Electric Charge and Electric Force · 电荷与静电力
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| charge/tʃɑːdʒ/ | 电荷 | diàn hè |
| Coulomb's law/ˈkuːlɒmz lɔː/ | 库仑定律 | kù lún dìng lǜ |
| coulomb/ˈkuːlɒm/ | 库仑 | kù lún |
Rub a balloon on your hair — now it sticks to the wall
- Rub a balloon on your hair and it clings to a wall, defying gravity.
- Rubbing moved invisible charge 电荷 from one surface to the other.
- Charges come in two kinds, and they push and pull without ever touching.
- The rule for that push and pull is Coulomb's law 库仑定律.
把气球在头发上蹭一蹭——它就贴在墙上了
- 把气球在头发上蹭一蹭,它就贴在墙上,抵抗着重力。
- 蹭动把看不见的电荷从一个表面移到了另一个表面。
- 电荷有两种,它们不接触也能互相推拉。
- 这种推拉的规则是库仑定律。
Two kinds of charge
- There are positive and negative charges (protons are +, electrons are −).
- Like charges repel; opposite charges attract — the fundamental rule.
- Charge is measured in coulombs 库仑 ($\text{C}$); the electron's charge is tiny.
- An object is charged when it has unequal numbers of protons and electrons.
两种电荷
- 有正电荷和负电荷(质子是 +,电子是 −)。
- 同种电荷相斥;异种电荷相吸——最基本的规则。
- 电荷以库仑($\text{C}$)量度;电子的电荷很微小。
- 当物体的质子数和电子数不相等时,它就带电。
Two negative charges are placed near each other. They will: · 两个负电荷靠近放置。它们将会：
Like charges repel — two negatives push apart. · 同种电荷相斥——两个负电荷互相推开。
Electric charge is measured in . · 电荷的单位是。
Charge is measured in coulombs ($\text{C}$). · 电荷以库仑（$\text{C}$）为单位测量。
A positive and a negative charge will: · 一个正电荷和一个负电荷将会：
Opposite charges attract. · 异种电荷相互吸引。
Coulomb's law
- The force between two point charges is $F = \dfrac{k q_1 q_2}{r^2}$.
- It grows with each charge and falls off as the inverse square of the distance.
- Double the distance and the force drops to a quarter — just like gravity.
- $k$ is Coulomb's constant; the direction is along the line joining the charges.
库仑定律
- 两个点电荷之间的力是 $F = \dfrac{k q_1 q_2}{r^2}$。
- 它随每个电荷增大,并按距离的平方反比衰减。
- 距离加倍,力降到四分之一——就像引力一样。
- $k$ 是库仑常数;方向沿连接两电荷的直线。
The field of a charge · 电荷的电场
Change the charge and see the electric field it creates around itself. · 改变电荷并观察其周围产生的电场。
Two charges are brought from $2\ \text{m}$ apart to $1\ \text{m}$ apart. By what factor does the force increase? · 两个电荷从 $2\ \text{m}$ 分开变为 $1\ \text{m}$ 分开。力增加了多少倍？
Halving $r$ multiplies $1/r^2$ by $4$ — the force is four times larger. · 将 $r$ 减半会使 $1/r^2$ 变为 $4$ 倍——力变为原来的四倍大。
Select all · 所有 changes that increase the electric force between two charges. · 选择所有能增加两个电荷之间静电力的变化。
$F = kq_1q_2/r^2$ grows with either charge and with closeness. Farther apart weakens it. · $F = kq_1q_2/r^2$ 随任一电荷的增加和距离的接近而增大。距离越远，力越弱。
Just like gravity, but stronger
- Coulomb's law has the same inverse-square shape as gravity.
- But the electric force is vastly stronger and can repel as well as attract.
- Gravity only ever pulls; the electric force does both, depending on the signs.
- This is why chemistry and electronics are governed by electric forces, not gravity.
就像引力,但更强
- 库仑定律与引力有相同的平方反比形式。
- 但电力强得多,而且既能相斥又能相吸。
- 引力永远只是拉;电力两者都能,取决于符号。
- 这就是为什么化学和电子学由电力而非引力支配。
Like gravity, the electric force follows an inverse-square law with distance. · 像重力一样，静电力遵循与距离平方成反比的定律。
Both $F = kq_1q_2/r^2$ and gravity go as $1/r^2$; the electric force can also repel. · 两者$F = kq_1q_2/r^2$和重力都遵循$1/r^2$；电力也可以排斥。
Coulomb's law is inverse-square ($1/r^2$), not $1/r$. Doubling the separation quarters the force, not halves it. And remember the force can be a push or a pull depending on whether the charges are alike or opposite.
库仑定律是平方反比($1/r^2$),而非 $1/r$。距离加倍使力变为四分之一,而非一半。并记住,力可以是推或拉,取决于电荷是同种还是异种。
Two charges are moved from $2\ \text{m}$ apart to $1\ \text{m}$ apart. How does the force change?
- Halving $r$ multiplies $\dfrac{1}{r^2}$ by $4$.
- The force becomes four times stronger.
两个电荷从相距 $2\ \text{m}$ 移到相距 $1\ \text{m}$。力如何变化?
- $r$ 减半使 $\dfrac{1}{r^2}$ 乘以 $4$。
- 力变为四倍强。
There are two kinds of charge (+ and −): like repel, opposite attract. Coulomb's law gives the force, $F = \dfrac{kq_1q_2}{r^2}$ — an inverse-square law like gravity, but far stronger and able to both attract and repel.
有两种电荷(+ 和 −):同种相斥、异种相吸。库仑定律给出力,$F = \dfrac{kq_1q_2}{r^2}$——一个像引力那样的平方反比定律,但强得多,并能既相吸又相斥。