📚 Electromagnets Exam Question 1: Core Ideas and Model Answer | 电磁铁考试题 1：核心概念与标准答案
A typical KS3 CIE electromagnets Question 1 asks you to name a device made from a coil, an iron nail and a cell. It also asks you to give two ways to make the electromagnet stronger and to explain why soft iron is used as the core.
典型的 KS3 CIE 电磁铁第 1 题通常要求你说出由线圈、铁钉和电池组成的装置名称。题目还会要求你给出两种增强电磁铁的方法，并解释为什么铁芯使用软铁。
The mark scheme rewards precise scientific words: ‘electromagnet’, ‘soft iron core’, ‘increase the current’, and ‘add more turns of wire’. Vague answers such as ‘make it bigger’ or ‘use more electricity’ lose marks.
评分标准奖励准确科学用语：’电磁铁’、’软铁芯’、’增大电流’、’增加线圈匝数’。模糊答案如 ‘让它更大’ 或 ‘用更多电’ 会被扣分。
1. What the Question Is Testing | 题目考查点
This question checks whether you can link electricity and magnetism. You need to know the construction of an electromagnet, the role of the soft iron core, and how to make the magnetic field stronger.
这道题考查你是否能把电与磁联系起来。你需要知道电磁铁的结构、软铁芯的作用以及如何增强磁场。
A typical exam phrasing might be: ‘A student winds a coil of insulated wire around an iron nail and connects it to a cell. Name the device. Give two ways to make the device stronger. Explain why the iron nail is used.’
典型的考题表述可能是：’一名学生把绝缘导线绕在铁钉上并连接到电池上。说出这个装置的名称。给出两种使该装置更强的方法。解释为什么使用铁钉。’
The command words ‘name’, ‘give’ and ‘explain’ tell you how much detail to write. ‘Name’ needs one short answer, ‘give two ways’ needs two separate points, and ‘explain’ needs a scientific reason.
指令词 ‘name’、’give’ 和 ‘explain’ 告诉你需要写多少细节。’Name’ 需要一个简短答案，’give two ways’ 需要两个独立的点，’explain’ 需要一个科学原因。
2. Model Answer to Part (a): Naming the Device | 第 (a) 部分模型答案：设备命名
The device is an electromagnet. It is formed when a coil of insulated wire is wrapped around a soft iron core and connected to a cell.
这个装置是电磁铁。当绝缘导线绕在软铁芯上并连接到电池时，就构成了电磁铁。
An electromagnet is a temporary magnet. It only produces a magnetic field while current flows through the coil. When the switch is opened, the iron nail quickly loses most of its magnetism.
电磁铁是一种临时磁体。只有当电流通过线圈时，它才会产生磁场。当开关断开时，铁钉会迅速失去大部分磁性。
In a CIE-style mark scheme, the answer ‘electromagnet’ is enough for the naming part, but you can also write ‘a coil of wire around an iron core connected to a cell’ to show understanding.
在 CIE 风格的评分标准中，’电磁铁’ 这个答案足以应对命名部分，但你也可以写 ‘绕在铁芯上的线圈并连接到电池’ 来展示理解。
3. Why a Soft Iron Core Is Used | 为什么使用软铁芯
Soft iron is used because it is a soft magnetic material. It becomes magnetised easily when current flows and demagnetises quickly when current stops.
使用软铁是因为它是软磁性材料。它在电流通过时容易磁化，在电流停止时迅速退磁。
The iron core concentrates the magnetic field produced by the coil. This makes the field much stronger than the field from the coil alone.
铁芯会集中线圈产生的磁场。这使得磁场比仅有线圈时强得多。
A common exam answer: ‘The iron core focuses the magnetic field lines, increasing the overall strength.’ Do not write ‘iron conducts electricity’ because that is not the main reason here.
常见的考试答案：’铁芯集中磁感线，从而增大总强度。’ 不要写 ‘铁导电’，因为这并不是此处的主要原因。
If a question asks why soft iron rather than steel is used, add: ‘Steel would stay magnetised as a permanent magnet, but soft iron loses its magnetism when the current stops.’
如果题目问为什么使用软铁而不是钢，可以补充：’钢会保持磁性成为永久磁铁，而软铁在电流停止后会失去磁性。’
4. Two Ways to Increase the Strength | 增强电磁铁强度的两种方法
For the standard question, the two accepted ways are: increase the current through the coil, and increase the number of turns of wire around the iron core.
对于标准题目，两种可接受的方法是：增大通过线圈的电流，以及增加绕在铁芯上的线圈匝数。
A third valid method is to use a soft iron core, but since the iron nail is already present, examiners usually expect the other two methods for the ‘give two ways’ part.
第三种有效方法是使用软铁芯，但由于题目中已经给出了铁钉，阅卷人通常期望在 ‘给出两种方法’ 部分回答另外两种方法。
| Method | 方法 | Reason | 原因 |
|---|---|
| Increase the current | 增大电流 | Stronger magnetic field around the wire | 导线周围磁场更强 |
| Add more turns of wire | 增加线圈匝数 | Each turn adds to the total field | 每一匝都会增强总磁场 |
Remember to write these as two distinct points. If you write ‘increase current and add more turns’ as one sentence, it can still score both marks, but separating them makes it clear.
记住要把这两点写成两个独立的点。如果你把 ‘增大电流和增加匝数’ 写在一个句子里，仍然可以得两分，但分开写会更清晰。
5. Exam-Style Answer for Increasing Current | 关于增大电流的考试风格答案
Model sentence: ‘Increase the current flowing through the coil. This makes the magnetic field around each wire stronger, so the electromagnet can attract more magnetic materials.’
标准句式：’增大通过线圈的电流。这会使每根导线周围的磁场变强，因此电磁铁可以吸引更多磁性材料。’
Do not write ‘use more electricity’ or ‘turn up the cell’ without explaining that the current increases. Write ‘increase the current’ to match the mark scheme.
不要写 ‘用更多电’ 或 ‘调大电池’ 而不解释电流增大。要写 ‘增大电流’ 才能匹配评分标准。
If the question asks ‘explain why’, you need to link the larger current to a stronger magnetic field, not just say ‘it gets stronger’.
如果题目要求 ‘解释原因’，你需要把更大的电流与更强的磁场联系起来，而不仅仅是说 ‘它变强了’。
In an experiment, increasing the current means adding more cells in series or reducing resistance. However, be aware that very high current can overheat the wire.
在实验中，增大电流意味着串联更多电池或减小电阻。但要注意，过大的电流可能会使导线过热。
Published by TutorHao | KS3 Revision Series | aleveler.com
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