磁铁

Lesson Objectives
::经验教训目标

• Identify properties of magnets.
  ::识别磁铁的特性。

• Explain why some materials are magnetic.
  ::解释为什么有些材料是磁材料。

• Explain that magnets can cause change without touching another object. 
  ::解释一下磁铁可以在不触碰另一个物体的情况下带来变化。

Lesson Vocabulary 
::词汇表课程

• magnet
  ::磁磁磁

Introduction
::导言

Take a look at this train in  Figure  . It looks very futuristic. What do you notice about it? Did you notice that the train has no wheels? How can a train have no wheels? It doesn't need wheels. It actually floats, or levitates, just above the track. Magnets enable the train to do this. This is not a normal train. This is a maglev train. The word "maglev" stands for "magnetic levitation." Because it has no wheels, there is no friction. Some magnets hold the train up. Other magnets are used to move the train forward. This train can go very fast. It can reach speeds up to 480 kilometers (300 miles) per hour! Magnets are pretty cool. What exactly is a magnet? How is it able to exert such force? 
::在图中查看这列列列车。它看起来非常未来。 你注意到什么了? 你注意到它没有轮子吗? 一列列列车怎么会没有轮子? 一列列列车怎么会没有轮子? 它不需要轮子? 它实际上没有轮子。 它会漂浮, 或浮起, 就在轨道上。 磁星使列车能够做到这一点。 这不是普通的列车。 这是一个磁列列列车。 “ 磁列车” 一词代表“ 磁列车 ” 。 因为它没有轮子, 没有摩擦 。 一些磁体将列车挂起来。 其它磁体用来将列车开到前面。 这列车可以非常快地前进。 它可以达到每小时480公里( 300英里)的速度! 磁列车是相当酷的。 磁体究竟是什么? 它是如何施加这种力量的?

 

Properties of Magnets
::Magnet 的属性

A  magnet  is an object that can attract other objects. You may have seen a bar magnet. If not, you can see one in  Figure  . Magnets have a north and south pole. Magnets only attract certain types of objects. They can attract objects that contain iron. Paper clips are made of iron and are attracted to magnets. Magnets do not attract every type of metal. Magnets only attract iron, nickel, and cobalt. Aluminum or copper are not attracted to magnets. Try this for yourself.  
::磁铁是一个可以吸引其它物体的物体。 您可能已经看到过一个磁铁磁铁。 如果不是的话, 您可以在图中看到。 Magnets 有北面和南面。 Magnets 只能吸引某些类型的物体。 它们可以吸引含有铁的物体。 纸片是由铁制成的, 被磁铁吸引。 Magnets 并不吸引每一种金属。 Magnets 只能吸引铁、 镍和钴。 铝或铜不会被磁铁吸引。 请自己试试 。

 

Magnetic Poles
::磁极

All magnets have two  magnetic poles . The poles are regions where the magnet is strongest. The poles are called north and south. They have these names because they always line up with Earth’s north-south axis. The Earth rotates, or spins, around this imaginary line, or axis. What do you suppose would happen if you cut the bar magnet in  Figure   in half along the line between the north and south poles? Both halves would also have north and south poles. What if you cut each of them in half again? That's right! All of those pieces would have north and south poles as well. Pieces of a magnet always have both north and south poles. 
::所有磁铁都有两个磁极。 电极是磁力最强的区域。 电极被称为北面和南面。 它们有这些名称, 因为它们总是与地球的南北轴相排。 地球绕着这个想象的线或轴旋转或旋转。 如果沿着北面和南面之间的线将条磁铁图一分为二, 你会有什么结果? 两半的电极也是北面和南面的。 如果你把两半的电极都切成两半呢? 没错! 所有这些电磁块都会有北面和南面。 磁铁的碎片总是有北面和南面的。

Magnetic Force
::磁力

Magnets are able to cause a change. They are able to make some other objects move. They do this by creating a force. This force is called a  magnetic force . There are different types of forces. Some forces require objects to touch. For example, you push a book across a table. You are touching the book as it moves. Think back on the levitating train. It wasn't touching the track. How could it move?
::Magnet 能够带来变化。 他们可以让一些其他对象移动。 他们通过创建一种力量来这样做。 这个力量被称为磁力。 有不同类型的力量。 有些力量需要触摸对象。 例如, 您将一本书推过一个表格。 您正在移动时触摸该书。 反省一下悬浮列车。 它没有触动轨道。 它如何移动 ?

