Talk:Induction loop
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I have cleaned up this article as much as I could. From 1979 until 1993 I was in the USAF and was a telecommunications technician, so I knew what he was talking about. The person who wrote this article was obviously an engineer of some kind becuase he was talking about some really deep subjects. Perhaps the person who wrote this piece could go back through and look at it again.
--TracyRenee 12:32, 30 Mar 2005 (UTC)
- I've looked at the cleaned-up version as well as the first version and I'm still baffled. Most of the discussion sounds like it should be under electromagnetism and it doesn't get around to defining its subject. I'd VfD or redirect this to electromagnetism, I don't think it's salvageable. --Wtshymanski 21:07, 16 Apr 2005 (UTC)
[edit] Temporary Home for material NOT about induction loops
Just cant think what this stuff is doing here. Can someone write something about induction loops?Light current 02:30, 15 August 2005 (UTC)
- Trying to integrate this material into electromagnetism or inductance could be verry tricky and time consuming unless you really know the difference between 'conservative' and 'non conservative' etc.. Anyway is there anything here that is not already covered on other pages? I think not. VfD Light current 02:40, 15 August 2005 (UTC)
[edit] Description
There are two kinds of fields: conservative and non-conservative. For a conservative field, the integration around a loop is zero. In a conservative field the work done by the force that generates the field depends on end points only and is independent of the path. Fields associated with the electric static force and the gravitational force are examples of conservative fields. For a non-conservative field, an electrical field is induced by a changing magnetic field. The force in a piston of a thermal engine is also non-conservative.
Since the electrical field induced by a changing magnetic field is non-conservative, the work done by this electrical field depends on the path. The inductance is associated with this path dependent work. It is for this reason that inductance is very sensitive to paths. To translate this into electrical engineering concepts, an inductance is very sensitive to the shape of the devices because the shape will effect the path of the current flow and thus the non-conservative work involved.
Since the work done by a non-conservative field depends on the path, it is not practical to talk about potential. If one tries to define a potential for given end points, there would be an infinite number of potentials involved. It is for this reason that we talk about the non-conservative work associated with a given loop. Here is how inductance comes into play.
Mathematically, inductance, indicated by the symbol "L", can be defined in two different ways:
- The total magnetic flux in a closed loop divided by the current that generates the flux
- The total work done by the vector potential when going around a loop divided by the current that generates that vector potential
If the current belongs to the same loop, we call the inductance self inductance. If the current belongs to another loop, we call it mutual inductance, using symbol "M".
While inductance is defined in terms of loops, not all examples must actually form a loop, i.e. a solenoid. A geometry that does not form a loop, one can always determine a loop that will have the same inductance effect. For example, in the case of a straight line, one may add two lines at both ends that are perpendicular to the current and let both lines be infinitely long. At infinity, one adds another line of any shape to close the loop. The justification for this is that a line perpendicular to the current will not have inductance associated with the current because it is penpendicular to the vector potential given by the current. As for the line at the far end, there is no inductance since the vector potential is zero at infinity.
The same principle can be applied to general shapes. Mathematically, it is a matter of numerical computation. In principle, for any 3D geometrical configuration, inductance can be calculated.
Based on the definition of inductance, the larger the loop, the larger the inductance. In the example above, the straight line is equivalent to an infinitely large loop. In general, a non-closed geometry has larger inductance than a closed loop.
This fact is quite important in high frequency electronic designs. At very high frequencies inductance contributes to total impedance. Thus it has an impact on crosstalk and reflection and strongly affects signal quality and signal delay. Therefore, correct loop concepts can help in improving the design of better circuits. For example, high frequency design demands small current loops.
Inductance also plays an interesting role in quantum mechanics, particularly the Aharonov-Bohm effect. This effect states that when a pair of charges pass around a long solenoid, the relative phase of the two charges will change. The change can be verified by the interference patterns on a screen. The implication is that a nonlocal quantum effect takes place. Although there is no magnetic field outside the solenoid, the particles are somehow affected by the field. Nonlocal effects plays an important role in current quantum information science.
[edit] introduction for laypeople?
I still have no idea what one of these does aside from that it's used in metal detectors and traffic systems. Can someone smarter than me write an intro? Lot49a (talk) 19:07, 17 April 2008 (UTC)
