Electric Fields · 电场
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| electric field/ɪˈlektrɪk fiːld/ | 电场 | diàn chǎng |
A charge feels a push with nothing touching it
- Hold a charge near another and it feels a force — across empty space, nothing in between.
- How? Each charge fills the space around it with an invisible electric field 电场.
- Any charge placed in that field feels a force from it.
- The field is the "reach" of a charge, mapped out everywhere around it.
电荷不接触任何东西也会感到推力
- 把一个电荷靠近另一个,它会感到力——跨过真空,中间什么也没有。
- 怎么做到的?每个电荷用一个看不见的电场充满它周围的空间。
- 放进那个场里的任何电荷都会感到来自它的力。
- 场是电荷的"触及范围",在它周围处处被描绘出来。
Field is force per charge
- The electric field $E$ is the force per unit charge: $E = \dfrac{F}{q}$.
- Its units are $\tfrac{\text{N}}{\text{C}}$, and it is a vector with a direction at every point.
- Put a charge $q$ in a field $E$ and it feels a force $F = qE$.
- The field exists whether or not a test charge is there to feel it.
场是单位电荷所受的力
- 电场 $E$ 是单位电荷所受的力:$E = \dfrac{F}{q}$。
- 它的单位是 $\tfrac{\text{N}}{\text{C}}$,是一个矢量,在每一点都有方向。
- 把电荷 $q$ 放进场 $E$,它感到力 $F = qE$。
- 无论有没有试探电荷去感受它,场都存在。
Map the field · 绘制场线图
Change the charge's sign and size and watch the field lines flip and thicken. · 改变电荷的符号和大小，观察电场线翻转并变密。
A $2\ \text{C}$ charge sits in a field of $5\ \tfrac{\text{N}}{\text{C}}$. What force does it feel, in $\text{N}$? · 一个$2\ \text{C}$电荷处于$5\ \tfrac{\text{N}}{\text{C}}$的电场中。它受到的力是多少，单位为$\text{N}$？
$F = qE = 2 \times 5 = 10\ \text{N}$.
The electric field at a point is defined as: · 某点的电场强度定义为：
$E = F/q$ — the force a unit positive charge would feel. · $E = F/q$ — 单位正电荷将感受到的力。
Reading field lines
- Field lines show the field's direction: they point the way a positive test charge would be pushed.
- They point away from positive charges and toward negative charges.
- Where lines are closer together, the field is stronger.
- Lines never cross — the field has one direction at each point.
读场线
- 场线显示场的方向:它们指向正试探电荷会被推去的方向。
- 它们背离正电荷、指向负电荷。
- 场线越密集的地方,场越强。
- 场线绝不相交——场在每一点只有一个方向。
Electric field lines point: · 电场线指向：
Lines show where a positive test charge is pushed: away from + and toward −. · 线条显示正试探电荷被推的方向：远离+，朝向−。
Where the field lines are closer together, the field is . · 电场线越密集的地方，电场越。
Denser lines mean a stronger field. · 线条越密表示电场越强。
Select all · 所有 true statements about electric field lines. · 选择所有关于电场线的正确陈述。
Lines run + → − and crowd where the field is strong. They never cross. · 线条从+到−延伸，在电场强处密集。它们永不相交。
The field of a point charge
- A single point charge makes a field $E = \dfrac{kq}{r^2}$ pointing radially outward (if +).
- It weakens with the inverse square of distance, just like the force.
- Near the charge the field is intense; far away it fades.
- Combine several charges by adding their field vectors at each point.
点电荷的场
- 单个点电荷产生场 $E = \dfrac{kq}{r^2}$,沿半径向外(若为 +)。
- 它按距离的平方反比减弱,就像力一样。
- 在电荷附近场很强;远处则消退。
- 把几个电荷合起来,就在每一点相加它们的场矢量。
An electric field exists around a charge even when no test charge is present. · 即使没有试探电荷存在，电荷周围也存在电场。
The source charge sets up the field; a test charge only reveals it. · 源电荷建立电场；试探电荷仅用于揭示其存在。
The field $E$ exists on its own, set by the source charges — it is there even with no test charge present. And field lines point the way a positive charge would move: away from +, toward −. A negative charge feels a force opposite to the field.
场 $E$ 自身存在,由源电荷决定——即便没有试探电荷也在那里。而且场线指向正电荷会移动的方向:背离 +、指向 −。负电荷所受的力与场相反。
A charge of $q = 2\ \text{C}$ sits in a field of $E = 5\ \tfrac{\text{N}}{\text{C}}$. What force does it feel?
- $F = qE = 2 \times 5 = 10\ \text{N}$, in the direction of the field.
A negative charge of the same size would feel $10\ \text{N}$ the opposite way.
一个 $q = 2\ \text{C}$ 的电荷处于 $E = 5\ \tfrac{\text{N}}{\text{C}}$ 的场中。它感到多大的力?
- $F = qE = 2 \times 5 = 10\ \text{N}$,沿场的方向。
同样大小的负电荷会感到 $10\ \text{N}$ 反方向的力。
An electric field $E = F/q$ (in $\tfrac{\text{N}}{\text{C}}$) is the force per unit charge that surrounds every charge; a charge in it feels $F = qE$. Field lines point away from + and toward −, and are denser where the field is stronger. A point charge gives $E = kq/r^2$.
电场 $E = F/q$(单位 $\tfrac{\text{N}}{\text{C}}$)是环绕每个电荷的单位电荷所受的力;其中的电荷感到 $F = qE$。场线背离 +、指向 −,场越强越密。点电荷给出 $E = kq/r^2$。