I mean WHY
In: Physics
Because different material is magnetic to a different degree.
The large low strength magnet is often made of powdered iron oxide in some ceramic material to hold it together. They are cheap to make but weak.
The strong magnet is rare-earth magnets that are often made of neodymium that is in a molecule with iron and boron and produces a stronger magnetical field. The material and manufacture cost a lot more so the week magnets are also manufactured.
Neodymium cost around $1 million per tonne compared too iron at around $200 per tonne. Even if the Neodymium magnet only is 20% Neodymium by mass and the rest mostly iron the increased material cost has a large effect on cost.
Magnets are made from different materials. The gray ferrite (ceramic and iron oxide with some other elements mixed in in small proportions) ones hold a magnetic field that is much less dense than more-recent magnet developments. Neodymium magnets (they’re not pure neodymium) for example, are able to take a much stronger magnetic field.
Could be 2 things.
Weaker ferrite magnets and much stronger rare-earth magnets, like neodymium, or “focused” magnets, when the north and south poles of a magnet are arranged in a pattern that concentrates the field closer to the surface trading range for strength. Flat flexible fridge magnets use this, its how they’re able to be stronger without being made of more expensive materials as well as remaining quite thin.
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