Okay, so this is kind of a goof-off question, but it's part of an of educational game that I've been playing with myself for years. If you don't want the background then skip to the horizontal rule, below which I'll ask the actual question.

The essential idea of the game is that you're stranded on an undeveloped Earth-like world with no tools, and you have to develop a semi-modern computer (and all of the pre-requisite technologies). There's a caveat though: You can't assume access to rare materials. Significantly, this means no access to natural magnets, at least until you can create strong magnets easily. The idea of the rule is to necessitate learning about all of the technologies that could possibly be needed.

The specific hurdle I'm facing in this case is the creation of permanent magnets for use in electrical generators. Assuming I have access to varieties of plants and refine basic metals (iron, copper, possibly even steel) and can make good wires and such, I had previously decided that I could use the magnetic field of a copper wire that's attached to a lemon or potato battery, or similar device. I was just reading though, and I'm not sure that this could produce a sufficiently powerful magnet in any reasonable amount of time, so I wanted to ask for advice.

I'm trying (in my imagination) to create permanent magnets using only metals, wires, and readily available natural materials, or tools/mechanisms that can be created from them. My current plan is to use coiled copper wire to magnetize iron, with fruit and vegetable batteries, but I think it's inadequate.

Is there a better way to create my first permanent magnets, or else can fruit/vegetable batteries produce enough current to create permanent magnets strong enough to power a generator?

Any replies appreciated. Requests for clarification also welcome. Thank you for your time.

  • $\begingroup$ You may already know this but just to address the battery aspect: remember that the fruit is not the source of the voltage, it's just an electrolyte-- a medium for the chemistry to take place. The two metals, the anode and the cathode are the source of the voltage. $\endgroup$
    – pentane
    Feb 18, 2015 at 18:39

1 Answer 1


I don't think you have noticed one of the ways that the experimenters of old did it.

Here is a link to some of Joseph Henry's student notes, gathered by the Joseph Henry project at Princeton.

If your world has a magnetic field, then you can simply hold a small ferromagnetic bar so that the local planetary magnetic field is roughly aligned with the bar and then strike the end a few times with a hammer. This will magnetize it. A quick explanation is that the shock waves give the domain system enough energy to "jump" out of its current local minimum energy configuration to find a new, lower energy configuration with the domains more aligned to the planet's field than they were before.

You repeat this a number of times with small bars, and then you gather them together into a bundle. You can thus create a fairly strong permanent magnet, which now gives you the ability to magnetize other things with the stroking method that is also given in Henry's notes.

  • $\begingroup$ Oh, nice! I'd heard about this as a method for making magnets from other magnets, but this is the first time I've seen it used as an initial method. Probably I just wasn't paying attention in the past. Thanks! $\endgroup$
    – Khatharr
    Feb 18, 2015 at 14:15

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