Talk:Weber (unit)

From Wikipedia, the free encyclopedia

WikiProject Physics This article is within the scope of WikiProject Physics, which collaborates on articles related to physics.
Start This article has been rated as start-Class on the assessment scale.
??? This article has not yet received an importance rating within physics.

Help with this template This article has been rated but has no comments. If appropriate, please review the article and leave comments here to identify the strengths and weaknesses of the article and what work it will need.

The page says, "if the current flowing through a loop changes, it will induce a magnetic field." I think this is incorrect. Don't static currents induce magnetic fields? --Smack (talk) 05:41, 28 Mar 2005 (UTC)

It's not very clear in the article but "a changing current induces a magnetic field" does not exclude "a static current induces a magnetic field" too. In fact, from \nabla\times\mathbf{H}=\mathbf{J}+\frac{\partial\mathbf{D}}{\partial t}we see that any current \mathbf{J}, static or otherwise, not negated by the effects of the (usually negligible) displacement current \partial\mathbf{D} / \partial t, will give rise to a non-zero curl of \mathbf{H}, implying that \mathbf{H}=\mathbf{B}/\mu is non-zero. Md25 08:17, 13 Apr 2005 (UTC)
I think that it's much more than "not very clear". If it had read, 'a magnetic field', then you would have been correct. However, what is the significance of the stipulation of a changing magnetic field, if not the exclusion of a static magnetic field?
P.S. My physics text used 'B' and 'E' for electic and magnetic fields. Do 'H' and 'D' belong to some non-SI system of units? --Smack (talk) 04:50, 15 Apr 2005 (UTC)
B is sometimes called magnetic field, but is more appropriately called magnetic flux density, whereas H is in fact the magnetic field. E is the electric field, while D is the confusingly-named electric displacement field. --Laura Scudder | Talk 01:50, 28 Apr 2005 (UTC)
Magnetic flux density redirects to magnetic field density, which says that they're the one and the same. --Smack (talk) 01:52, 30 Apr 2005 (UTC)
Yeah, I said it's confusing and inconsistent. Most intro classes never need to use H because they don't work in materials, and so call B the magnetic field, but as soon as you're within a material, a physicist would call H the magnetic field (historically because that's what instruments measure). --Laura Scudder | Talk 20:44, 4 May 2005 (UTC)