# Magnets: Size Matters

*Most recent answer: 10/22/2007*

Q:

Would a magnet of a longer length have a longer magnetic field than a magnet of a shorter length, assuming that they both are made of the same materials and that they have the same width and height.

- Adam (age 16)

NH

- Adam (age 16)

NH

A:

I guess by ’longer magnetic field’ you mean ’field keeping at least
some minimum strength out farther away’. The answer is yes.

Far away from the magnet, the field strength falls off as the cube of the distance. For a uniformly magnetized material, the strength of that field will be proportional to the volume of the magnet. If a magnet is twice as long, with other dimensions fixed, its field far away will be twice as strong. That means that it would stay above any fixed minimum strength out to the cube root of 2 times as far, around 26% farther.

Mike W.

Far away from the magnet, the field strength falls off as the cube of the distance. For a uniformly magnetized material, the strength of that field will be proportional to the volume of the magnet. If a magnet is twice as long, with other dimensions fixed, its field far away will be twice as strong. That means that it would stay above any fixed minimum strength out to the cube root of 2 times as far, around 26% farther.

Mike W.

*(published on 10/22/2007)*