$\left\{ \begin{array}{c} \nabla \cdot \mathbf{E} = \frac {\rho} {\varepsilon_0} \\ \nabla \cdot \mathbf{B} = 0 \\ \nabla \times \mathbf{E} = - \frac{\partial \mathbf{B}} {\partial t} \\ \nabla \times \mathbf{B} = \mu_0\mathbf{J} + \mu_0 \varepsilon_0 \frac{\partial \mathbf{E}} {\partial t} \end{array} \right.$
$\left\{ \begin{array}{c} \nabla \cdot \mathbf{D} = \rho_f \\ \nabla \cdot \mathbf{B} = 0 \\ \nabla \times \mathbf{E} = - \frac{\partial \mathbf{B}} {\partial t} \\ \nabla \times \mathbf{H} = \mathbf{J}_f + \frac{\partial \mathbf{D}} {\partial t} \end{array} \right.$
I have no shirt tonight
今晚我褪去衣衫
Because I want to show you
因为我想为你展示
A set of 4 beautiful equations
一组四个美丽的方程
They describe the world's most beautiful side.
它们描绘了世界最美的一面
Current, Waves and Light
电流、波和光
Come here, look at them
过来,看看它们
They are here on my chest
它们就在我的胸前
so close to my heart
如此贴近我的心脏
just like you, I'm going to tell you tonight
就像你一样,今夜我将为你讲述
About the waves and light.
波与光的奥秘
Your exam is tomorrow
你的考试就在明天
don't worry, we'll study until dawn
不要担心,我们会学习到天亮
close like nucleons
像核子一般依偎
We start with the charge
我们从电荷开始
electrons and protons, equals and opposite:
电子和质子 (带的电荷)大小相等而(电性)相反:
it's 1.6 at 10e-19 coulomb.
大小是1.6×10-19库仑
Electromagnetic force is so intense
电磁力是如此强烈
sometimes it repulses, sometimes it attracts
它有时排斥,有时吸引
sometimes like you and me, we turn around
有时就像你和我,我们转身
Study the material for it to be found
研究物质来寻找它
Our Law is K, Q1 Q2 on r squared
The shorter the distance, the greater the attraction
距离越短,引力越大
The spankings I'll lay on your skin tonight
今晚你身上要挨我的打
while you repeat the Columbian force
当你重复承受库仑力时
These equations describe how electricity and magnetism work
这些方程描述了电和磁如何作用
Our feeling, interaction,
我们的感觉、互动
Our sight and sensation
我们的视觉、知觉
I can feel your charge, it's positive
My electron cloud is so attracted
我的电子云已被深深吸引
Say my name, call me Sensei.
叫我的名字,叫我老师
Let's begin our Hide'n'Seek game:
让我们开始捉迷藏游戏:
like charges in insulators' gap,
就像绝缘体间隙中的电荷一样
try to reach me, come to the other side.
试着靠近我,到另一边来
You're finally here, close to my chest again,
你终于来了,再次靠近我的胸膛
Ready to start, tell'em slowly
准备开始,慢慢告诉他们
You surround me with your surface
你用你的曲面包覆着我
I'm your electric flux
我是你的电通量
Maxwell's second equation says:
麦克斯韦第二方程说:
the magnetic field is made by lines
磁场由场线构成
Closed lines from a pole to another
从一个磁极到另一个磁极的闭合场线
no sources, they'll always return
没有场源,它们总是会返回
'cause in the end, B flux is always zero
Hold me now, we can't be detached
现在抓紧我,我们不能分离
3rd equation, it may change in form
第三个方程,它可能会改变形式
If we have no magnetic field
如果我们没有磁场
So we can define it through a potential
所以我们可以用势来定义它
this field is conservative
这个场是保守场
The result is zero again
结果又是0
Let's make it harder
让我们增加些难度
You can make B vary
你可以让B变化
The situation isn't static anymore!
情况不再是静态的!
Here it comes: Faraday induction
它来了:法拉第效应
The last one it's also called the Ampere's law
最后一个也叫(麦克斯韦-)安培定律,
With static fields it's easy
在静场下,它会很简单
is just permeability
就是磁导率
times concatenated currents, Locally is just J,
But if we vary
但是如果我们(让电场)变化
We need to add one more thing
我们需要(在方程中)再加一项
Maxwell found a way to include
麦克斯韦找到了一种方法去包含
time-varying electric fields
时变电场(的影响)
Adding the displacement current
增加位移电流(的一项)
locally it's just the variation in time of E.
在局域就是E随时间的变化
Here we have our special laws, All unified
于是我们得到了这特殊的定律,包纳一切
a symmetric coherent set
这对称统一的一组
Maxwell's Equations
麦克斯韦方程组
Protons, electrons and light
质子、电子和光
They seem to be different
它们看起来似乎不同
but they are the same
但又是一样的
did you know these electromagnetic waves
你知道吗?电磁波
have the same speed of light
有和光相同的速度
and hence are the same
因此它们就是同一种东西