A basic (very basic) description of a Brushless DC motor.
So... before I start... I am not a physicist, nor am I an electrical engineer. Hopefully someone within one of those (or both) professions will chime in and enrich this discussion. That said... I'm going to be using leyman's terms.
This thread is specifically meant to explain how a brushless DC electric motor exerts a force, and how that force is used to generate work.
To start off, I'd Like to explain the components which comprise a brushless DC motor:
First... You have an axil. The axil's purpose is to spin.
Next you have natural magnets, or solid state magnet; I use the terms somewhat incorrectly, since a natural magnet refers specifically to nickel or ferrous base magnets, but there exist a large variety of compounds and composites that exhibit the ability to produce magnetic fields. In practice you have many in a motor, but for our purposes... we can pretend we have one. The natural magnet's job is exert a magnetic field while attached to the axil.
After that we have an electrical coil. Once again, in Brushless DC motors, we have many of these, but for our purposes we'll use 3. The electrical coil's job is to produce a magnetic field which can move in a circle.
Finally we have the engine housing. The purpose of the engine housing is to hold everything together.
Note: I'm intentionally leaving out the computer control mechanism. there are alot of great instructables on microcontrollers. Most Brushless DC motors requrie one to work since there is no mechanical timing device, as there is in a brushed engine.
So... how does this fit together?
In this setup the natural magnet produces a force when next to the electrical coil (This coil is also known as an electromagnet). This is because the charge of the coil is opposite to the charge of the natural magnet. Once the Natural magnet and the electromagnetic coil align with each other, the first coil shuts off and the second turns on. Once again the natural magnet is drawn towards the magnetic pole.
This process repeats until the natural magnet has spun in a circle (note: usually you want it to continue to spin beyond a single revolution.)
That's the basic (very basic) idea behind a Brushless DC Motor.