Talk:Space charge

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Comments

We need to disambiguate EMF, but I'm not into EE encough to know in this case whether it should point to electromagnetic field or Electromotive force. Someone please help. -Anthropos 13:06, 20 Dec 2003 (UTC)

It appears from the context that it should point to electromotive force, so I've changed it from the automated disambiguation.

Also, I've wikified Krishnavedala's contributions a bit. I've unlinked Image:Childlaw.JPG, which seems to me that it should be removed; I have no idea how to go about this. I think I've translated it to TeX properly, but the image was rather ambiguous. I can't say anything on the accuracy or relevance of what Krishnavedala has added; I'm only a sophomore physics major looking for stuff to clean up. If anyone can improve this section, please do so. 24.118.220.84 02:10, 9 Jun 2005 (UTC)

--
Krishnavedala image Childlaw.JPG
ChildLangmuirLawGraph1.svg
"I can't say anything on the accuracy or relevance of what Krishnavedala has added"
As far as I can tell, the Child's Law image ChildLangmuirLawGraph1.svg is just wrong. It appears to plot V^3, not V^(3/2) or V^1.5.
Unless somebody objects, I will post a graph of V^1.5.
PRR (talk) 23:10, 19 June 2011 (UTC)[reply]

minor edit

I added definitions of the variables in the equation for Child's law.

  --Geoff

I wonder what the definition for ν is —Preceding unsigned comment added by 71.238.185.224 (talk) 19:25, 12 April 2009 (UTC)[reply]

I cannot find any definition for ν. It is not in Child's original article (Phys. Rev. 32, 492 (1911)). Another paper I (randomly) found (Ang et al, Phys. Plasmas 13 056701 (2006) ) writes Child's Law as:

J={\frac {4\epsilon _{0}}{9}}{\sqrt {2e/m_{e}}}{\frac {V^{3/2}}{D^{2}}}

. Numerically, one finds

{\frac {4\epsilon _{0}}{9}}{\sqrt {2e/m_{e}}}=2.33\times 10^{-6}

, as written in the current article. So I think the

\nu

should be removed, and the numerical prefactor replaced by the relevant physical quantities. Chucklapuck (talk) 19:44, 15 October 2009 (UTC)[reply]

Mott's (?) steady-state space-charge-limited conduction

It is clear that the relation given in the section 'Mott's limited steady-state..' has anything to do with Mott? Can anyone give a reference for this? This expression already appeared in early papers by Shockley (see e.g. W. Shockley and R. C. Prim, Phys. Rev. 90, 753 - 758 (1953), Eq.(1.13)). Chucklapuck (talk) 19:44, 15 October 2009 (UTC)[reply]

It is also known as Mott-Gurney-Law $j\propto U^{2}$ (Space-charge Limited Current, SCLC). Hear the Cilds-Law $j\propto U^{1.5}$ is refered to as SCLC? But isn't SCLC $j\propto U^{2}$ ? Makes no sense... —Preceding unsigned comment added by 77.176.79.30 (talk) 16:14, 22 August 2010 (UTC)[reply]

what about non-high-vacuum?

"If the "vacuum" has a pressure of 10-6 mmHg or less, the main vehicle of conduction is electrons." this exposes only high vacuum conditions. what if I have a plasma within a gas at a pressure of, say, 15 to 40 torr? —Preceding unsigned comment added by 99.233.186.4 (talk) 06:20, 24 November 2010 (UTC)[reply]

Incorrect graph

Thank you for pointing out the error. The graph of Child's Law is now rectified. --ElectroKid 17:23, 22 June 2011 (UTC) — Preceding unsigned comment added by Krishnavedala (talk • contribs)

Error in further Generalization

It seems like the calculation by conley in his 1995 paper has an error in it, it implies that increasing starting velocity decreases total current. Seems like the negative sign should be a positive sign, that aligns with the formula from this paper https://www.sciencedirect.com/science/article/abs/pii/0168900294912831 Further discussion in this thread https://physics.stackexchange.com/questions/112548/child-langmuir-space-charge-law-for-non-zero-cathode-potential-non-zero-initial 216.171.24.221 (talk) 07:52, 12 November 2024 (UTC)[reply]