📚 Charged Objects and Electric Fields | 带电物体与电场
When you rub a balloon on a wool jumper, the balloon can stick to a wall or make your hair stand up. These effects happen because objects can gain or lose electric charge, and a charged object creates an invisible electric field around it. In this topic, we explore how charged objects behave and how electric fields explain the forces we observe without contact.
当你用羊毛衫摩擦气球时，气球能贴在墙上，或让头发竖起来。这些现象发生是因为物体能获得或失去电荷，而带电物体周围会产生看不见的电场。本主题中，我们将研究带电物体如何表现，以及电场如何解释这些不接触就能产生的力。
1. Electric Charge | 电荷
All matter is made of atoms. An atom contains a central nucleus with protons and neutrons, and electrons moving around the nucleus. Protons carry positive charge, electrons carry negative charge, and neutrons have no charge.
所有物质都由原子组成。原子包含由质子和中子组成的中心原子核，以及围绕原子核运动的电子。质子带正电荷，电子带负电荷，中子不带电荷。
a charge of -1.6 × 10⁻¹⁹ C, and a proton has exactly the same size of charge but positive.
电荷的单位是库仑（C）。单个电子的电荷为 -1.6 × 10⁻¹⁹ C，质子的电荷大小完全相同，但符号为正。
Electron charge: e = -1.6 × 10⁻¹⁹ C
An object becomes negatively charged when it gains extra electrons, and positively charged when it loses electrons. Only electrons move; protons stay locked inside the nucleus.
物体获得额外电子时带负电，失去电子时带正电。只有电子会移动；质子被锁定在原子核内。
2. Positive and Negative Charge | 正电荷与负电荷
There are two types of electric charge: positive and negative. The simplest rule of electrostatics is that charges exert forces on each other.
电荷有两种类型：正电荷和负电荷。静电学最简单的规则是电荷之间会相互施加力。
Like charges repel each other. Two positive charges push apart, and two negative charges also push apart. Unlike charges attract each other: a positive and a negative charge pull together.
同种电荷相互排斥。两个正电荷互相推开，两个负电荷也互相推开。异种电荷相互吸引：一个正电荷和一个负电荷互相拉近。
- Positive + Positive: repel | 正 + 正：排斥
- Negative + Negative: repel | 负 + 负：排斥
- Positive + Negative: attract | 正 + 负：吸引
If an object has equal numbers of protons and electrons, its positive and negative charges cancel out, so the object is neutral.
如果一个物体拥有相同数量的质子和电子，它的正负电荷相互抵消，因此该物体呈电中性。
3. Charging by Friction | 摩擦起电
You can charge an insulator by rubbing it with a different material. The rubbing action transfers electrons from one surface to the other. No new charge is created; charge is only moved.
你可以通过用不同材料摩擦绝缘体来使其带电。摩擦作用使电子从一个表面转移到另一个表面。没有新的电荷被创造出来；电荷只是发生了转移。
For example, when a polythene rod is rubbed with a dry cloth, the rod gains electrons from the cloth, so the polythene rod becomes negatively charged. The cloth loses electrons, so it becomes positively charged.
例如，用干布摩擦聚乙烯棒时，聚乙烯棒从布上获得电子，因此聚乙烯棒带负电。布失去电子，因此带正电。
When an acetate rod is rubbed with a dry cloth, the rod loses electrons to the cloth. The acetate rod becomes positively charged, and the cloth becomes negatively charged.
用干布摩擦醋酸纤维棒时，醋酸纤维棒将电子转移给布。醋酸纤维棒带正电，布带负电。
Remember: positive charge does not move; only negative electrons move between surfaces.
请记住：正电荷不会移动；只有负电子在表面之间移动。
4. Conductors and Insulators | 导体和绝缘体
Materials can be divided into electrical conductors and insulators. Conductors, such as copper and other metals, allow electrons to move through them easily.
材料可分为电导体和绝缘体。导体（如铜和其他金属）允许电子在其中自由移动。
Insulators, such as plastic, rubber, glass and dry air, do not allow electrons to flow easily. Charge stays where it is placed on an insulator.
绝缘体（如塑料、橡胶、玻璃和干燥空气）不容易让电子流动。电荷会停留在绝缘体放置的位置上。
Only insulators can become charged by friction, because any charge produced on a conductor can flow away to Earth through your hand or the material itself.
只有绝缘体
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