flipping one magnet around swaps which end is facing, so the very same pair can switch from pushing to pulling. The force grows quickly stronger as the gap between them shrinks.
What people get wrong
A common belief is that a magnet is either 'sticky' or it isn't, as if attraction is a fixed property of the magnet. It isn't. The same two magnets can either snap together or refuse to touch depending only on which ends point at each other. Turn one magnet around and a shove becomes a snap, which shows the behavior comes from the ends (poles), not from the magnet being magic-sticky.
The catch
Each behavior is useful for a different job. Opposite ends attracting clamp together tightly, which is great for holding a note on the fridge or latching a cabinet, but once stuck they don't easily let go. Matching ends repelling create an invisible springy cushion that can even make a magnet float — the idea behind maglev trains — but that floating is wobbly and tends to slip sideways or flip over unless something keeps it lined up.
Questions kids ask
Why does flipping one magnet change a push into a pull?
Each magnet has a north end and a south end. Flipping one magnet swaps which end faces the other magnet. If matching ends were facing (a push), flipping makes opposite ends face instead, which pull together. Only the facing ends changed, not the magnets.
Do opposite ends of magnets attract or repel?
Opposite ends attract: a north end and a south end pull toward each other. Matching ends repel: two north ends, or two south ends, push apart.
What happens if you cut a magnet in half?
You don't get one piece with only a north end and one with only a south end. Each half instantly becomes a complete smaller magnet with its own north and south end. There is no such thing as a magnet with a single end.
Why does the pull feel stronger when the magnets are closer?
The magnetic force between two magnets grows quickly stronger as the gap between them shrinks, so the last little bit before they touch feels like a sudden hard snap rather than a gentle tug.
For grown-ups
Every magnet is a dipole with a north and a south pole that always occur together; isolated magnetic monopoles have never been observed. Like poles repel and unlike poles attract because the force follows the magnetic field lines, which emerge from the north pole and re-enter at the south. For two small magnets the attraction or repulsion strengthens steeply as they approach, falling off faster with distance than gravity's inverse-square law. Cut a magnet in half and you don't isolate a single pole — each piece becomes a complete smaller magnet with its own north and south.