Tesla and wireless power

[Rich Grise, Plainclothes Hippie]

I was just musing the other night about Tesla's AC and how it
revolutionized electric wiring, with the step-up transformers and
all.

Well, if you start with, say, 100V, you need to carry 1 amp to power
a 100W light bulb.

But if you step up the 100V to 1,000V, you only need wire that can carry
100mA.

And if you step it up to 1,000,000V, you only need 100 _micro_ amps.

So, logically, if you could step up the voltage enough, you shouldn't
need any wires at all!

Unfortunately, the darned electrons arc over to stuff before they get
to the destination transformer. )-;

But, in fairness, those guys were just discovering electricity for the
first time, and NOBODY knew anything about how it might behave.

Thanks,
Rich

 

[Tim Williams]

And if you step it up to 1,000,000V, you only need 100 _micro_ amps.

Of course, you get more than 100uA to the surroundings through capacitance
alone (just at LF), and you get capacitive dividers everywhere. Even
without Hertzian waves (negligible for 25/50/60Hz), you lose voltage
everywhere.

So, logically, if you could step up the voltage enough, you shouldn't
need any wires at all!

So logically, if you could step up the voltage sufficiently, you could
lose voltage everywhere.

But, in fairness, those guys were just discovering electricity for the
first time, and NOBODY knew anything about how it might behave.

Tesla seemed to have a pretty good idea, except for the appreciation of
resonant loss.

His works suggest that you can keep adding energy to a resonant system and
it will stay there forever. In reality, a constant amount of power is
required. This is why you can't shake a house to pieces with a fist-sized
motor, it's too lossy.

Tim

 

[Paul Keinanen]

I was just musing the other night about Tesla's AC and how it
revolutionized electric wiring, with the step-up transformers and
all.

Well, if you start with, say, 100V, you need to carry 1 amp to power
a 100W light bulb.

But if you step up the 100V to 1,000V, you only need wire that can carry
100mA.

And if you step it up to 1,000,000V, you only need 100 _micro_ amps.

So, logically, if you could step up the voltage enough, you shouldn't
need any wires at all!

Unfortunately, the darned electrons arc over to stuff before they get
to the destination transformer. )-;

The G-line http://en.wikipedia.org/wiki/Goubou_line could be used to
direct the RF energy to the place wanted .

 

[PeterD]

I was just musing the other night about Tesla's AC and how it
revolutionized electric wiring, with the step-up transformers and
all.

Well, if you start with, say, 100V, you need to carry 1 amp to power
a 100W light bulb.

But if you step up the 100V to 1,000V, you only need wire that can carry
100mA.

And if you step it up to 1,000,000V, you only need 100 _micro_ amps.

So, logically, if you could step up the voltage enough, you shouldn't
need any wires at all!

Take a minute. Divide it in half. Divide the remaining part in half.
Continue forever, and the minute never ends, right? Same (mis)
logic... So we have beat both power transmission and time!

Unfortunately, the darned electrons arc over to stuff before they get
to the destination transformer. )-;

What's a few sparks... I just hate it when my clothes stick to me,
along with every bit of fuzz and lint in the room. And you should see
the cat's reaction when I tried it--she freaked out.

But, in fairness, those guys were just discovering electricity for the
first time, and NOBODY knew anything about how it might behave.

Yea, but some day we'll figure it out!

What I want is unified connectors: power, signal and control in one
(standard AC three pin) connector. TV: plug it in and it works. Phone?
Plug it in and it works. Computer: Plug it in and it works!

 

[[email protected]]

Tesla had an excellent excuse, but the modern Tesla enthusiasts don't.

Why? Both were/are mad. ;-)

 

[Grant]

Tesla had an excellent excuse, but the modern Tesla enthusiasts don't.

But they seem to take so much care in winding that tall secondary,
they look quite pretty, that shiny enamelled wire cylinder. Quite
useless, except for the Buzzt! factor long sparks

 

[Grant]

I'm not talking about Tesla _coil_ enthusiasts. They're obviously doing
worthwhile stuff--I mean, making 20-foot sparks is at least as useful as
blowing up anthills with dynamite, for instance. Blowing up stuff is a
logical consequence of having testosterone, it's fun, and it's
occasionally a life saver.

It's the wireless power transmission / over unity / extracting
continuous power from permanent magnets / loony types I'm fed up with.

Reminds of a problem a friend posed recently, if one gets a large
strong rare earth magnet, and hangs a heavy weight from it to a
steel beam in the shed, what's doing the work of the magnet holding
up that weight? Wont the magnet 'wear' out?


