Electromagnetism via practical/theoretical

wolfric

I want to learn more about electromagnetism. I've tried 2 books so far but both laden with heavy maths. I don't mind the maths approach but it's just not what I'm looking for. I've already read through the wikipedia entry and some articles such as how stuff works.

What i'm not too sure on is how you would build something basic that generated electromagnetic waves and receive those waves on another device. How i would adjust the frequency and more on the theoretical part as well. I'm quite interested in the fact that it's able to convert from magnetic to electric and back over and over and how (i think) the electric waves happen at right angles to the magnetic ones.

When i think of electricity, i think of it in electrons which assumes it has mass but then how can it go from magnetic wave to electric.

I hope by some of these questions someone could recommend (preferably) a book or else if nothing fits, some articles.

FISMA

wolfric wrote: »

When i think of electricity, i think of it in electrons which assumes it has mass but then how can it go from magnetic wave to electric.

Wolfric,

Most people learn Mechanics, then some Thermo, E&M, and Optics, Modern, and so on.

Mechanics is easy to see in the real world. Cars speeding up, slowing down, planets, ice, friction. It is easy to make analogies in Mechanics when it comes to your every day world. That's why Mechanics is less troublesome to learn or teach.

E&M is another kettle of fish. Pointing out E&M in our daily lives is more abstract. It is all too often a mental exercise of mathematical abstractions.

A few points.

An electron has the property of charge. Around an electron is an Electric Field. Around a stationary electron there is no magnetic field.

Current, is charge in motion, like an electron in motion. We must be specific about motion.

A wire with no current has no magnetic field surrounding it.

When an electron is in motion on a wire with a constant speed, there is a constant magnetic field around that wire.

Hence, we say that around every current carrying wire there's a magnetic field.

This is easy to detect with a DC battery, some wire, and a compass. Don't try it on the household wires as they are Alternating Current - the current changes direction too fast for the compass to respond.

Now, let's change things up. Instead of an electron in motion with a constant velocity, let's accelerate it by speeding it up. Now we do not have a constant magnetic field, but an increasing or constantly changing magnetic field.

It's that changing magnetic field that is interesting, as it gives rise to a Electric field.

A changing magnetic field gives rise to an electric field. A changing electric field gives rise to a magnetic field.

That's Faraday's Law and Ampere Maxwell's Law.

Thus, an accelerating electron generates an electromagnetic field.

Let there be light .

If I were you I think I would post this on the Engineering board and try to get the help of an electrical engineer. You don't have to reinvent the wheel if you're only trying to understand how to use it.

Note: an electron going around a nucleus is accelerating - since it changes its direction. Thus, if it is giving off energy, shouldn't it be in a decaying orbit?

This was one of Bohr's concerns with the atom which is why he quantized the levels in which electrons could exist.

sponsoredwalk

Hey if you want to learn about this without too much mathematical strain
I would recommend the online video series "The Mechanical Universe".
Every episode is on google video &/or youtube. There are 52 half
hour lectures that go from basic mechanics up to all of E&M to special
relativity to some quantum mechanics.

The show does have a good bit of math but they explain it in such a
way as to be really understandable & if you get lost you can ignore the
math parts. They go really in depth, deriving things like the speed of light etc... wonderful stuff.

Here is a lecture on magnetism from the video series that you should
watch to see what it's like, if you think it's worth watching I'd recommend
going back to the start as they intersperse a lot of E&M with the other
lectures @ various times...

Here is where a lot of them are...

This series isn't too taxing & you really don't need to understand anything
in physics as long as you watch from the beginning, some hilarious
jokes in it too & the classroom shots are ridiculous :P

Edit: Yes there's some in depth analysis of electrons conducting electricity
in materials with 80's video animations of it all along with kinetic & potential
energy graphs too

Morbert

wolfric wrote: »

When i think of electricity, i think of it in electrons which assumes it has mass but then how can it go from magnetic wave to electric.

Electric fields and magnetic fields do not have independent existence. They are both parts of the same field. This field will exhibit different properties from different perspectives or 'coordinate systems'. So in one coordinate system you might see a stationary electron and a purely electric field. In another coordinate system, you might see the electron moving, and both an electric and magnetic field.

Also, it is important do differentiate between electricity and electric fields. Electricity is made of electrons, but to say electric fields are made of electrons would be like saying gravity is made of skydivers.