Can an Inductor Be Spherical?

Think you need to explain a bit more. Do you mean "wound on a spherical core/former" (just as a toroidal inductor is wound on a toroidal core), or some other arrangement?

Joe, John is right, much more information is required as to form factor, direction of winding, how it's wound, etc. The waveform (excitation) doesn't matter since inductance is a physical property of the inductor (time is not part of the equation) while impedance (which does have time in its units) will vary.

It's either have converging or diverging effect, just a free guess not much effort.It all depends where the terminals are wired.

Please explain "converging or diverging effect" in the context of an inductor. Even a straight piece of wire has inductance.

Just imagine if a current will pass through a sphere (either a solid or one in which has interior cavity-which have different effect than that of a solid) from then on, you have your implications already.

I throw a wild guess. Would it be a must to explain?

It would be helpful, as I don't have a clue as to what you're on about. Not for the first time, either.

Yes, especially since your premise is wrong, the interior-fill places no part in calculating the inductance.

Do you know the electromagnetic characteristic trace for that geometry(both solid and shell sphere). You may use it for the analogy of the inductance. Like what's the reason inductors in a pcb is made of just coiled conductor?

I meant to describe a sphere with wire wrapped around it (if possible) in such a way as to be both random and evenly distributed. But that also brings up some other special considerations to think about.

I'm guessing that cancellation will be one of the answers. But I was curious as to how a magnetic bottle would be created. Perhaps a temporary mono-pole? I simply struggle to think in 3D.

Hollow or solid doesn't make a difference to the inductance, it will affect the DC resistance, not much difference to AC resistance because of the skin effect.

Hollow or solid spherical core material will only effect how easily the core saturates.

Getting back to the initial question, an inductor can be made with spherical core material but it is a geometry that makes it harder instead of easier to fabricate. The geometry also makes it easier to misalign the coil winding to cancel instead of increase the magnetic field produced outside of the wires. This will have the effect of lowering the inductance while the added wire series resistance still gets added.

To sum it up, yes it can be done but you will just be making things hard on yourself.

Good answer! Precisely what I was looking for. Now that those brain cells of mine have been stimulated, I suddenly feel hungry!

YIG (yttruim-iron-garnet) spheres have been used in HP/Agilent/Keysight spectrum analyzers since the 1970s in gigahertz oscillators as the local oscillator. See here

gigahertz?

Isn't that leaving the part of the EM spectrum we call 'electricity' or 'radio waves' and moving into the area we call 'light'?

--edit--

Okay' it's just below what we call 'light.' Still, at that high of a frequency, you can use solid balls as inductors since the power is'nt traveling THROUGH the ball, it's jogging (sprinting?) on the SKIN.

Give me break, I'm talking 3-4 GHz (microwaves). Visible light is around 500 Terrahertz. On the other hand, I have an LED that produces light.

You didn't specify LOW gigahertz, and Tera- is the next 'level' up from Giga-, so it doesn't seem like such a big leap from one to the other.

You meant Henrys, not Farads, right?

Correct, I turned left when I should have turned right, or is it the other way around? Been a while since I've done analog electronics at the component level, I forget what leads or lags what by 90 degrees with caps and coils.

You might have better luck tying the wire in a "monkey fist" and nesting the {hollow} sphere within that, unfortunately, there will be wires going every direction, so I have no idea what the field will look like. OR you might try making a phoney "monkey fist" knot with three separate conductors, and choose (carefully) the direction of current to be necessary in each. What you end up with is a sphere approximately covered in coils in each direction, x, y, and z such that field could be switch reasonably quickly in any axis or linear combination thereof.

Surely you know how to tie a "monkey fist"!

It can be any shape, but some shapes are smarter/stupider than others.

For instance, a small stellated dodecahedron would be a poor inductor, albeit a good cocklebur.

I'm not sure that I understand what you mean by "star shaped" or stellated. I suppose that it is possible to wind wire around a sphere in a variety of geometries. And I realize that some methods may produce a useless device. Then again, it may be useless for AC but something completely different for DC or the other way around. I know it is probably way above my pay grade or worse, but I am just curious.

If it's classified, I'll just let it go. I'm just trying to climb back in the box.

Well, DC sees inductors as just very low-ohm resistors, unless your trying to shove a step function into them, where they will resist the sudden change, appearing as an immediate high resistance that drops as the coils saturate.

Remember, capacitors resist a change in VOLTAGE, inductors resist a change in CURRENT. That is why you never yank an inductor out of a live circuit, if it's got one milliamp running though it, and it suddenly 'sees' infinite resistance between its leads, it will 'try to maintain the current.' Ohms Law: V=IR. 1 mA * Infinite resistance = Infinite voltage. Or in other words, a nasty shock that will have you shouting the words your mother never wanted to hear out of your mouth.

Just *visualize* the magnetic lines eminating from/into our *spherical* earth in both dimensions, E and H fields.

No, that is a rotating sphere and it mimics a bar magnet. That is not the same thing.

