📚 Static Electricity | 静电
Static electricity is the build-up of electric charge on the surface of an object. It is called 'static' because the charges stay in one place until they are discharged. In this topic, you will learn how static charge is produced, how charged objects behave, and why static electricity can be both useful and dangerous.
静电是物体表面积聚的电荷。之所以称为“静电”，是因为电荷会停留在原处，直到被释放。在本主题中，你将学习静电是如何产生的、带电物体如何相互作用，以及静电既有用又有危险的原因。
1. What Is Static Electricity? | 什么是静电？
Static electricity is an imbalance of electric charge on the surface of an object. When two different insulating materials are rubbed together, electrons can be transferred from one material to the other.
静电是物体表面电荷的不平衡。当两种不同的绝缘材料相互摩擦时，电子会从一种材料转移到另一种材料。
This produces one object with a positive charge and one object with a negative charge. The charges are stationary, so we call the effect static electricity.
这样就会使一个物体带正电，另一个物体带负电。由于电荷是静止的，我们称这种现象为静电。
2. Atoms and Electric Charge | 原子与电荷
All matter is made of atoms. An atom contains three types of particles: protons, neutrons and electrons.
所有物质都由原子组成。原子包含三种粒子：质子、中子和电子。
Protons have a positive charge (+), electrons have a negative charge (-), and neutrons have no charge. In a neutral atom, the number of protons equals the number of electrons.
质子带正电（+），电子带负电（-），中子不带电。在中性原子中，质子数等于电子数。
Only electrons can move from one atom to another during charging. Protons stay fixed inside the nucleus.
在起电过程中，只有电子能从一个原子转移到另一个原子。质子固定在原子核内，不能移动。
| Particle | Relative charge | Location |
|---|---|---|
| Proton | +1 | Nucleus |
| Neutron | 0 | Nucleus |
| Electron | −1 | Shells around the nucleus |
3. Conductors and Insulators | 导体与绝缘体
Materials that allow electrons to flow easily are called conductors. Metals such as copper and aluminium are good conductors because they have free electrons.
允许电子容易流动的材料称为导体。铜和铝等金属是良导体，因为它们有自由电子。
Materials that do not allow electrons to move easily are called insulators. Examples include plastic, rubber, glass and dry air.
不允许电子容易移动的材料称为绝缘体。例如塑料、橡胶、玻璃和干燥的空气。
Static charge builds up on insulators because electrons cannot flow away. On conductors, any extra charge quickly spreads out or escapes.
静电会积聚在绝缘体上，因为电子无法流走。在导体上，多余的电荷会迅速分散或流失。
4. Charging by Friction | 摩擦起电
Rubbing two insulators together can transfer electrons from one surface to another. The material that gains electrons becomes negatively charged; the material that loses electrons becomes positively charged.
将两种绝缘体相互摩擦，可以使电子从一个表面转移到另一个表面。得到电子的材料带负电；失去电子的材料带正电。
For example, when a polythene rod is rubbed with a dry cloth, electrons move from the cloth to the rod, so the rod becomes negatively charged.
例如，当用干布摩擦聚乙烯棒时，电子从布转移到棒上，因此棒带负电。
When an acetate rod is rubbed with a dry cloth, electrons move from the rod to the cloth, so the rod becomes positively charged.
当用干布摩擦醋酸纤维棒时，电子从棒转移到布上，因此棒带正电。
| Material rubbed | Charge transfer | Resulting charge |
|---|---|---|
| Polythene rod with dry cloth | Electrons move from cloth to rod | Rod becomes negative |
| Acetate rod with dry cloth | Electrons move from rod to cloth | Rod becomes positive |
| Balloon with dry hair | Electrons move from hair to balloon | Balloon becomes negative |
5. Like and Unlike Charges | 同种电荷与异种电荷
There are two types of electric charge: positive and negative. Objects with the same type of charge repel each other.
电荷有两种：正电荷和负电荷。带同种电荷的物体相互排斥。
Objects with opposite charges attract each other. This rule is often written as: like charges repel, unlike charges attract.
带异种电荷的物体相互吸引。这条规律通常写成：同种电荷相互排斥，异种电荷相互吸引。
You can test the charge on an object by bringing it close to a suspended charged rod. If the rod moves away, the charges are the same; if the rod moves towards the object, the charges are opposite.
你可以通过将物体靠近一个悬挂的带电棒来检验它的电荷。如果棒被推开，则电荷相同；如果棒被吸引，则电荷相反。
6. Attracting Uncharged Objects | 吸引不带电物体
A charged object can attract small uncharged objects, such as tiny pieces of paper or a thin stream of water. This happens because the charged object induces a separation of charge in the uncharged object.
