The Dark Side of Amateur Science by Bill Beaty

[realdt]

I am amazed about how much I have learned from you Mr. Beaty

[beatlegreg07]

amateur science - we do what we must because we can. but there's no point crying over every mistake, you just keep on trying till you run out of cake

[wbeaty]

The good stuff (physics demos) starts at 2:50

Visible electricity device, diamagnetic levitator, anomalous magnetic carbon

[abdelkarimhosni]

liar

[chrisofnottingham]

"Electric current is proportional to electron velocity"

This may be true but providing more voltage in a given conductor doesn't move them faster, it just moves more of them at the same velocity. You probably know this anyway but I don't think it helps to gloss over things like this.

[wbeaty]

@chrisofnottingham No, the resistance of the conductor, as well as its density of charge-carriers remains relatively constant. Different currents give different electron drift-velocities. E.g. at zero current, the average drift-velocity of electrons is zero. At low current, the drift velocity is low. (Note that electron's random thermal velocity is always there and is very large, and is not an electric current in a circuit.)

[chrisofnottingham]

@wbeaty It looks like you are correct.

One of my college teachers told us (as an aside, not part of the course) that the electric current drift velocity of free electrons is always the same in a conductor at the same temperature but that a higher voltage moves more electrons. This appears to be wrong.

Although I still have a tiny doubt because much of stuff I can find that is written down at my level talks about average velocity of all free electrons, which would be the same in either case.

[wbeaty]

@chrisofnottingham yeah, the RMS velocity of charge carriers basically IS the temperature of a metal. Amperes of drift-velocity has little impact. It's no big mystery: in dead calm air, the air molecules still are moving at hundreds of KPH. "Wind" is a globally-averaged macro motion. Draw your Gaussian surface at different size scales, and you get different results. In metals, electrons always have high velocity, even when there's 0 mA (zero average drift velocity) in the wire.

[blahdob]

and here's AC

WRWRWRWRWRWRWRWRRWWR

[wbeaty]

Square (cube) wheel, rolls smoothly: 1:48

"Visible electric currents" device 3:32

DC versus AC 4:33

Martin Simon's diamagnetic levitator toy 4:50

Pure spectroscope carbon rods. Carbon-arc debris is magnetic! Alchemy transmutations, iron particles? 6:14

[faro0485]

Is that it?