# Do fields created by magnets add up?

#### SMD1990

If I were to use a gaussmeter to measure the strength of a magnet's magnetic field, would the value read be double if I were to stack two (of the same kind of magnets) on top of one another?

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#### MrNerd

I THINK it might, but I'm not entirely sure. If you're thinking exactly double, probably not, since there is still a difference between the two magnets positions so one spot is technically further. But I think it should be double for the most part.

#### cragar

Well B fields obey superposition. And if we think of amperes law and if i were to double the current enclosed then the B field would double.

#### Pengwuino

Gold Member
Yes, electromagnetic fields obey superposition and will stack as you guessed.

#### SMD1990

Why I was wondering is, I was looking at Magcraft's selection of magnets. Taking into account the differences in thickness, http://www.rare-earth-magnets.com/p-5-nsn0592.aspx" [Broken] of theirs are the strongest.

So if you were to stack them, and their magnetic fields add-up linearly, then they are stronger than individual singular magnets of a greater thickness.

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#### MrNerd

Those itty bitty super magnets are probably made with rare earth materials. Apparently they channel or enhance the magnetic properties of materials or something. I'm not sure why, but I think that's what the article said. They play a major role in allowing us to have miniaturized electronics, so we don't need earbuds the size of an egg or something.

I saw a picture of one holding a foot long wrench in a National Geographic magazine, and it was maybe half a centimeter long(if i had to guess). It looked like a cylinder, for the most part, but angled, so like a hexagon with depth.

#### K^2

Why I was wondering is, I was looking at Magcraft's selection of magnets. Taking into account the differences in thickness, http://www.rare-earth-magnets.com/p-5-nsn0592.aspx" [Broken] of theirs are the strongest.

So if you were to stack them, and their magnetic fields add-up linearly, then they are stronger than individual singular magnets of a greater thickness.
Magnetic fields from two sources add up as vectors at each point. So the strength of the field is not necessarily the sum of the strengths. In extreme case, the fields from two magnets can cancel at certain points.

Assuming same materials and cross-section of bar or cylinder magnets, two magnets of length L/2 stacked together should give you the same field as single magnet of length L.

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#### boyongo

If they go in the same direction the add up. 5Tesla up + 10 Tesla up = 15 Tesla. 10 Tesla up + 5 Tesla down= 5 Tesla. Its all vectors.

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