带电物体能吸引不带电的小物体，如小纸片或细水流。这是因为带电物体使不带电物体内部发生电荷分离。
For example, a negatively charged balloon brought near a wall repels electrons in the wall surface, making that part of the wall slightly positive. The balloon then sticks to the wall by attraction.
例如，一个带负电的气球靠近墙壁时，会排斥墙表面的电子，使墙壁该部分略带正电。然后气球因吸引作用粘在墙上。
This is not because the uncharged object had a net charge; it is an induced effect.
这并不是因为不带电物体本身带有净电荷，而是一种感应效应。
7. Sparks and Static Discharge | 火花与静电放电
When enough charge builds up on an insulator, the charge can jump to a nearby conductor or to the ground. This sudden movement of electrons is called static discharge.
当绝缘体上积累足够多的电荷时，电荷会跳到附近的导体或地面上。这种电子的突然移动称为静电放电。
You may see a spark or hear a crackle when this happens. A lightning bolt is a very large natural example of static discharge between a cloud and the ground.
静电放电时，你可能会看到火花或听到噼啪声。闪电是云层与地面之间静电放电的一个非常大的自然例子。
The spark can transfer energy quickly, which may heat the air and produce light and sound.
火花会快速传递能量，使空气受热并产生光和声音。
8. Everyday Examples of Static Electricity | 日常生活中的静电现象
You may feel a small shock after walking across a carpet and then touching a metal door handle. Friction between your shoes and the carpet charges your body.
在地毯上行走后触摸金属门把手时，你可能会感到轻微电击。鞋子与地毯之间的摩擦使你的身体带电。
Clothes made of synthetic materials often cling together when removed from a tumble dryer because different items become oppositely charged.
合成材料衣物从烘干机取出后常会粘在一起，因为不同衣物带上了异种电荷。
A comb rubbed on dry hair can pick up small pieces of paper. The comb becomes charged and attracts the neutral paper.
用干头发摩擦梳子后，梳子能吸起小纸片。梳子带电后吸引中性纸片。
9. Dangers of Static Electricity | 静电的危害
Sparks from static electricity can ignite flammable gases, vapours or dust. This is dangerous in petrol stations, factories and flour mills.
静电产生的火花可能点燃易燃气体、蒸气或粉尘。这在加油站、工厂和面粉厂中非常危险。
Refuelling aircraft and vehicles requires careful earthing to prevent a spark from causing an explosion.
给飞机和车辆加油时需要小心接地，以防止火花引发爆炸。
Electronic components can also be damaged by static discharge. Workers handling circuit boards often wear earthing straps.
电子元件也可能被静电放电损坏。处理电路板的工作人员通常佩戴接地腕带。
10. Useful Applications of Static Electricity | 静电的利用
Static electricity is used in photocopiers and laser printers. A charged drum attracts toner particles to form the image before it is transferred to paper.
静电用于复印机和激光打印机。带电的感光鼓吸引墨粉颗粒，在转印到纸上之前形成图像。
Electrostatic precipitators in chimneys use charged plates to attract dust and smoke particles, reducing air pollution.
烟囱中的静电除尘器使用带电板吸引灰尘和烟雾颗粒，减少空气污染。
Spray painting cars can use static electricity: the paint particles and the car body are given opposite charges, so the paint is attracted evenly to the surface.
汽车喷漆可以利用静电：油漆颗粒和车身带上异种电荷，因此油漆被均匀地吸引到表面。
11. Electric Fields Around Charges | 电荷周围的电场
A charged object creates an electric field in the space around it. The field is the region where another charge feels a force.
带电物体在其周围空间产生电场。电场是另一个电荷会受到力的作用的区域。
The field lines point away from positive charges and towards negative charges. The closer the lines, the stronger the field.
电场线从正电荷出发并指向负电荷。电场线越密集，电场越强。
You cannot see an electric field, but its effects can be shown using charged objects or a small test charge.
你看不见电场，但可以通过带电物体或小的检验电荷来显示它的效应。
12. Key Points and Common Misconceptions | 要点与常见误区
Static electricity is caused by the transfer of electrons, not protons. Protons do not move during charging.
静电是由电子转移引起的，而不是质子转移。质子在起电过程中不会移动。
Insulators do not conduct charge, so they can hold static charge. Conductors allow charge to flow and are harder to charge by friction because the charge spreads.
绝缘体不导电，因此能保留静电。导体允许电荷流动，因此很难通过摩擦带电，因为电荷会扩散。
A charged object attracting a neutral object does not mean the neutral object had a charge. The charged object induces a temporary separation of charge.
带电物体吸引中性物体并不意味着中性物体带有电荷。带电物体只是使电荷发生了暂时的分离。
Static electricity can be both useful and dangerous. Understanding earthing and discharge helps us use it safely.
静电既有用又危险。理解接地和放电有助于我们安全地利用静电。
Published by TutorHao | Physics Revision Series | aleveler.com
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