Related, ever had an MRI? They put you in a big magnetic field, then
they modulate that field to 'somehow' get images... Sound like a
jackhammer, the operator side, they gave me headphones playing music
to hide the noise (no metal in them, headphones had plastic tubes).

This thing was built big, solid, one could feel, hear the energy
thumping around. Remove all metal objects from pockets quite some
distance from the room with the magnet.

Grant.

 

[Grant]

Work is force times distance. Since the weight isn't moving, no power
is required. If it does come loose, the weight as it falls will do work
on the magnetic field, in such a way as to account for the extra field
energy of the magnet in air vs. in contact with steel, plus a bit extra
for the eddy currents.

Ever notice that nobody asks these questions about the electrostatic
force, which is what holds solids together, including the beam, the
weight, and the magnet? If the rope breaks, nobody wonders about the
work done on the electrostatic field in the process, though it's
mathematically similar and conceptually almost identical.

People have this idea that magnetism is somehow magical and mysterious,
whereas it's been a matter for calculation and not speculation for over
150 years. It is cool and sometimes counterintuitive, but not
mysterious. That's where the Tesla types go wrong. Not everyone knows
that sort of math, of course, but it's all the sturdy 18th and 19th
Century type, not this newfangled stuff. Most folks could learn it in a
year or two if they wanted to make the effort, but of course it's way
easier to produce reams of blather on the Net instead.


Yup. NMR systems for research often have glass helium dewars inside
there, so that a steel bolt flying into the magnet can make a _big_ mess.


Cheers

Phil Hobbs

 

[Grant]

[snip]

Reminds of a problem a friend posed recently, if one gets a large
strong rare earth magnet, and hangs a heavy weight from it to a
steel beam in the shed, what's doing the work of the magnet holding
up that weight? Wont the magnet 'wear' out?


Related, ever had an MRI? They put you in a big magnetic field, then
they modulate that field to 'somehow' get images... Sound like a
jackhammer, the operator side, they gave me headphones playing music
to hide the noise (no metal in them, headphones had plastic tubes).

This thing was built big, solid, one could feel, hear the energy
thumping around. Remove all metal objects from pockets quite some
distance from the room with the magnet.

Grant.

Yep. The only time I've come close to claustrophobia :-(

A friend reports the same, she needs to be sedated to go in there
again. I was only in up to my knees I've been in the tunnel
of a CAT scan machine, no jackhammers there...

Grant.

 

[[email protected]]

[snip]



Reminds of a problem a friend posed recently, if one gets a large
strong rare earth magnet, and hangs a heavy weight from it to a
steel beam in the shed, what's doing the work of the magnet holding
up that weight? Wont the magnet 'wear' out?


Related, ever had an MRI? They put you in a big magnetic field, then
they modulate that field to 'somehow' get images... Sound like a
jackhammer, the operator side, they gave me headphones playing music
to hide the noise (no metal in them, headphones had plastic tubes).

This thing was built big, solid, one could feel, hear the energy
thumping around. Remove all metal objects from pockets quite some
distance from the room with the magnet.

Grant.


Yep. The only time I've come close to claustrophobia :-(

A friend reports the same, she needs to be sedated to go in there
again. I was only in up to my knees I've been in the tunnel
of a CAT scan machine, no jackhammers there...

Grant.

...Jim Thompson

I thought I didn't need the earphones... never again will I make that
mistake :-(

Surprisingly, I didn't have any issues with claustrophobia and I generally get
quite nervous in confined places. It was cold and the ventilation was quite
good so perhaps my claustrophobia triggers weren't pulled. I didn't think the
sound was all that bad, either. Weird, but not unbearable. If the operator
weren't constantly trying to keep me calm I probably would have gone to sleep,
since I got about zero sleep in the three nights I was there (two in a room,
separate nurses with different schedules and a roomie watching TV all night).

 

[Fred Abse]

Reminds of a problem a friend posed recently, if one gets a large
strong rare earth magnet, and hangs a heavy weight from it to a
steel beam in the shed, what's doing the work of the magnet holding
up that weight? Wont the magnet 'wear' out?

Work is force * distance. If the weight is stationary, no work is being
done.

 

[Grant]

Work is force * distance. If the weight is stationary, no work is being
done.

Yes but if it was a pole holding up the weight, removing the pole would
allow weight to fall, so resisting gravity is not work? Helicopters
work very hard to hover in the air?

So weight on a pole is potential energy, waiting to fall, like water in
a dam... I guess I'm trying to explain it takes effort to resist gravity,
the magnet does that, like a dam, but not like a helicopter hovering.

Grant.

 

[Tim Williams]

Yes but if it was a pole holding up the weight, removing the pole would
allow weight to fall, so resisting gravity is not work? Helicopters
work very hard to hover in the air?

