Magnet Myths and Misconceptions

[TinselKoala]

Well this is electrostatic induction. So in the ball we have movement of charges or not.
The ball is an AC current.

But the Dirod generator is strictly a DC machine. One side is positively charged, the other side negatively charged. How can there be an AC current coming from a DC generator?

(This is a discussion question, not a position statement!)

[TinselKoala]

So we have a wire conected across a battery. What is the polarity of the magnetic field produced around the wire ?. Dose it change from one end to the other-from positive side of the battery to the negative side. Or do we have a monopole field?. If a magnetic field is built around the wire,what is going on inside the battery as far as a magnetic field is concerned?. Would we have one field being formed around the outer steel casing of the battery(normally the negative),and the opposite field polarity on the carbon inner rod of the battery(normally the positive)?.

The magnetic field produced by a current-carrying wire is _around_ the wire and you can visualize it as circular loops of field. Polarity is "direction" of the loops, there aren't really "N" and "S" poles to a circular field line or the field itself. The conventional direction of electricity flow is from the positive pole of the source to the negative pole. So if you point your right thumb in this direction along the wire and curl your fingers around the wire, the fingers will be describing the "direction" of the magnetic field around the wire. And you can demonstrate this with a magnetic compass. Believe it or not, for at least 20 years after electricity was being demonstrated in the laboratory, people did not understand that there was a magnetic field associated with current-carrying wires. The story is that it was actually discovered by accident during a classroom demonstration intended to prove that there was NO field around the wire, by Oersted in 1820.
http://en.wikipedia.org/wiki/Hans_Christian_%C3%98rsted#Electromagnetism
Inside the battery, there is a lot of electrochemistry happening and there isn't really a large coherent region where electron current flows. If you had small enough and sensitive enough instruments you could find net magnetic fields inside batteries, but you can demonstrate for yourself that batteries and ordinary magnetic fields don't interact much, by bringing a strong magnet near to a battery that is powering something.

"Dose it change from one end to the other-from positive side of the battery to the negative side. Or do we have a monopole field?" Neither one. The field is constant all along the wire and there is no such thing as a "monopole" magnetic field. You can arrange magnets, as in Halbach arrays, so that you only _see_ one polarity outside the bulk structure, but you can be assured that every field line emitted by the thing is in fact a closed loop that has no terminations. DivB=0.

Now it should be plain that if you have a field that is like onion skin shells around the straight wire, if you coil the wire into a solenoidal coil, the "shells" reinforce and add, and you now get a structure that makes "poles", where one end of the solenoid has a lot of field line "directions" coming out, and the other  end has field line "directions" that go in, and they loop completely through and around the whole solenoid. Again, the in and out are conventions, nothing is really flowing along the "lines of flux" of a magnetic field, unless you put it there.

[TinselKoala]

Awesome build

Thanks, I am especially proud of this unit. Unfortunately it is in limbo, in storage in Canada along with a bunch of other really neat stuff that I'll probably never see again.

[sparks]

    Does induction involve conversion of the kinetic energy of the conductor free electrons from random motion to orderly motion? 

[allcanadian]

@TK

So your textbooks are right: the formulae and all the rest of electrical
engineering math is stuck with Franklin's conventional flow of "electricity"
fluid from Positive to Negative. The Anode is the arrow -> pointing from the
more positive polarity to the more negative (or less positive, same thing). It's
a convention, that's all, like driving on the left side of the road in the
UK.

And the present understanding is also right: the actual flow of
charge goes from Negative to Positive. But so what? The math is based on the
other side of the convention, they are just words. There is nothing inherently
"negative" or "positive" about electrons, protons and charge! Franklin could
just as well have called them Male and Female, as he felt that there were indeed
two fluids involved in his concept of electricity.

I started using electron flow notation exclusively about 15 years ago when my primary area of research was electrostatics, personally I find it easier.
A simple analogy may be to see conductors as a basket of apples and oranges, if there an equal number of apples and oranges the charge is neutral. If there are more apples then the basket has an apple charge and if the there are less apples then there must be more oranges and the basket has an orange charge. When we move the apples to and from the basket then this motion of the apples is called an electric current.
Apples are electrons oranges protons.
We could also say if the apples are moving it is an electric current of apples and if the oranges are moving so must the basket or conductor of apples.
We say this because the protons are bound to electrons in the material of the conductor and must move with it. On the other hand the free electrons may move within the material producing a charge separation in objects or produce a net charge if an alternative path is present and this motion is called an electric current.
It is funny that something so simple could cause so much confusion which is why I believe the basics are so important. I think understanding the basics may lead to more questions and these questions answers.
As such we could say most of our technology is nothing more than a basket of fruit, apples and oranges, we pump out apples into a loop or circuit only to have the same apples return to the same basket. Apples and oranges are not Energy, the pumping action which caused the apples to move is work and the motion of the apples Energy. Now if we could just find some apples which refused to stop moving our troubles would be over, lol.
I think it's kind of neat how a small change in context can produce a large change in our perception of things and how they work.

AC