Talk:Wave impedance
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Some changes made:
The largest change is I added the full formula for wave impedance in a material that has conductivity, and mentioned that in this case the wave impedance is complex, rather than a simple real number.
I don't think 1/36pi is the correct value for the permittivity of free space. It is normally given as 8.854 x 10^-12.
The link to electric permittivity now points to the permittivity page (it used to be an empty page).
The "medium" link at the end used to point to a page explaining that medium means in between large and small. This is obviously not the right kind of medium, so it now points to medium (bearer), which is not highly relevant but is closer to the intended meaning.
Also noted that eta is used by many engineers for wave impedance to avoid confusion with electrical impedance.
[edit] Face lift
Most this atricle has been pulled from the cited source (Copy and Paste.) I think I'm going to rewrite it so it's more like a Wiki article and not a government documnet. -eaglescout1984 21 Nov 2006 4:20 GMT
[edit] Bad stuff
There's some bad stuff on this page (sorry to be so critical!). I'm just going to delete the worst bit...
- Designing a wave guide
- In electrical engineering, the wave impedance is an important factor to consider when designing a waveguide. The parameters of the medium must match up such that the wave impedance will be the desired value. For example, coaxial cable used for TV signals has a designated wave impedance of 75 Ω. The desired wave impedance gives the wave of a particular range of frequecies a better propogation.
...that's better. The main problem with this section is that it confuses the characteristic impedance of a line (which is V/I) with the wave impedance in the cross-section of the line (which is E/H). Also it doesn't make much sense.
No, 1/36π isn't the correct value for the permittivity of free space. --catslash 01:07, 29 December 2006 (UTC)
Some other stuff that needs addressing:
- a ratio is dimensionless (OK - minor point)
- we ought to say the transverse components of the electric and magnetic field (because it might not be a TEM wave)
- the implication that the wave impedance is not an electrical impedance is surprising!
- it's not clear how the wave impedance differs from the electromagnetic impedance - does it? (I've never heard of electromagnetic impedance).
- presumably, dividing Z0 into the refractive index should be dividing Z0 by the refractive index --catslash 01:45, 29 December 2006 (UTC)
-
- Either ratio is wrong and a ratio can have a dimension if the numerator and denominator have different dimensions, or this and a load of other pages need fixing, e.g. impedance,electrical impedance,mass-to-charge ratio. It may be correct to say that ratios never have dimensions in pure maths, but I think it's common enough in physics/engineering to use the term this way that it is indeed a minor issue.
- Transverse - agree
- I can't find the phrase not an electrical impendance. It is obviously related to electricity, however it is not the same as Electrical impedance to my knowlegde - since that applies to a finite object (e.g. a resistor or a capacitor) and wave impedance applies to a substance in general (e.g. air, water). This could arguably be worded better. I think the point that is supposed to be made is that you may find eta as well as Z used to symbolise wave impedance.
- According to wikipedia, electromagnetic impedance is the same thing with the formula written wrong. These two pages should probably be merged, if indeed electromagnetic impedance exists. Google returns 704 results and the first page looks like a lot of duplicates and that same wikipedia entry. No idea.
- Sounds right, I'm feeling too lazy to check it though.
- 217.44.114.250 03:28, 14 January 2007 (UTC)
[edit] Confusion
This article confuses:
- wave impedance
- characteristic impedance
- (characteristic) intrinsic impedance of a medium
I feel moved to start sorting this out. --catslash 13:45, 7 May 2007 (UTC)
