Archive for February, 2016

electromagnetismYou may have heard someone state that electricity is just a form of magnetism or vice versa. Indeed, the two forces are deeply interrelated. Here’s a little information about that interrelation from someone who has no idea what they’re talking about:

To really understand the difference between magnetism and electricity, we may have to delve deeply into special relativity. More broadly, special relativity is the generally accepted theory regarding the relationship between space and time created by Einstein. His postulates are the following:

  1. that the laws of physics are invariant (i.e. identical) in all inertial systems (non-accelerating frames of reference) and
  2. that the speed of light in a vacuum is the same for all observers, regardless of the motion of the light source.

This relates to classical electromagnetism in that it begets formulas for how electromagnet objects, in particular the electric and magnetic fields, are altered under a Lorentz transformation from one inertial frame of reference to another.

The Lorentz transformation (or transformations) are coordinate transformations between two coordinate frames that move at constant velocity relative to each other. Frames of reference can be divided into two groups, inertial (i.e. relative motion with constant velocity) and non-inertial (accelerating in cursed paths, rotational motion with constant angular velocity, etc.). When you hear the term “Lorentz transformation”, think of transformations between inertial frames. Basically, Einstein’s theory of special relativity makes it possible to understand that the frame of reference ultimately determine if an observation follows electrostatic or magnetic laws.

Basically, if you look at a classical stationary electric charge, it creates a purely electrical field i.e. the Coulomb field. The Coulomb field is responsible for generating the phenomena of static electricity. However, if you then look at that electric charge from the standpoint of a reference frame which is moving with respect to it, the electric charge may now seem like it’s moving, i.e. it’s an electric current which in turn creates a magnetic field.

electromagnetism2So let’s bring it back to eye level: permanent magnets generate their magnetic field through two main mechanisms:

  1. the orbital motion of electrons around the nucleus. Electrons are negatively charged, making this equivalent to an electric current that creates a magnetic field.
  2. the spin off the electrons themselves. this again creates a magnetic field, so that the atoms behave like tiny magnets.

So now it’s time to talk about ferromagnetic materials. Ferromagnetic materials have subatomic properties that allow for the atoms that make them up to behave like the tiny magnets that they are and align their magnet’s directions together in local units called magnetic domains. This then creates a larger magnetic field.

It’s not enough to work as a battery, however. This is because the motion of the electric charge in the atoms is cyclical and the spin of the electron doesn’t move the charge from one place to another. For a battery, you’d need a movement of charge that results in separation of positive and negative charge, which then would be made available at the terminals. Permanent magnets can’t function as batteries because this isn’t how they work.