Energy Stored In Air Gap

  have a question.

is this Radio Shack? do you have answers?  ;D


i was reading up on reluctance and noticed that energy is somehow stored in the air gap of a transformer,

can anybody explain how?

how can air store anything besides molecules?  ???

michael phelps, what happened?  i smoke a bowl for you, my frend, 8)

It's not often we can help you out CJ

This article explains it, scroll down to gap energy.

http://info.ee.surrey.ac.uk/Workshop/advice/coils/gap/index.html

Seems like all the field energy ends up in the gap.

there you go

best
DaveP

My academic background would have me believe its stored in the magnetic field.  However all the math in the world doesn't help me to actually visualize EM fields. I long for a camera that could photograph EM fields in circuits the same way thermal imaging photographs heat. I'd love to see an IC radiating a field or a trace carying a fast edge rate induce current in a neighboring trace and know for sure which one and to what degree. But then what would I do at work all day?

Hmm, so is the air ionized?

Riggler,

Electromagnetic radiation stretches from audio through radio, microwave, infra red, light and UV.  It is only when it becomes sufficiently energetic enough to dislodge electrons that it is said to be ionising, like gamma radiation.  So the answer is no, it is not ionised.  The magnetic field is propagated in the air like radio waves, only lower frequency.

best
DaveP

The energy isn't stored in the air gap in the way energy is stored in the dielectric of a capacitor, available to be released later.

It's more like the way the voltage across a resistor in a constant current circuit increases when you increase the value of the resistor. You could say there's more energy across the resistance but it isn't "stored" there.

Adding the gap to the magnetis circuit is like adding resistance to an electrical circuit. The field potential shows up there but it isn't being stored. It actually reduces the storage capacity by adding leakage.

CJ said:

how can air store anything besides molecules?  ???

Click to expand...

The air doesn't store anything. It's the magnetic field that stores the energy. The magnetic field can exist more effectively in a vacuum than in a conductor (metal transformer core), where it would induce currents in turn resulting in an opposing magnetic field (and cancel itself out). It's all down to Maxwell's equations. Similarly, in a capacitor, the electric field exists more effectively in a dielectric (insulator) in the gap between the plates, rather than in the plates themselves. It just so happens that electric field lines start and finish at charged particles (and have no loops) which makes it easy to imagine charges moving, whereas magnetic fields have no associated particles and only consist of loops (Gauss's law).

CJ said:

how can air store anything besides molecules?  ???

Click to expand...

Energy has to go somewhere. No matter how little. Heat ?

Adding a gap decreases the energy storage capacity of a magnetic core inductor.

> energy is somehow stored in the air gap

Not the AIR-gap. The gap. Doesn't have to be air, or paper.

Think of the ether. Not the engine-juice you snort when bored, the ether which permeates the universe to carry waves of light (electromagnetic waves).(*)

Light waves (any electromagnetic wave) stretches/compresses the ether, like ripples on a pond.

Think of a Leyden Jar(**). Or that 0.047uFd AreoVox capacitor under your bench. Electrical energy is stored "in the jar", electrical tension. The ether is stretched.

This tension exists both in the iron core and in the gap. However the iron conducts 1000 times better than nothing (air or paper is practically nothing), so 99.9% of the tension energy is in the gap. Oh, a bit less because core-path is much longer than gap-path, but even quite small gaps will hold most of the magnetic tension. (if they are too small to do that, then there is no point in having a gap.)

(*)Yes, the ether theory was "disproved" in a famous experiment, a failure which led to Eistein's more complicated theories about how light and stuff really works. But they had to squint real hard to find a way to doubt the ether theory. For everyday folks like us, either theory is valid-enough for rock&roll.  And ether-like theories have recently been proposed to cover stuff like missing mass ("dark matter") which don't balance-out with observations and Relativity or Quantum theories.

(**) BTW, Leyden is where Einstein gave his address which replaced ether with relativity.

Actualy, Einstein's 1920 address at Leyden _says_ there is ether, but you can't track it so you can't measure its motion:

Recapitulating, we may say that according to the general theory of relativity space is endowed with physical qualities; in this sense, therefore, there exists an ether. According to the general theory of relativity space without ether is unthinkable; for in such space there not only wonld be no propagation of light, but also no possibility of existence for standards of space and time (measuring-rods and clocks), nor therefore any space-time intervals in the physical sense. But this ether may not be thought of as endowed with the quality characteristic of ponderable inedia, as consisting of parts which may be tracked through time. The idea of motion may not be applied to it.

For the lump of iron on your bench, "motion" is not a factor, so the M-M failure does not matter.

It must be remembered that in that time there was a lot of silly talk of things like "fixed points in the ether" from which to observe events.

Nowadays I think concepts like "quantum vacuum fluctuations" allow there to be what we simple folk could consider to be a medium of propagation.

CJ said:

i was reading up on reluctance and noticed that energy is somehow stored in the air gap of a transformer

Click to expand...

No energy is stored in the gap; energy exists in the gap as long as the excitation exists, i.e. as long as there's current in the coils or as long as a permanent magnet is affixed to the core.
Only permanent magnets store magnetic energy.
The analogy with capacitors is limited because everything with two armatures is a capacitor, but not everything is a permanent magnet.
In a capacitor, the energy is not specifically stored in the air, because a capacitor with vacuum between its armatures stores energy. This energy is stored by a modification of the inter-armature space, which is the electric field.
Just the same, energy exists in the space between poles; this space may be constituted of air, vacuum, gas, plastic, wood, non-ferrous or ferrrous metals, ferrofluid. The magnetic energy will be distributed in accordance wirh magnetic permeability of the various elements of this "gap". Depending on the ferrous or non-ferrous nature of the elements, magnetic energy may be stored. But not in air.
And there's no need to invoke the spirit of ether for that. Ether may or may not exist, it is not necessary for this discussion.
When I see that people several rugs higher than me on the cognitive scale cannot agree on the existence of it, I hesitate at evocating it.