任何物理量不应该因为参照系的变化而变化，应满足不变性。因此按照这种理解，电场和磁场不会是独立的物理量（独立的物理量不应因参照系的

磁是电的一种相对论效应,why?
2008-07-30 00:27:30 来自: 千年小茅台(俺是专业炼钢的。)
不太明白.
谁能大概性的解释一下?
. 2008-07-30 00:33:01 Sheenway ((⊙o⊙)…) 同问
> 删除 . 2008-07-30 00:53:16 dy (士不可以不弘毅，任重而道遠。) Feynman说的，去问Feynman...
> 删除 .2008-07-31 18:14:32 [已注销] ...

高人来点拨一下啊...

费曼那文章好长啊...
> 删除 . 2008-07-31 19:40:10 溟蟲 (我將熄滅永不能再回來) http://en.wikipedia.org/wiki/Classical_electromagnetism_and_special_relativity
> 删除 .2008-07-31 19:49:42 [已注销] 电磁波~
> 删除 . 2008-07-31 22:57:38 孤天天 2008-07-31 19:40:10 北溟蟄蟲 (杭州)　　
　http://en.wikipedia.org/wiki/Classical_electromagnetism_and_special_relativity

```那个 我英语差 完全看不懂``
> 删除 . 2008-08-01 00:31:36 溟蟲 (我將熄滅永不能再回來) 　　按照狭义相对论，选用不同的参照系，电场、及磁场的强度是不同。举个简单的例子，我们通常会说运动的电荷产生电流，但是，有电流就意味着有磁场产生。假定原有一堆相对本人静止的电荷，那么我观察到的应只有电场，没有磁场。但是如果我现在以一定速度向某个方向运动，电荷必然相对我运动，意味着有电流存在，也就是有磁场产生了。因为观察者选取参照系的不同，磁场、电场发生了相互转换。磁电互为相对论效应，楼主所言只是其一。
　　
　　任何物理量不应该因为参照系的变化而变化，应满足不变性。因此按照这种理解，电场和磁场不会是独立的物理量（独立的物理量不应因参照系的选取而发生变化），它们不过是一块硬币的两面，本质上是相同的东西。
　　
　　敝人不学无术认为基本应该如此理解。如有谬误，还望见谅。
> 删除 . 2008-08-05 22:11:17 千年小茅台 (俺是专业炼钢的。) 有点明白你的意思了。
谢谢。
> 删除 . 2008-08-06 19:10:17 Everett 北溟蟄蟲所言极是。

所谓电磁场的狭义相对论效应，就是指在一个惯性系中看到的“纯”电场，对于另一个相对运动的惯性系来说是既有电场又有磁场的混合场；类似地，在一个惯性系中看到的“纯”磁场，对于另一个相对运动的惯性系来说是既有磁场又有电场的混合场。在不同的惯性系测量到的电场E和磁场B可以是完全不同的，但是它们之间有一个狭义相对论变换，可以将一个惯性系中的电磁场变换到另一个惯性系中去。在这个变换中，（对于真空中的电磁场）E^2 - c^2 B^2 和 E.B 是两个不变量，就好象真空光速是时空坐标变换的不变量一样。

比起时空的相对论效应，电磁场的相对论效应更容易被人们观测。比如一根导体棒做切割磁感线运动，产生“动生”电动势，导体两端积累异号电荷，就是一个相对论效应。对于挥动导体棒的实验者来说，空间中只有一个匀强磁场，没有电场，异号电荷积累乃是洛仑兹力作用于电荷的结果。如果我们变换到导体的参考系中去，那么我们怎么解释导体两端的电荷积累呢。按照狭义相对论，原来的匀强磁场将变换为另一个匀强磁场和一个垂直方向上的匀强电场的混合场。于是我们可以解释，由于电场的出现，在导体上产生静电感应，导致了异号电荷的分离。因此，我们所熟知的“动生电动势”就是磁场的相对论效应。

我们可以类比地推想：既然有“动生电动势”，是否也有“动生磁动势”呢？也就是切割电场线，会不会有感应磁场呢？答案是肯定的。例子如北溟蟄蟲所说。由此，我们总结：电磁场的动生感应，就是电磁场的狭义相对论效应。动生电场是磁场的相对论效应，同样，动生磁场也是电场的相对论效应。

在运动参考系中，磁场会“部分地”转化为电场，而电场也会“部分地”转化为磁场。由此，我们再次看到了电场和磁场的密切关系。我们将一个原本统一的电磁场人为地划分为电场部分和磁场部分，其实是不妥的。电磁场的相对论性就是说，不存在绝对的电场和绝对的磁场，任何关于电磁场的划分都是相对于参考系而言的。正如北溟蟄蟲所说的：
---------------
电场和磁场不会是独立的物理量（独立的物理量不应因参照系的选取而发生变化），它们不过是一块硬币的两面，本质上是相同的东西。
---------------
而所谓的本质就是电场和磁场的统一，也就是电磁张量F。电磁张量F就是一个狭义相对论协变的物理量。
> 删除 . 2008-08-06 21:43:52 溟蟲 (我將熄滅永不能再回來) 俺是门外汉，非物理出身，连蒙带猜......

还是要靠学物理的牛人来解释，才是正解：）
> 删除 . 2008-08-06 22:51:32 newone (认真是美德) 电磁一体
相对论的四维空间下，电和磁一起成为一个四维张量
好像是这么说的吧^_^电动刚学完不久
> 删除 . 2008-08-14 14:46:48 entropy (I LOVE G O G L E) 好东西，好东西，鼓爪爪
> 删除 . 2008-08-14 14:55:17 thin可ing 人类太复杂，还是回到二十四维空间生存比较好
——蜷缩也是一种生存态度
> 删除 . 2008-08-19 22:08:34 和平超人 学了电动力学就全明白啦
> 删除 . 2008-08-19 22:55:43 远雷 (是受！是受还不行吗！！！) 似乎……还是没看懂
> 删除 . 2008-08-22 20:45:36 栋栋 请参考麦克斯韦方程式

没有磁荷，有电荷


A Potential Last Gasp of Volatility Next Week and an AUDJPY Trade to Pair it With?
By John Kicklighter, Currency Strategist
11 December 2010 02:27 GMT
