热导体和绝热器

Do you like toast? Did you ever look inside a toaster while it’s toasting bread? When you push down the to turn on the toaster, the metal heating inside starts to glow orange or red almost instantly. You can see the glowing heating element inside this toaster. The glowing metal shows that the heating element has become very hot. It gets hot so quickly because are good conductors of .
::你喜欢烤面包吗?在烤面包的时候,你有没有看过烤面包机内的东西?当你推倒面包机打开面包机时,里面的金属加热几乎瞬间就开始发亮橙色或红色。你可以看到烤面包机内发光的加热元素。发光的金属显示加热元素已经变得非常热。它变得这么热,因为是好的导体。

Thermal Conductors
::热导体

is the transfer of thermal energy between particles of matter that are touching. Thermal conduction occurs when particles of warmer matter bump into particles of cooler matter and transfer some of their thermal energy to the cooler particles. Conduction is usually faster in certain solids and than in . Materials that are good conductors of thermal energy are called thermal conductors . Metals are especially good thermal conductors because they have freely moving electrons that can transfer thermal energy quickly and easily.
::热能是感应物质粒子之间的热能转移。当热物质粒子碰到冷却物质的粒子并将其部分热能转移到冷却颗粒时,就会发生热导。在某些固体中,导导速度通常比某些固体中快。热能的好导体材料被称为热导体。金属是特别好的热导体,因为它们可以自由移动能够迅速和容易地传输热能的电子。

Besides the heating element inside a toaster, another example of a thermal conductor is a metal radiator, like the one in the Figure . When hot water flows through the coils of the radiator, the metal quickly heats up by conduction and then radiates thermal energy into the surrounding air.
::除了烤面包机中的加热元件外,另一个热导体的例子就是金属散热器,如图中的金属散热器。当热水通过散热器的圈子流过热水时,金属会通过传导迅速加热,然后将热能散入周围空气。

Q: Thermal conductors have many uses, but sometimes it’s important to prevent the transfer of thermal energy. Can you think of an example?
::问题:热导体有许多用途,但有时重要的是防止热能的转移。你能想象一个例子吗?

A: One example is staying warm on a cold day. You will stay warmer if you can prevent the transfer of your own thermal energy to the outside air.
::一个例子是寒冷的天气保持温暖。如果你能防止自己的热能转移到外部空气中,你会保持温暖。

Thermal Insulators
::热绝热器

One way to retain your own thermal energy on a cold day is to wear clothes that trap air. That’s because air, like other gases, is a poor conductor of thermal energy. The particles of gases are relatively far apart, so they don’t bump into each other or into other things as often as the more closely spaced particles of liquids or solids. Therefore, particles of gases have fewer opportunities to transfer thermal energy. Materials that are poor thermal conductors are called thermal insulators . Down-filled snowsuits, like those in the Figure , are good thermal insulators because their feather filling traps a lot of air.
::在寒冷的日子里保持自己的热能的一种方法是穿戴束缚空气的衣服。 这是因为空气和其他气体一样,是热能的导体差。 气体的粒子相距相对较远,因此它们不会像液体或固体的近距离微粒那样频繁地相撞。 因此,气体的粒子转移热能的机会较少。 低热导体的材料被称为热导体。 下层雪花,像图中的那些,是很好的热导体,因为它们的羽毛充斥着大量的空气。

Another example of a thermal insulator is pictured in the Figure . The picture shows fluffy pink insulation inside the attic of a home. Like the down filling in a snowsuit, the insulation traps a lot of air. The insulation helps to prevent the transfer of thermal energy into the house on hot days and out of the house on cold days. Other materials that are thermal insulators include plastic and wood. That’s why pot handles and cooking utensils are often made of these materials. Notice that the outside of the toaster pictured in the opening image is made of plastic. The plastic casing helps prevent the transfer of thermal energy from the heating element inside to the outer surface of the toaster where it could cause burns. 
::热绝缘器的另一个例子可见于图中。图片显示了家庭阁楼内的粉色绝缘。像雪衣的下方填充物一样,绝缘器也有许多空气。隔热器有助于防止热日将热能转移到房屋,冷日则将热能转移到房屋外。其他热绝缘器材料包括塑料和木材。这就是为什么经常用这些材料制作锅柄和炊具的原因。注意开口图象中烤面包机外部是塑料的。塑料外壳有助于防止热能从热能元素转移到烤箱内可能燃烧的外表面。

Q: Thermal insulators have many practical uses besides the uses mentioned above. Can you think of others?
::问题:除上述用途外,热解器有许多实际用途。你能想到其他用途吗?

A: Thermal insulators are often used to keep food or drinks hot or cold. For example, Styrofoam® coolers and thermos containers are used for these purposes.
::A:热绝热器通常用于保持食物或饮用热或冷,例如,为此使用泡沫泡沫冷却器和热容器。

Summary
::摘要

播放段落
• Materials that are good conductors of thermal energy are called thermal conductors. Metals are very good thermal conductors.
  ::热能的好导体材料称为热导体,金属是非常好的热导体。
播放段落
• Materials that are poor conductors of thermal energy are called thermal insulators. Gases such as air and materials such as plastic and wood are thermal insulators.
  ::热能不良导体的材料称为热绝热器,气体如空气和塑料及木材等材料为热绝热器。

Review
::回顾

播放段落
1. What is a thermal conductor? Give an example.
   ::什么是热导体?
播放段落
2. Why do metals often feel cool to the touch?
   ::为什么金属通常会觉得触摸冷却?
播放段落
3. Define thermal insulator. Describe one way thermal insulators are used. 
   ::定义热绝缘器。 描述使用热绝缘器的一种方式 。