What do we know about magnetism, really? It’s kind of a mysterious force. The earth is a giant permanent magnet. The magnetosphere protects us from cosmic radiation and intense ultraviolet rays that would strip the oxygen from our atmosphere.
Any iron object can be made into a permanent magnet by holding it parallel to the earth’s magnetic field and hitting it with a hammer. The impact causes some of the iron atoms to align with the magnetic field and your iron is magnetized.
This won’t make a very “good” magnet, not very strong, but it demonstrates the idea. The needle of a compass is slightly magnetized to show the lines of the earth’s magnetic field. Navigation on land and sea since the 11th century has been enabled in part by the humble compass.
When Faraday discovered that electric charge in a conductor produced a magnetic field, his discovery led to the creation of the first electric motor in 1821. The Faraday motor was mostly a demonstration of a major principle in the nascent field of electromagnetism. 75 years of improvements and the widespread availability of electricity made the electric motor the logical replacement for the steam engine as the work horse of industry.
We create permanent magnets by concentrating the energy of an electromagnet onto a magnetic alloy and assemble, for example, small alnico magnets in small dc brush motors to power electric screwdrivers. There are 2 motors in any air conditioning unit, and if it’s central air, they can be the largest loads in your home. There may be dozens of motors in your home, another dozen motors in your car; starter motor, wind shield wiper motor, motors for air conditioning, power windows, fuel pump, all kinds of things.
As an economic activity, the US builds and ships about $12 billion worth of electric motors in a wide variety of shapes and sizes.
Extreme requirements like the multi-megawatt generators used in horizontal wind turbines push the envelope and motor designers are constantly coming up with new configurations to solve a variety of design constraints.. The wind market is exploding with small wind machines and experimental generator designs. Among the home brewed designs are many versions of the axial flux type since they appear to be fairly easy to build. Unfortunately, the axial flux motor is very inefficient which can be a limiting issue for folks experimenting in this area.
On one hand the electric motor is still somewhat mysterious, and yet, like many aspects of modern technology, we have figured out the rules required to create reliable, high performing machines. Modern automation, robotics, air conditioning, electric cars would all be impossible without a working knowledge of magnetics.