Although this is unrelated, consider the drawings, or vitalizations of a "black hole". Every time I have seen that, it has been illustrated as the event horizon with stuff in orbit in roughly a plane around the black hole. But that is not the reality. Actual observations reveal that several suns orbit our galactic black hole in orbits that vary in size, speed, angle of the plane (relative to the plane of the galaxy).

Speaking only for myself, I don't like mis-direction for the sake of simplicity.

You're living on one.

Not what I described!

How not, in reply to your original post? The electrical currents flowing in Earth's interior act just like the turns in an inductor. That the interior is molten is irrelevant. All that matters is that it can - and does -carry a current, and an AC one at that; one whose period is measured in tens of millennia.

I don't know about inductance, but I've got a fair idea what would happen if you shot it from a length of rubber tubing stretched 50% of its length with 50 pounds of force.

You mean with a steel ball where the steel is conducting and the ball is a sphere?

Yes! As I said, I realize that it sounds a bit like nonsense. And I expect there is more than one answer highly dependent on how it is wound. I only ask because I could not find any information as to what characteristics it might have. If it were to cancel out all reactance, for instance, then it could only be a resistive device.

As to whether or not it would be useful, I suppose that would require knowing how it acts when connected to an external power source.

Some people say that everything has already been invented. A few people also said that in the 1930's but they were proven wrong. I am just resisting the urge to brush up on my rather dusty knowledge of electromagnetics. You might say that I am trying to conserve energy, uh... my energy! Those particular brain cells have not been disturbed in quite some time now, and I figured that as usual, I'm not the first person to ask such a question.

Priceless!

Lyn rocks!

Can an Inductor Be Spherical?

No, if what you mean is the flux radiating outward from the center. Magnetic flux must flow in loops (which is why it's called flux ). It has to get back from the outside to the center. There's no way it can do that unless it can get through the 4th dimension. AC or DC, it's still got to be continuous loops.

A spherical capacitor, on the other hand, is no problem. The earth is one, with the ionosphere charged up by electrical storms.

Wouldn't an isotropic antenna, if we could make one, be considered a spherical inductor?

I guess if it met the criteria for its being an inductor. Storing energy in a magnetic field, presumably one that sticks around instead of radiating away with its companion electric field, is one criterion that would be very hard for an antenna to meet for a DC magnetic field. I suspect antennas make better capacitors in this respect, but not very good inductors once everything settles down.

"Wouldn't an isotropic antenna, if we could make one, be considered a spherical inductor? "
Arguably, YES. See Figure 6.5 of this antenna treatise:
http://arlassociates.net/validationwheelerformulas.pdf
Mark Bingham
Relativity PL

You can't make an isotropic antenna either. Electromagnetic radiation is transverse, meaning that the oscillating electric and magnetic fields are perpendicular to the direction of propagation. It is for the same reason that somewhere on earth, the wind is not blowing, also known as the hairy ball theorem.

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

A longitudinal wave such as sound is a different story. There is no reason why a pulsating ball cannot emit sound isotropically.

"You can't make an isotropic antenna either."
Chu (the classic paper of 1948) and later McLean
http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=496253&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel4%2F8%2F10599%2F00496253.pdf%3Farnumber%3D496253
argue that an infinitesimally small dipole qualifies.Yes, I understand that one cannot build something that is infinitesimally small, but obviously the smaller the dipole the less the anisotropy.

Antennas are fine for the purpose, but not as an inductor as they do not storage energy in magnetic fields at zero Hz. Inductors do. At zero Hz an antenna acts as a capacitor.

I'm now sorry I brought at all the idea of the isotropic antenna to this discussion. When I started this now sorry tangent I announced that the isotropic antenna cannot be made. Then every Tom, Dick and Solomon jump all over it saying that it cannot be made. Now there is this silly comment that an antenna acts only like a capacitor. The blinders and gibberish shouting down the rational thoughts is too much for me.

I'm sorry you feel that way, but the scope of the question includes DC. If an antenna does not act like a capacitor at DC then what does it act like? Certainly not an inductor - unless it's a loop antenna

Blinders and gibberish shouting down the rational thoughts? Well, it's certainly heartwarming to know that your comments here are the only ones worth considering, yes? Doesn't make for much of a discussion but, hey, when you got it, flaunt it.

Bring on the OTs. I really couldn't care less.

Wow, now that is some "hairy" math! I can see that having some useful applications, such as charge transport on a spherical carbon spherule, although since I am having problems with the maths, and a spherule is not a perfect n-sphere (for that matter neither is a coconut), I still suspect there will be a zero point on that carbon spherule somewhere, and this could apparently present as a charge imbalance, possibly helping that sphere to rotate as it translates in an E-field. (this is only of local interest to me).

No idea, but a friend on mine who is a ham radio operator was telling me the other day about a new antenna design he is working on that relies on M-field projection rather than E-field projection. That is all I know about it, and I should have said less.

I'm assuming he meant something other than a kind of loop antenna? Loops are H-field beasties.

Sorry, but I actually have forgotten the exact layout of his antenna design, I think it may have actually been a spiral looped planar arrangement, not sure if evenly spaced or more of a logarithmic spiral.