Magnets too can produce change. They can produce motion just like you do. Unlike you, magnets do not need to touch the other object. That's right, there is a force without making contact. A magnetic force does not require objects to touch. A magnet can push or pull certain items without ever touching them. That's how the maglev train works.
::磁带也可以产生变化。 它们可以产生运动, 就像你一样。 不像你, 磁铁不需要触碰另一个物体。 没错, 磁力不需要触碰物体。 磁力不需要触碰物体。 磁力可以推动或拉动某些物品而无需触碰它们。 磁力列列车就是这样运作的 。

Do you know another type of force that does not require objects to touch? These forces are known as non-contact forces. Another type of non-contact force you may be familiar with is gravity. Gravity, too, can cause changes in motion. Gravity holds our Moon in orbit without touching it. So how do these forces play a role in magnets?
::您知道另一种不需要物体触碰的力量吗? 这些力量被称为非接触力量。 您可能熟悉的另一种非接触力量是引力。 重力也可以造成运动变化。 重力将我们的月球置于轨道上而没有触碰它。 那么这些力量如何在磁铁中发挥作用呢?

What happens when two magnets are next to each other? You know a force will be present. What type of motion do you think will occur? Will it be a push or a pull? It all depends on how the poles align. North and south poles of two magnets attract each other. Two north poles or two south poles repel each other. 
::当两块磁铁相邻时会怎样? 你知道会有一支力量存在。 你认为会发生哪种动作? 是推还是拉? 这都取决于两根电磁铁的对齐方式。 两根磁铁的北极和南极相互吸引。 两根北极或两根南极互相排斥。

Magnetism and Materials
::磁力和材料

You probably have magnets on your refrigerator. You can see some in  Figure  . You probably know they stick to a metal door. This might be what holds your homework up. Do magnets stick to all materials? Of course not. Magnets do not stick to many other surfaces. They do not stick to wooden doors. They do not stick to glass windows. What else can you find that they do not stick to?
::您的冰箱上可能有磁铁。 您在图中可以看到一些磁铁。 您可能知道它们会粘在金属门上。 这也许能支撑您的作业。 磁铁会粘在全部材料上吗? 当然不会。 磁铁不会粘在其他许多表面上, 它们不会粘在木门上, 它们不会粘在玻璃窗上。 您还能发现它们不粘在什么?

 

Lesson Summary
::经验教训摘要

• A magnet is an object that attracts certain materials, such as iron.
  ::磁铁是一种吸引铁等某些材料的物体。

• All magnets have two magnetic poles, north and south.
  ::所有磁铁都有两个磁极,北面和南面。

• Magnets have a magnetic field. It is this magnetic field that exerts a force on some materials.  Opposite magnetic poles attract each other. Like poles repel each other.
  ::磁磁场具有磁场。 磁场对某些材料产生一定的威力。 反面磁极相互吸引。 就像电杆互相击退一样 。

• Magnetism is the ability to be attracted by a magnet. Only some metals are attracted to magnets. These metals include: iron, cobalt, and nickel. When these materials are magnetized, they become temporary or permanent magnets. Magnetite is a natural permanent magnet.
  ::磁铁是被磁铁吸引的能力,只有某些金属被磁铁吸引。这些金属包括铁、钴和镍。当这些材料被磁化时,它们成为暂时或永久的磁铁。磁铁是一种天然的永久磁铁。

Lesson Review Questions
::经验回顾问题

Recall
::回顾

1. What is a magnet?
   ::什么是磁铁?

1. Give examples of objects that are attracted by magnets.
   ::举例说明磁铁吸引的物体。

Apply Concepts
::应用概念

3. Explain what type of motion will occur between the two magnets pictured below.
   ::解释一下在下面两块磁铁之间会发生什么样的运动。