十万个为什么·科学启蒙30篇（4）

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为什么金属通常是导电的

Metals have a 'sea' of delocalized valence electrons that move freely among fixed positive metal ions.
When voltage is applied, these electrons drift directionally, carrying current with little resistance.
Crystalline structure matters: defects or impurities scatter electrons, increasing resistance and heating the wire.
Silver conducts best, followed by copper and gold—but copper is widely used for cost and stability reasons.
Alloys like brass conduct worse than pure metals because added atoms disrupt the electron flow path.
At low temperatures, some metals become superconductors—resistance drops to zero as electrons pair up and move smoothly.
Unlike insulators, whose electrons are tightly bound, metals require minimal energy to start current flow.
This electron mobility also explains why metals reflect light and feel cold—they transfer thermal energy efficiently too.

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When voltage is applied, these electrons drift directionally, carrying current with little resistance. 施加电压时，这些电子定向漂移，以极小电阻传导电流。
Crystalline structure matters: defects or impurities scatter electrons, increasing resistance and heating the wire. 晶体结构至关重要：缺陷或杂质会使电子散射，增大电阻并使导线发热。
Unlike insulators, whose electrons are tightly bound, metals require minimal energy to start current flow. 与电子被紧密束缚的绝缘体不同，金属只需极少能量即可启动电流。

这篇中文题目最接近哪一句？为什么金属通常是导电的一次学校运动会的通知一份超市购物清单

课文第一句的意思更接近？金属拥有由离域价电子构成的‘电子海’，这些电子在固定的正金属离子间自由移动。今天学校放假了。请把窗户打开。

这一课主要在讲什么？（看英文标题） Why Metals Conduct Electricity Well How to cook noodles A maths worksheet

When voltage is applied, these electrons drift directionally, carrying current with little resistance.

When voltage is applied, these electrons drift directionally, carrying current with little resistance.

第一版：录下来、回听、再听标准音。系统打分以后再加。

用今天的表达，自己说一句。

例子：When voltage is applied, these electrons drift directionally, carrying current with little resistance.