So weight on a pole is potential energy, waiting to fall, like water in
a dam... I guess I'm trying to explain it takes effort to resist
gravity,
the magnet does that, like a dam, but not like a helicopter hovering.

Your fallacy is in thinking it takes power to generate force, even though
Newton's law clearly states P = F*v. This fallacy arises by experience,
because muscles require power to generate a force. Columns and beams and
rocks clearly don't have to produce power to bear a load, proving Newton's
observations.

The reason aircraft must use power to generate force is because they
produce force against an unconfined fluid medium, something that can only
be done statically in one way.* The medium squishes out from under it, so
it has to constantly tread fluid to stay up.

*If the density is variable, you can float a blimp. Gravity produces a
density gradient, pulling more air to the 'bottom', so you just need
something lighter than air to take advantage of that difference.
Fortunately, we need lift to counter gravity, so blimps and planes go with
gravity quite naturally. If we didn't have gravity (but had atmosphere
somehow), blimps would not be possible, and planes would be unnecessary.

Tim

 

[ehsjr]

It's the wireless power transmission / over unity / extracting
continuous power from permanent magnets / loony types I'm fed up with.

They have this circular pipe that they painted the word "dream" on.
Put a bunch of magnets all around it, in *just* the right places,
and a ball bearing will travel round and round inside it forever.
The sound made by the ball bearing generates an electric current
in a transducer near the plane of the pipe "dream". The assembly
works great, when there are no pertinent facts nearby.

Ed

 

[Rich Grise, Plainclothes Hippie]

Reminds of a problem a friend posed recently, if one gets a large
strong rare earth magnet, and hangs a heavy weight from it to a
steel beam in the shed, what's doing the work of the magnet holding
up that weight? Wont the magnet 'wear' out?

There's no work done, because even though there's force, there's no motion.

And I was surprised that there was a thing called a "keeper" that you
could stick to your horseshoe magnet - as if shorting the "magnetic
circuit" actually helped maintain the field!

Thanks,
Rich

 

[Tim Williams]

It does. Crappy magnets gradually decay with time, due to the motion of
magnetic domain walls. The keeper reduces the magnetic field gradient
at the surface of the magnet, resulting in less driving force for the
domain wall motion.

Or from another point of view, it keeps the magnet biased with
self-magnetization. Old magnets, like alnico, had a soft B-H curve, not
nearly as square as later SmCo or NdFeB magnets. Alnico has a fairly
impressive Bmax of 1.2T (typical of steel alloys and comparable to NdFeB's
1.5T), but it drops off to about 0.8T at 0 A/m. This is also why alnico
magnets "burn in" with use (if anyone is old enough to have used new
magnets..), and are easy to demagnetize when overdriven.

Tim

 

[JosephKK]

Work is force * distance. If the weight is stationary, no work is being
done.

Fred, please remember to use the proper dot product notation. In
early grade school, kids often learn the scalar product thing that is
just plain non-physical; not even Newton used it. It leads to endless
errors that are hard to un-teach.

 

[JosephKK]

Your fallacy is in thinking it takes power to generate force, even though
Newton's law clearly states P = F*v. This fallacy arises by experience,
because muscles require power to generate a force. Columns and beams and
rocks clearly don't have to produce power to bear a load, proving Newton's
observations.

The reason aircraft must use power to generate force is because they
produce force against an unconfined fluid medium, something that can only
be done statically in one way.* The medium squishes out from under it, so
it has to constantly tread fluid to stay up.

*If the density is variable, you can float a blimp. Gravity produces a
density gradient, pulling more air to the 'bottom', so you just need
something lighter than air to take advantage of that difference.
Fortunately, we need lift to counter gravity, so blimps and planes go with
gravity quite naturally. If we didn't have gravity (but had atmosphere
somehow), blimps would not be possible, and planes would be unnecessary.

Tim

For some unusual fun play with the physics of the gas torus and "smoke
ring" of "Integral Trees" by Larry Niven.

 

[JosephKK]

Or from another point of view, it keeps the magnet biased with
self-magnetization. Old magnets, like alnico, had a soft B-H curve, not
nearly as square as later SmCo or NdFeB magnets. Alnico has a fairly
impressive Bmax of 1.2T (typical of steel alloys and comparable to NdFeB's
1.5T), but it drops off to about 0.8T at 0 A/m. This is also why alnico
magnets "burn in" with use (if anyone is old enough to have used new
magnets..), and are easy to demagnetize when overdriven.

Tim

Thanks, that made the connection for some of the odd structures i have
seen with early magnetrons and such.