Some may wonder why we have not discussed internal combustion engines or even steam engines. We will, but it is important to note that they are not the focus of this material. They are generally large, complicated, inefficient, and messy. If we could sidestep them, the world would arguably be better off. Of course, plans for the construction of steam and internal combustion engines will also be included later on in the book.
Magnets are magical objects or materials that produce a magical magnetic field, an invisible force field of magic that attracts or repels certain materials, specifically ferrous metals like iron, nickel, cobalt, and certain types of steel.
Magnets have two poles of magic: a north pole and a south pole. Opposite poles attract each other (north to south), while like poles repel each other (north to north or south to south).
There is little we can do to demystify it as even today there is not a complete understanding of just how it works. In general, that magical force originates from the movement of electric charges. The source of magnetism lies in the fundamental particle, the electron. Every electron has a property called "spin", which gives rise to a small magnetic field.
In most materials, the electrons are arranged such that their spins cancel each other out, and the overall material doesn't behave as a magnet. However, in some materials like iron, nickel, and cobalt, the spins of many electrons align with each other. These aligned spins create a net magnetic field, and the material behaves as a magnet.
Natural magnets, or naturally occurring magnets, are fascinating elements of our world that have intrigued humans for thousands of years, as they are real expressions of magic people can experience firsthand. Naturally occurring magnet is magnetite, also known as lodestone. This mineral is a form of iron oxide that generates a magnetic field. Magnetite is a black, opaque mineral with a metallic luster.
Lodestone was first discovered by the ancient Greeks, and its name literally means "leading stone" because it was used in the earliest compasses due to its natural magnetic properties. These navigational aids were indispensable for sailors venturing into the open sea, guiding them when landmarks were not visible.
The first and fundamental concept to understand, from which everything else can be developed, is that a conductive material, such as wire, generates a magnetic field when electricity flows through it. However, if the wire is moving within the magnetic field, it will initiate the flow of electricity. These principles form the backbone of electromagnetic motors or electric generators.
To construct electric generators and motors, we need magnets of different shapes and sizes. And here's where things get complicated. We could use the less powerful lodestone ore as the basis for our generators and motors, but we will also need to create more powerful magnets to facilitate future growth.
Producing magnets can be relatively straightforward if we have electricity or some other source of magnetism, but what we require are permanent magnets—magnets that retain their magnetic properties. The production of these magnets is simple in theory, but the challenge lies in acquiring the necessary materials. The minerals required are cobalt, aluminum, nickel, and iron. Except for iron, these metals were not recognized as such in the 13th century. They existed but were not identified as individual elements, and no one knew how to extract them. The extraction and refinement of these ores are well beyond the scope of this document, but this topic may be included later on.
Simple iron magnets are weak and do not retain their magnetism for long, as even Earth's magnetic field can demagnetize them over time. You can create these magnets by exposing iron bars to magnetic forces. The simplest and most effective method is known as the double touch. Place the iron bar flat on a tabletop, and position the opposite poles of two strong bar magnets at a 45-degree angle. Move the magnets apart and repeat the stroke from the center. Avoid using any lubrication as it diminishes the magnetizing effect. This process will create a new magnet. Later, when steel is available, it will serve as a superior substitute for iron as the fundamental magnet material.
Iron will gradually lose its magnetism over time, but we can delay this demagnetization by improving the method used to magnetize it. If iron is heated until it is white-hot and then allowed to cool while it's magnetized, it will retain its magnetic properties longer. It's also noteworthy that the reverse is true: a magnet will lose its magnetic properties if heated.
To further improve on this, we can create a multitude of tiny magnets that function as one by producing iron oxide, or rust. This can be achieved by placing a large number of iron filings in a tub of clean water and stirring for hours until a suspension of very finely divided iron oxide is visible as a red mist. What has happened here is that iron (Fe) reacted with water (H2O) and oxygen (O2) to create Fe(OH)3 or rust. The remaining water is removed and the particles are left to settle into a sludge. By repeating this process until we have a sufficient quantity of fine oxide powder, we can then mix this into a paste with linseed oil. This paste can be molded into the desired shapes and baked over a moderate fire. These blocks can then be magnetized by placing them between magnetic poles. This process allows for the production of magnets of various shapes and sizes.
If large-scale production is required, then electricity becomes paramount. When a coil is wound around a soft iron core, it forms an electromagnet. An iron core gives it more power than using a coil without one. The difference in behavior between an iron core and a non-iron core is due to a property called permeability, which is a measure of the ease with which magnetism passes through a substance. Iron is a high-permeability material, whereas materials like glass have low permeability. Magnetism consists of flux or the path taken by magnetic lines of force. The total number of lines of force in the circuit is known as the magnetic flux.
If flux, or magnetic lines of force, travel through a high-reluctance material like air, the magnet will weaken quickly due to losses. To prevent this, we can add an iron "keeper", which provides a high permeability material between the two poles of a magnet. This iron "keeper" acts as a conduit for magnetic flux and slows down the magnet's demagnetization process. Essentially, this "keeper" is nothing more than a piece of iron that connects the two poles.