What about coronal mass ejection from the sun, does the plasma not follow the magnetic field lines, and loop back to the sun's surface in places all over the surface?

CMEs and other large plasmas both follow and entrain magnetic fields, dragging the fields along with them as they move, and it is the outskirts of the entrained field that is doing much of the interacting with the ambient one.

Being at the other side of the world I have only just seen all the replies/comments.

What is it that you are trying to make/do? Or, what is the application? If any.

We can wind an inductor which has an external spherical shape but there would be one magnetic axis. That has some difficulties but is possible. And it would probably have an exterrnal field that follows the outer spherical shape pretty closely.

The main question appears to be what type/shape of magnetic field are you able to accept. A spherical field needs to have a return path.

Or do you want "The inductance of a point" source - which is probably an oximoron because if it is a point there can be no current flowing?

Or are you looking to have an inductance which has no external magnetic field outside - or inside - of a nominated spherical shape?

Electrons have no size as far as we know but yet they have angular momentum and a net magnetic moment, so it is possible, yes, even whilst being extremely counterintuitive.

At this point, I'm not trying to do anything. How could I? I simply want to know what the characteristics would be. Is it useful? Well, that depends on answers to questions like, "Can it store and return energy similar to a normal inductor?". I have my doubts.

If I had the mind of Nickola Tesla I might be able to visualize what would happen. Unfortunately, I was not blessed with that ability and I simply did not want to go through an effort if that had already been proven as theoretically worthless.

This question is mostly about the influence of a specific geometry on a man made object. It has nothing to do with the earth or any other cosmic body. I don't know how that got started but it is well outside the scope of this question.

Perhaps then you might consider formulating and posting a script for others to follow when responding to your queries, and just boot the ones that don't conform to the Divine Script. Nice and controlled, like a blinkered donkey. Would that make you happy?

We wouldn't want to cause any discomfort by introducing variants on ideas about which you've already made up your mind.

Later, mate.

<unsubscibe>

At the risk of being a total hypocrite, I would suggest you look at this link, http://www.electronics-tutorials.ws/inductor/inductor.html - the which I have not, - but i am a designer, not an engineer, so i only have to intuit the direction to look for solving problem, not actually solve it, - giving credit where it is due, that is where engineers have an important place. I had a situation where I was a bit out of my depth, designing into a job, (I designed, supplied and supervised the whole job) with a 75kW wind turbine, (induction motor re-done as a generator) on a sea girt island, running a school with all sorts of big air-conditioners and welders, etc, and community night time, so needed power outside of the trade wind time, (app. 10 AM to 11 PM every day) - relatively small battery bank, just under .5MW/hrs, using a 100kW inverter AC DC / DC AC back to back converter, IGBT, etc .you know, and lo and behold it had to have it's output conditioned, - 3 phase supply to the load, - sometimes winging it has it's serious down side, - so, big capacitors, big inductor, bought some very heavy (two of us to carry) traditionally wound, - 200 micro henries? 300? I only know of Henry the 8th I am I am, but, testing it, the bloody thing got very hot, - tried to melt it's way through the cardboard box it was too heavy to lift it out of and we measured over 5000 watts, - not only the inductor obviously failing but far too much drag on a stand-alone system with 24 hour operation. Obviously i am trying to be brief, but a birdie whispered to me "Hollow Cored Inductor" Whacko, a third the price and used (I think) 4 watts, - although at the time I was trying to stop the enthusiastic volunteers from making a 12 metre Pyramid rather than disc as foundation for the tower, - alas failed and they used horrendously more concrete with I suspect little advantage, (perhaps the subject of another post?) so don't remember exactly, - but let it stand so folk can get exercised, it was not bloody much. Sure, 'hollow cored' is not 'spherical', but possibly in the direction you are asking, - contact me directly if you want me to see if I can drag up details. Cheers, Geoff.

Why do you want to know?

"Why do you want to know?"
He said: "But I was curious as to how a magnetic bottle would be created."
Whence the assumption has come that such a bottle would need to be spherical, is another question.

I don't think a magnetic bottle is made from a single inductor, but from a collection of electromagnets, all with their North(1) ends pointed at the 'contained volume' from every direction so their magnetic fields overlap and keep a charged particle 'trapped' inside.

Notes:

1) or South, depending on the charge of the particle you're trying to contain, but they all have to be the same. You're making a 'fake monopole' shell to be the 'lining' of the bottle.

Magnetic mirrors ('bottles') are not built that way. Rather, they are made up of a large region of homogenous (zero-gradient) magnetic field that tapers at the ends. The combination of the charged-particle's helical motion and the field gradient at the ends produces an opposing Lorentz force which drives the particle back into the homogenous zone, hence the name 'magnetic mirror.'

The rings in the central section are a kind of 'Helmholtz coil' whose inter-coil spacing is equal to the coil radius (pic not to scale).

I stand corrected, thank you.

The only 'real' exposure to magnetic bottles I have has is through Sci-Fi, where they are treated as a way to 'store' dangerous particles, not shape particle beams.