Strong Vs. Weak Magnets

Tiny, cylindrical magnets

Magnets come in a variety of strengths, from tiny compass needles to powerful magnetic resonance imaging (MRI) units. Most, such as refrigerator magnets, are relatively weak, small and inexpensive. However, some are strong enough to erase credit cards.

Materials

The material used to make a magnet dictates its strength. In 2009, neodymium alloys made up the strongest magnets, followed by iron, ceramic and plastic. Neodymium is a soft, silver-colored metal.

Purpose

Strong magnets are typically used to apply large forces to move and hold objects. Weak magnets, such as those used in compasses, are good at detecting magnetic fields.

Considerations

Designers use weaker magnets if safety is an issue, such as for toys. Strong magnets may need warning labels and other safeguards.

Size

A magnet's strength can depend on its size. Generally, the smaller the magnet, the weaker it is.

Cost

Weak magnets are generally easy and inexpensive to make. The strongest magnets are rare and expensive.

References

• Ron Kurtus' School for Champions: Classification of Magnetic Materials
• K&J Magnetics, Inc.: Neodymium Magnet Safety