Magnetic Fields · 磁场
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| magnetic field/mæɡˈnetɪk fiːld/ | 磁场 | cí chǎng |
| pole/pəʊl/ | 磁极 | cí jí |
| tesla/ˈteslə/ | 特斯拉 | tè sī lā |
| monopoles/ˈmɒnəʊpəʊlz/ | 磁单极 | cí dān jí |
Why does a compass needle always swing to the north?
- Let a compass settle and it lines up along an invisible direction.
- A magnetic field 磁场 fills the space around every magnet.
- The needle is a tiny magnet turning to follow that field.
- This unit builds the whole story of magnetism from this field.
为什么指南针的指针总是摆向北方?
- 让指南针停稳,它就沿一个看不见的方向排齐。
- 一个磁场充满每个磁体周围的空间。
- 指针是一个跟随那个场转动的微小磁体。
- 这个单元从这个场建立起磁学的整个故事。
Poles and field lines
- Every magnet has a north and a south pole 磁极.
- Field lines run from N to S outside the magnet (and S to N inside).
- The field $\vec B$ is a vector; its unit is the tesla 特斯拉 (T).
- Where the lines crowd, the field is strongest.
磁极与磁感线
- 每个磁体都有一个北极和一个南极。
- 磁感线在磁体外部从 N 走到 S(内部从 S 到 N)。
- 场 $\vec B$ 是矢量;它的单位是特斯拉(T)。
- 磁感线密集处,场最强。
See a magnet's field · 观察磁铁的磁场
Explore the field lines looping from north to south around a bar magnet. · 探索条形磁铁周围从北极到南极环绕的磁感线。
Outside a bar magnet, the field lines run: · 在条形磁铁外部，磁感线走向：
Outside, field lines run from the north pole to the south pole. · 外部磁感线从北极指向南极。
The SI unit of magnetic field strength is the . · 磁感应强度的SI单位是。
Magnetic field $B$ is measured in tesla (T). · 磁感应强度$B$以特斯拉（T）为单位测量。
Like poles repel
- Bring two like poles together and they push apart.
- Opposite poles pull together — just like charges.
- The force acts through the field each magnet makes.
- A compass needle turns until its N points along the field.
同极相斥
- 把两个同极靠近,它们互相推开。
- 异极互相拉近——就像电荷一样。
- 力通过每个磁体产生的场作用。
- 指南针的指针转到它的 N 沿着场为止。
Two north poles brought close together will: · 两个北极靠近时会：
Like poles repel, just like like charges. · 同名磁极相互排斥，如同同种电荷。
No magnetic monopoles
- You can never isolate a single N or S pole.
- Cut a magnet in half and each piece grows a new pair of poles.
- There are no magnetic monopoles 磁单极 — poles always come in pairs.
- This is why magnetic field lines always form closed loops.
没有磁单极
- 你永远无法孤立出单个的 N 极或 S 极。
- 把磁体切成两半,每一块都长出一对新的极。
- 没有磁单极——磁极总是成对出现。
- 这就是为什么磁感线总是形成闭合回路。
Cut a bar magnet in half. You get: · 将条形磁铁切成两半。你会得到：
No monopoles: each half grows its own N and S. · 不存在磁单极子：每一半都会长出属于自己的N极和S极。
Magnetic field lines always form closed loops because there are no magnetic monopoles. · 磁感线总是形成闭合回路，因为不存在磁单极子。
With no monopoles, lines have nowhere to start or stop — they close. · 由于没有磁单极子，磁感线无处起始或终止 —— 它们闭合。
Select all · 所有 true statements about magnetic fields. · 选择关于磁场的所有正确陈述。
N-to-S outside, no monopoles, closed loops. A single pole can never be isolated. · 外部N到S，无磁单极子，闭合回路。单极永远无法被孤立。
The Earth is a giant magnet
- The Earth makes its own magnetic field, roughly like a bar magnet.
- A compass needle aligns with it, pointing toward magnetic north.
- The field also shields us from some of the Sun's charged particles.
- Sailors used this long before anyone understood why it worked.
地球是一个巨大的磁体
- 地球产生自己的磁场,大致像一个条形磁体。
- 指南针的指针与它对齐,指向磁北。
- 这个场还屏蔽我们免受一些来自太阳的带电粒子。
- 水手们早在有人明白它为何有效之前就用它了。
You cut a bar magnet exactly in half at its middle.
- You do not get a separate N piece and S piece.
- Each half becomes a smaller magnet with its own N and S.
你把一个条形磁体正好从中间切成两半。
- 你不会得到一块单独的 N 和一块单独的 S。
- 每一半都变成一个更小的磁体,有它自己的 N 和 S。
Magnetic field lines always form closed loops — they never start or stop on a pole the way electric lines start on charge. That is because there are no magnetic monopoles; N and S always come together.
磁感线总是形成闭合回路——它们从不像电场线起于电荷那样起于或止于某个磁极。这是因为没有磁单极;N 和 S 总是在一起。
A magnetic field $\vec B$ (in tesla) surrounds every magnet, with lines running N to S outside. Like poles repel, opposite attract. There are no magnetic monopoles, so field lines always form closed loops. The Earth itself acts as a giant magnet.
一个磁场 $\vec B$(单位特斯拉)环绕每个磁体,磁感线在外部从 N 到 S。同极相斥,异极相吸。没有磁单极,所以磁感线总是形成闭合回路。地球本身就像一个巨大的磁体。