📚 Series and Parallel Circuits: CIE KS3 Mark Scheme Guide | 串联与并联电路：CIE KS3 评分方案指南
This guide explains how CIE KS3 mark schemes award marks for series and parallel circuit questions. It covers the key words, accepted answers, common errors and the exact circuit rules you need to use in Checkpoint-style tests.
本指南解释 CIE KS3 评分方案如何对串联和并联电路题目给分。它涵盖关键词、可接受答案、常见错误以及在 Checkpoint 风格测试中你必须使用的电路规则。
1. What the Mark Scheme Rewards | 评分方案奖励什么
In CIE KS3 Science, circuit questions are marked for correct use of scientific ideas, not just for the final number. Marks are often given for stating that current is the same in series, that current splits in parallel, that voltage is shared in series, or that voltage is the same across parallel branches. The mark scheme also rewards correct circuit symbols, correct meter connections and clear comparative language when describing brightness.
在 CIE KS3 科学中，电路题考查的是对科学概念的正确使用，而不仅仅是最终数字。如果考生写出 "串联电流相同" "并联电流分流" "串联电压分配" 或 "并联支路两端电压相同"，通常就能得分。评分方案也奖励正确的电路符号、正确的电表连接方式以及描述亮度时使用清晰的比较性语言。
- Use the exact words "same current", "splits", "shared voltage", "same voltage" where appropriate. | 在适当位置使用 "电流相同" "分流" "电压分配" "电压相同" 等准确词语。
- Always compare brightness using "brighter than" or "dimmer than", not just "changes". | 描述亮度时始终用 "比……亮" 或 "比……暗"，而不是只说 "变化"。
- Circuit symbols must be drawn with straight lines and correct positions for ammeter and voltmeter. | 电路符号必须用直线绘制，电流表和电压表的位置要正确。
2. Current in Series Circuits | 串联电路中的电流
ings in series, you should write that A₁ = A₂ = A₃, so all the ammeter readings are equal.
在串联电路中，电荷只有一条回路可以流动。评分方案希望考生写出：串联电路各点的电流都相同。这是因为每秒通过每个元件的电荷数量相同。如果题目要求比较串联电路中两个电流表的读数，你应写出 A₁ = A₂ = A₃，即所有电流表读数相等。
I = I₁ = I₂ = I₃
A common mark scheme point is: "current is not used up by components". If a bulb is added in series, the current through every component decreases because the total resistance increases. This makes all bulbs dimmer.
常见的评分为："电流不会被元件消耗掉"。如果串联电路中再增加一个灯泡，由于总电阻增大，通过每个元件的电流都会减小，因此所有灯泡都会变暗。
3. Current in Parallel Circuits | 并联电路中的电流
In a parallel circuit, the current splits at junctions. The mark scheme usually gives a mark for saying that the total current from the cell equals the sum of the currents in the separate branches. For example, if branch 1 carries 0.3 A and branch 2 carries 0.2 A, the main circuit current is 0.5 A.
在并联电路中，电流在节点处分流。评分方案通常会给 "电池流出的总电流等于各支路电流之和" 这一点分数。例如，如果支路 1 的电流为 0.3 A，支路 2 的电流为 0.2 A，则干路电流为 0.5 A。
Itotal = I₁ + I₂ + I₃
You must avoid saying that the current "gets used up" or that all branches always have equal current. Branches only have equal current if their resistances are equal. The mark scheme penalises the statement "current is used up in the components" because current is conserved.
你必须避免说电流被 "用掉" 或所有支路的电流总是相等。只有在支路电阻相等时，各
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