P
Paul Burridge
I imagine Kev's still awaiting a decent advance from Ladybird. ;->
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I imagine Kev's still awaiting a decent advance from Ladybird. ;->
P
Paul Burridge
And more specifically, the differences in phase of the voltage of the
signal at the same point on adjacent turns, presumably?
K
Kevin Aylward
Paul said:
Nope. Bantam paperbacks are my favourite. They done alright for Steven
Hawking.
Kevin Aylward
[email protected]
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
http://www.anasoft.co.uk/replicators/index.html
Understanding, is itself an emotion, i.e. a feeling.
Emotions or feelings can only be "understood" by
consciousness. "Understanding" consciousness can
therefore only be understood by consciousness itself,
therefore the "hard problem" of consciousness, is
intrinsically unsolvable.
Physics is proven incomplete, that is, no
understanding of the parts of a system can
explain all aspects of the whole of such system.
F
Fred Bloggs
Paul said:
This is actually the essential explanation for the capacitance-
apparently some people around here are oblivious to the fundamental fact
that there can be no voltage gradient in a perfect conductor. Resistance
implies finite conductivity and internal electric field gradient- and it
is the electric field gradient that establishes stored electric field
energy aka capacitance.
J
John Larkin
Of course there can. Just build a superconductive inductor or antenna.
John
D
Dave VanHorn
Of course there can. Just build a superconductive inductor or antenna.
Think again. A superconductor has no resistance, so how would that voltage
gradient form?
R=0 so the V*I drop is zero, no matter where you look.
Think again. A superconductor has no resistance, so how would that voltage
gradient form?
R=0 so the V*I drop is zero, no matter where you look.
J
John Larkin
Think. How can a superconductive magnet make a magnetic field if you
can never establish a potential across its leads? Ever hear of
conservation of energy? Or E = L * dI/dT?
Try a simple experiment: measure the resistance of a transformer's
primary. Now plug it into the wall. Explain why the circuit breaker
doesn't blow.
John
K
Keith R. Williams
LC transmission line?
L is non-zero.
B
Ben Bradley
In sci.electronics.design, John Larkin
And to reiterate/reword what others have said, if resistance is the
main thing causing voltage difference between turns, you're using the
inductor at too low a frequency and/or it's wound with wire of too
high a resistance (too small in diameter).
At DC...
And even a straight wire is an inductor. When you wind it into a
coil (helix or spiral), there is significant capacitance between
windings, creating a self-resonant frequency.
And to reiterate/reword what others have said, if resistance is the
main thing causing voltage difference between turns, you're using the
inductor at too low a frequency and/or it's wound with wire of too
high a resistance (too small in diameter).
At DC...
And even a straight wire is an inductor. When you wind it into a
coil (helix or spiral), there is significant capacitance between
windings, creating a self-resonant frequency.
D
Dave VanHorn
John Larkin said:
No problem at all. Current is supplied externally, energy is stored in the
magnetic field.
They do make superconducting electromagnets.
Superconductors have no resistance.
Therefore..
Don't let them warm up, while the current is circulating though.
Other than that the transformer is inductive, I can't imagine what you're
trying to prove here.
J
John Larkin
That there are ways you can put lots of voltage across a very small
resistance.
John
D
Dave VanHorn
Ah, I see.
No resistive drop, but until the current catches up, there's a voltage drop.
J
John Popelish
Dave said:Ah, I see.
No resistive drop, but until the current catches up, there's a voltage drop.
As long as the magnetic field around the wire is changing, the wire
will have an inductive voltage drop (by V=L*(di/dt). Also, if an
electromagnetic wave is following the wire, there will be peaks of
alternating voltage at 1/2 wavelength along the wire that follow the
wave (as the wave sloshes current from one bit of line capacitance to
the next bit through the line's inductance). If there are waves going
both ways (standing waves) there will be AC voltages of alternating
polarity at nodes 1/2 wavelength apart, but standing still.
Resistance is not needed to allow either of these mechanisms to
produce voltage differences at points along good (even perfect)
conductors. And those voltages drive charge through local
capacitances.
D
Dave VanHorn
Makes sense, and that lines up with the behaviour of a disc or ring of
superconductor, which is a shorted turn, and can't have that happen, so it
excludes the field, giving the messnier effect.
You know, superconductors are getting cheaper all the time..
I wonder what a 1M dia loop of superconductor, good for 10-20 A at 2-30 MHz,
would cost?
Bottle of liquid nitrogen..
J
John Larkin
It's cool that the prop velocity of an electrical signal traveling
down a bare wire is just coincidentally equal to the velocity of an EM
wave in free space. That's why a wire makes a good antenna.
Whoever designed this universe was one clever SOB.
John
K
Kevin Aylward
John said:
Its not a coincidence. Since *all* of EM phenomena can be attributed to
the momentum exchange of photons under QED it has to be that way. All EM
*is* photon motion.
See above
Kevin Aylward
[email protected]
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
http://www.anasoft.co.uk/replicators/index.html
Understanding, is itself an emotion, i.e. a feeling.
Emotions or feelings can only be "understood" by
consciousness. "Understanding" consciousness can
therefore only be understood by consciousness itself,
therefore the "hard problem" of consciousness, is
intrinsically unsolvable.
Physics is proven incomplete, that is, no
understanding of the parts of a system can
explain all aspects of the whole of such system.
F
Fred Bloggs
John said:
You are turning it into a distributed component, Bowick is mainly
concerned with lumped elements.
F
Fred Bloggs
Kevin said:
Yeah- that response is typical of your irrelevance- bring QED into
designing a dog-simple coil for 10MHz operation...
K
Kevin Aylward
Fred said:
Not irrelevant enough for you to ignore though.
Kevin Aylward
[email protected]
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
http://www.anasoft.co.uk/replicators/index.html
Understanding, is itself an emotion, i.e. a feeling.
Emotions or feelings can only be "understood" by
consciousness. "Understanding" consciousness can
therefore only be understood by consciousness itself,
therefore the "hard problem" of consciousness, is
intrinsically unsolvable.
Physics is proven incomplete, that is, no
understanding of the parts of a system can
explain all aspects of the whole of such system.
R
Reg Edwards
For given dimensions and number of turns on a single-layer solenoid
calculate all characteristics of interest, including stray capacitance and
self-resonant frequency.
Make yourselves familiar with the magnitudes involved.
Download self-contained program SOLNOID3 in a few seconds and run
immediately.
----
............................................................
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
............................................................
calculate all characteristics of interest, including stray capacitance and
self-resonant frequency.
Make yourselves familiar with the magnitudes involved.
Download self-contained program SOLNOID3 in a few seconds and run
immediately.
----
............................................................
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
............................................................
