📚 Series Circuits | 串联电路
In a series circuit, components are joined in one single loop. The current has only one path to follow, so the same current passes through every component. This simple idea helps explain how current, voltage and resistance behave in series.
在串联电路中，元件连接在单一回路中。电流只有一条路径可走，因此同一个电流通过每个元件。这个简单的概念有助于解释串联电路中电流、电压和电阻的行为。
1. What is a Series Circuit? | 什么是串联电路？
A series circuit is a closed circuit with only one conducting path. The components are connected end-to-end, so they share the same current.
串联电路是只有一条导电通路的闭合电路。元件首尾相连，因此它们共享同一电流。
If any part of a series circuit is broken or disconnected, the current stops everywhere. This is why old string lights went out completely when one bulb failed.
如果串联电路的任何一部分断开或脱落，所有地方的电流都会停止。这就是为什么老式灯串在一个灯泡损坏时会全部熄灭。
2. Drawing and Building a Series Circuit | 绘制和搭建串联电路
A simple series circuit can contain a cell, a switch, a lamp and an ammeter connected in one closed loop. When drawing circuit diagrams, use standard symbols and straight wires.
一个简单的串联电路可以包含电池、开关、灯泡和电流表，它们连接在一个闭合回路中。绘制电路图时，要使用标准符号和直线导线。
The ammeter must be placed in series with the component, meaning it is part of the same loop. A voltmeter is placed in parallel across the component being tested.
电流表必须与元件串联，即它是同一回路的一部分。电压表则与被测元件并联。
3. Current in a Series Circuit | 串联电路中的电流
In a series circuit, the current is the same at every point. This is because there is only one path for charge to flow through.
在串联电路中，电流处处相同。这是因为电荷只有一条流动路径。
If you place ammeters at different positions in the same series circuit, they all show the same reading.
如果在同一个串联电路的不同位置放置电流表，它们的读数都相同。
I₁ = I₂ = I₃
Here I₁, I₂ and I₃ are the currents at three different points in the loop.
这里的 I₁、I₂ 和 I₃ 是回路中三个不同点的电流。
4. Voltage in a Series Circuit | 串联电路中的电压
The supply voltage is shared between the components in a series circuit. The total voltage from the cell equals the sum of the voltages across all components.
在串联电路中，电源电压在元件之间分配。电池提供的总电压等于所有元件电压之和。
Vₜₒₜₐₗ = V₁ + V₂ + V₃
For example, if a 6 V cell is connected to two identical bulbs in series, each bulb receives 3 V, provided the bulbs are identical.
例如，如果 6 V 电池与两个相同灯泡串联，每个灯泡得到 3 V（前提是灯泡完全相同）。
5. Resistance in a Series Circuit | 串联电路中的电阻
Adding more resistors or bulbs in series increases the total resistance. The total resistance is the sum of all individual resistances.
在串联电路中增加更多电阻或灯泡会增大总电阻。总电阻等于所有单个电阻之和。
Rₜₒₜₐₗ = R₁ + R₂ + R₃
Higher total resistance reduces the current, because current depends on voltage divided by resistance.
总电阻增大会使电流减小，因为电流等于电压除以电阻。
6. Brightness of Bulbs in Series | 串联灯泡的亮度
In a series circuit, bulbs share the total voltage. Adding more bulbs means each bulb receives a smaller share, so each bulb becomes dimmer.
在串联电路中，灯泡分担总电压。增加更多灯泡意味着每个灯泡分到的电压更少，因此每个灯泡都会变暗。
If identical bulbs are connected in series, they have the same brightness. The brightness depends on the power or energy transferred per second, which is affected by both current and voltage.
如果相同的灯泡串联，它们的亮度相同。亮度取决于每秒传递的功率或能量，这与电流和电压都有关。
7. Switches in a Series Circuit | 串联电路中的开关
A single switch in a series circuit controls all components at the same time. When the switch is open, the loop is broken and no current flows anywhere.
串联电路中的一个开关同时控制所有元件。当开关断开时，回路被切断，任何地方都没有电流。
When the switch is closed, the circuit is complete and current flows through every component in the loop.
当开关闭合时，电路形成完整回路，电流流过回路中的每一个元件。
8. Advantages and Disadvantages of Series Circuits | 串联电路的优点与缺点
A series circuit is simple to build and makes it easy to measure current at one point. However, if one component fails, the whole circuit stops working.
串联电路结构简单，便于在某一点测量电流。然而，如果一个元件损坏，整个电路都会停止工作。
Another disadvantage is that adding more bulbs makes all bulbs dimmer, which is not ideal for lighting circuits. In practice, most home lighting uses parallel circuits.
另一个缺点是增加更多灯泡会使所有灯泡变暗，这对照明电路并不理想。实际上，大多数家庭照明使用并联电路。
9. Fault Finding in Series Circuits | 串联电路故障排查
If a series circuit stops working, check for an open switch, a broken bulb, a disconnected wire or a flat cell. An open circuit has no current.
如果串联电路停止工作，检查开关是否断开、灯泡是否损坏、导线是否脱落或电池是否没电。开路中没有电流。
To identify a faulty bulb, replace each bulb one at a time with a known working bulb. If the circuit lights up again, the removed bulb was the fault.
要找出损坏的灯泡，可以用一个确认完好的灯泡逐一替换。如果电路重新亮起，被替换下来的灯泡就是故障所在。
10. Series vs Parallel Circuits | 串联电路与并联电路对比
In a series circuit, current is the same everywhere and voltage splits between components. In a parallel circuit, current splits between branches and voltage is the same across each branch.
在串联电路中，电流处处相同，电压在元件之间分配。在并联电路中，电流在支路之间分流，各支路两端电压相同。
A parallel circuit has the advantage that one broken branch does not stop the other branches. In series, one break stops the entire circuit.
并联电路的优点是一条支路损坏不会影响其他支路。而在串联电路中，一处断开会使整个电路停止。
11. Worked Example | 例题
A 6 V cell is connected to two identical bulbs in series. Calculate the voltage across each bulb.
一个 6 V 电池与两个相同的灯泡串联。计算每个灯泡两端的电压。
V₁ = V₂ = 6 V ÷ 2 = 3 V
Each bulb receives 3 V because the total voltage is shared equally between identical bulbs.
每个灯泡得到 3 V，因为总电压在相同灯泡之间平均分配。
If three resistors in series have a total resistance of 15 Ω, and two of them are 4 Ω and 5 Ω, calculate the third resistance.
如果三个电阻串联的总电阻为 15 Ω，其中两个电阻分别为 4 Ω 和 5 Ω，计算第三个电阻值。
Rₜₒₜₐₗ = R₁ + R₂ + R₃ → 15 Ω = 4 Ω + 5 Ω + R₃ → R₃ = 6 Ω
The third resistor must be 6 Ω because total resistance is the sum of all three resistances.
第三个电阻必然为 6 Ω，因为总电阻等于三个电阻之和。
12. Key Summary and Exam Tips | 关键总结与考试技巧
In series: one loop, same current, shared voltage, total resistance = sum of resistances. Use an ammeter in series and a voltmeter in parallel.
串联电路：一个回路，电流相同，电压分配，总电阻等于电阻之和。电流表串联使用，电压表并联使用。
Exam tip: when asked about series circuits, always mention that current is the same at all points and voltage is
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