This past week I’ve taken an interesting tour into the world of magnets and magnetism, and acquired a much better understanding of them. A few key points:
*Discussing iron and steel magnets only. Magnetite is the only other material readily available through recorded history.
*Magnetic materials have magnetic domains that can be aligned.
*Different materials have differences in densities of magnetic domains and how readily those domains can be aligned.
*‘Strength’ is referring to the magnetic flux measured in teslas (webers per sq. meter)
*Magnets can only be increased in strength until they are saturated, so for any material the density of it’s magnetic domains determines a maximum strength for a magnet. Once all the domains are aligned the magnet can’t get any stronger.
A piece of iron can be hammered while it is cold and physically aligned in the Earth’s magnetic field. The hammering causes magnetic domains in the iron to become aligned with that magnetic field. The Earth’s magnetic field is very weak but the hammered magnet can have a greater strength than that. I don’t see it explicitly stated but I think the stronger the magnetic field the greater the saturation that can be achieved through hammering. Not necessarily up to 100% saturation though.
How exactly hammering works is still unclear to me. Apparently it is increasing energy in magnetic domains that allows them to change orientation but I have nothing more specific I can explain. If the level of saturation achieved through hammering does increase with a stronger magnetic field then the original question has one answer, an unsaturated magnet that was magnetized by hammering can be strengthened by hammering it again in a stronger magnet field than it was created with.
An unsaturated magnet can be increased in strength by stroking it with a second magnet. Here again there is the involvement of a physical force. It’s not clear what the relationship between the field strength of the second magnet is to the degree of strength achievable but it’s not clear to me that they are directly related because of all the possible ways physical size and magnetic domain density can vary. However, this method uses physical force to increase magnetic strength, not just letting a magnet sit in another magnetic field. It also appears to be another way to increase the strength of an unsaturated magnet.
Another method of increasing magnetic strength has been stated as leaving an unsaturated magnet in a stronger magnetic field. I don’t know what difference a stronger magnetic field makes because of the possible different sizes and magnetic domain densities. I’m not really clear why that would increase the strength of the magnet at all just sitting in the field. It is not like stroking or hammering that includes some physical force. What makes a little sense is that an unsaturated magnet can’t saturate itself, so it’s own magnetic field must have already aligned any unaligned magnetic domains that it can with it’s own field, and a stronger field is needed to align any more domains.
This leaves me with a lot questions. So far I am looking at magnets of the same general size, shape, and material, that would measure the same flux density. But suppose I put a physically small magnet between two larger ones. All measuring the same tesla, but the larger ones with more webers altogether. I have no idea if what difference that makes and there are other ways that magnetic flux measurements can be manipulated.
In conclusion, using hammering and stroking can increase the field strength of a magnet, to some degree, possibly to some high degree of saturation. It is not clear that stronger magnets have to be used, but the result may be limited. After that the magnets are limited by their size. Early generators were often very large because iron alloy magnets are relatively weak. Assuming reasonable limitation of the size and of a magnet generator made from limited materials it looks quite feasible to bootstrap generation of electricity, and stronger magnets as a result, with a magnet generator made from iron simple iron magnets. That might require a lot of large magnets and a rather large generator to get the process started.
