Magnet Myths and Misconceptions

[TinselKoala]

And what is a charge?

That which is moved by the field.

Charge, field, motion, one thing. One.


Now you might as well ask "what is matter" or "what does God really look like".

[TinselKoala]

And what is a charge?

Seriously? It is a fundamental property of matter, one of the "quantum numbers" that describes certain kinds of subatomic particles. It is a conserved quantity, just like momentum or energy. It is that property of matter that causes the associated particle to move in certain ways under certain conditions. It comes in two "polarities" that we arbitrarily call positive and negative. Charge is quantized, which means it comes in discrete amounts, the smallest of which is the Unit charge, and the electron is the particle which carries the Unit Negative Charge.

What is "wetness"?

[Pirate88179]

Bill,

Metals are good conductors because they exhibit free (loosely bound) electrons in their structure. Insulators don't have free electrons, so they are poor conductors of electricity.

See this pdf and this Hyperphysics page.

Just because the free electrons in a wire are constantly scattered and colliding as they make their way from one end to the other, doesn't mean the wire becomes worn out. For the electrons that do leave the wire, there are an equal number entering.

.99:

Thank you.  So, does this mean that the "charge" is like the example that MH gave of the Newton's ball arrangement then?  An electron enters the conductor and collides with (repels) one of those loose free electrons in the conductor and bumps it down along the conductor into other free electrons, etc, etc.  The Hyperphysics link described this as a chain reaction.  Your links, combined with MH's example now make this a lot more clear to me. 

Thank you very much both of you.  I am a lot closer to understanding what is really going on which, of course, could be dangerous.

Bill

[TinselKoala]

Bill,

Metals are good conductors because they exhibit free (loosely bound) electrons in their structure. Insulators don't have free electrons, so they are poor conductors of electricity.

See this pdf and this Hyperphysics page.

Just because the free electrons in a wire are constantly scattered and colliding as they make their way from one end to the other, doesn't mean the wire becomes worn out. For the electrons that do leave the wire, there are an equal number entering.

True enough... but....

http://en.wikipedia.org/wiki/Electromigration

[MileHigh]

Bill:

I can actually offer up a pet theory about your old wire story from the electricians.  I have not done any searching on this at all.  My pet theory is that it may be possible that the metal mixtures in some very old wire may be 'off' or the wire itself was poorly manufactured.  For example, when the metal was made into wire it was not a homogeneous mixture, or they used cheap and inferior copper with too many impurities, etc.

So over lots of time, say 50 years, some of the copper or aluminum atoms started to crystallize.  Or the impurities started to crystallize.  Atoms can actually slowly migrate through the metal over time to gather together.  That physical rearrangement of some of the atoms in the wire would cause micro-fissures or perhaps even very fine cracks visible under a microscope.  Or, the fact that the wire was partially crystallized means that the moment you handled it then fissures or cracks could happen.  The net result would be that the wire would be more resistive because the cracks would reduce the cross-sectional area in various places along the wire.  It's just a guess.

Bill/TK:

No, it was TK (I think) and others that suggested the "Newton's ball" model for current flow were "entering electrons" "push" against neighboring electrons to give you current flow because of the electrical repulsion between electrons.

I don't believe that model is correct.  What I stated is that all of the electrons in a wire will be induced to move at the same time because of the presence of an electric field in the wire,  The electric field snakes down the wire and induces all of the free electrons in the wire to move in unison.

So the electrons in the case of current flowing in a wire are not pushing against each other.  They are all just haplessly being pushed around at the same time by the presence of an electric field.

MileHigh