📚 KS3 CIE Year 7 Electromagnets Scheme of Work | KS3 CIE 七年级电磁铁教学计划
This scheme of work introduces Year 7 learners to the key ideas of magnetism and electromagnetism within the Cambridge Lower Secondary science framework. Students will explore permanent magnets, magnetic fields, electromagnets and their practical uses through hands-on investigation and clear scientific language.
本教学计划在剑桥初中科学课程框架内，向七年级学生介绍磁学和电磁学的核心概念。学生将通过动手探究和清晰的科学语言，探索永磁体、磁场、电磁铁及其实际应用。
1. Magnets and Magnetic Materials | 磁铁与磁性材料
A magnet is an object that produces a magnetic field and attracts certain metals, especially iron, cobalt and nickel.
磁铁是能产生磁场并吸引某些金属的物体，尤其是铁、钴和镍。
Only a few metals are strongly magnetic at room temperature; most common metals such as copper, aluminium and zinc are not magnetic.
在室温下只有少数金属具有强磁性；大多数常见金属如铜、铝和锌都没有磁性。
An iron nail can become magnetised by stroking it many times in one direction with a permanent magnet.
铁钉可以用永磁体沿同一方向多次摩擦而被磁化。
Magnetised iron can be demagnetised by heating it, hammering it, or placing it inside a coil carrying alternating current.
磁化的铁可以通过加热、敲打或放在通有交流电的线圈中去磁。
2. Magnetic Poles and Forces | 磁极与磁力
Every magnet has two poles: the north-seeking pole (N) and the south-seeking pole (S).
每块磁铁都有两个磁极：指北极（N）和指南极（S）。
The magnetic force is strongest at the poles and weakest in the middle of the magnet.
磁力在两极处最强，在磁铁中间最弱。
Like poles repel each other, while unlike poles attract each other. This is the basic law of magnetism.
同名磁极相互排斥，异名磁极相互吸引。这是磁学的基本定律。
A freely suspended bar magnet always comes to rest pointing north-south because the Earth itself acts as a giant magnet.
一根自由悬挂的条形磁铁最终会指向南北方向，因为地球本身就像一个巨大的磁铁。
3. Magnetic Fields | 磁场
A magnetic field is the region around a magnet where a magnetic force can be detected. It is invisible but can be mapped.
磁场是磁铁周围能够检测到磁力的区域。磁场虽然看不见，但可以描绘出来。
Field lines are used to show the direction and strength of a magnetic field. They point from the north pole to the south pole outside the magnet.
磁感线用来表示磁场的方向和强度。在磁铁外部，磁感线从北极指向南极。
Iron filings sprinkled around a bar magnet line up along the field lines, revealing the pattern of the magnetic field.
在条形磁铁周围撒上铁屑，铁屑会沿磁感线排列，显示出磁场的分布。
A plotting compass can also trace field lines because its needle lines up with the local direction of the magnetic field.
小磁针也可以描绘磁感线，因为磁针会与所在位置的磁场方向对齐。
4. Electromagnetism: Current Creates Magnetism | 电磁学：电流生磁
When an electric current flows through a straight wire, a weak magnetic field is produced around the wire.
当电流通过直导线时，导线周围会产生一个微弱的磁场。
Winding the wire into a coil called a solenoid concentrates the magnetic field inside the coil, making it much stronger.
将导线绕成称为螺线管的线圈可以集中线圈内部的磁场，使磁场大大增强。
Placing a soft iron core inside the solenoid increases the magnetic field further because iron is a ferromagnetic material.
在螺线管内部放入软铁芯可以进一步增强磁场，因为铁是一种铁磁材料。
This combination of a coil and an iron core is called an electromagnet, and it behaves like a magnet only when current is flowing.
线圈和铁芯的组合称为电磁铁，只有在电流通过时它才像磁铁一样工作。
5. Building an Electromagnet | 制作电磁铁
An electromagnet is constructed by wrapping insulated copper wire around a soft iron core in a tight coil.
电磁铁由绝缘铜线紧密绕制在软铁芯上构成。
The wire is insulated so that the current can flow around every turn of the coil without short-circuiting between turns.
导线有绝缘层，以便电流能流过线圈的每一匝，而不会在匝间发生短路。
When the current is switched on, the soft iron core becomes magnetised and the electromagnet can attract magnetic materials.
当电流接通时，软铁芯被磁化，电磁铁就能吸引磁性材料。
When the current is switched off, the soft iron core quickly loses most of its magnetism, so the electromagnet releases the objects.
当电流断开时，软铁芯迅速失去大部分磁性，因此电磁铁会释放物体。
6. Factors Affecting Electromagnet Strength | 影响电磁铁强度的因素
The strength of an electromagnet can be increased by increasing the electric current through the coil.
通过增大线圈中的电流可以增强电磁铁的强度。
Adding more turns of wire to the coil also increases the magnetic field strength because each turn contributes to the total field.
增加线圈的匝数也会增强磁场强度，因为每一匝都会对总磁场作出贡献。
Using a larger or more permeable soft iron core can make the electromagnet stronger by concentrating the field more effectively.
使用更大或磁导率更高的软铁芯可以更有效地集中磁场，从而使电磁铁更强。
In an investigation, changing more than one of these factors at the same time would make it difficult to tell which factor caused the change in strength.
在探究实验中，如果同时改变多个因素，就很难判断是哪个因素导致了强度的变化。
7. Investigating Electromagnets | 探究电磁铁实验
A common Year 7 investigation measures the number of paper clips an electromagnet can pick up when the number of coil turns is changed.
七年级常见的探究实验是改变线圈匝数，测量电磁铁能吸起多少枚回形针。
The independent variable is the number of coil turns, and the dependent variable is the number of paper clips attracted.
自变量是线圈匝数，因变量是吸引的回形针数量。
Control variables such as the current, the type of core and the size of the paper clips must be kept the same for a fair test.
控制变量（如电流大小、铁芯类型和回形针尺寸）必须保持不变，以确保
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