There are two sides to the trading coin going into next week. On one side, we know that December (particularly the second half) is historically a quiet time for the speculative markets due to holidays and tax season for a generous segment of the global community. On the other hand, we are carrying over a lot of significant, fundamental risk that has yet to be resolved. At the top of my list of concerns are European financial troubles exacerbated by an Ireland bailout vote, Chinese efforts to curb capital inflow after the strong CPI reading with potential further rate hikes and US efforts to flood the market with stimulus to unstabilize the natural balance in the market. What can we expect from these events? There is certainly the potential for volatility; but that doesn't necessarily mean that we will get follow through. With the broader financial markets looking at a natural lethargy in liquidity, it will be difficult to sustain true trends. I will err on the side of caution with expectaitons of restrained markets. That means, lower position size, offset theme exposure (long risk in one place, short risk in another) and reasonable targets and stops.

....

Looking out over the next week, there is significant pontential seen in a number of pairs. For those that I am not currently tracking, it is more about volatility and breakout potential. EURJPY is the most highly charged with congsestion below 111.50/75. A breakout here is the most likely with the mix of European issues as well as the general threat of a sentiment stir. Perhaps the most appealing breakout candidate though is AUDJPY above 82.80 as we don't necessarily need a risk aversion move to get this pair moving higher. NZDJPY can see a bearish channel break below 62; but it would probably be a better candidate should sentiment hold up and that range pattern hold as well. I will be more dubious of the longer-term potential in GBPUSD and AUDNZD. The former is almost purely fundamental until appealing technicals setup but AUDNZD has a great fundamental charge for advance and the technical appeal of a triple top around 1.32.

.....

For those currently on the book, there was moderate movement on most fronts. The most notable development was EURNZD's tag of its second target at 1.7635. Reasonable targets worked well for this pair. The short EURUSD from 1.33 and long NZDUSD from 0.7450 balance each other out should there be a significant drive in the dollar and/or risk trends come next week. USDCAD is still looking for the second half to hit its target at 1.0185 but a trailed stop pared its risk. And, USDJPY is a long-term setup that has very unique fundamentals. Perhaps the most unilateral risk in the mix is the short AUDCAD short from 0.99. A stop of 150 points is wide for this pair; but the reward potential in a long-term reversal is substantial enough to offset it. That being said, such an outcome requires a trend...

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