Parallel Circuits: Current, Voltage and Resistance in Branches | 并联电路：支路中的电流、电压与电阻

📚 Parallel Circuits: Current, Voltage and Resistance in Branches | 并联电路：支路中的电流、电压与电阻

In a parallel circuit, components are connected side by side on separate branches. Each branch receives the full supply voltage, while the total current from the cell splits between the branches. This article explains the rules you need for KS3 CIE Electromagnets 1.2.2, including current, voltage, resistance and practical uses.

在并联电路中，元件并排连接在各自的支路上。每条支路都得到电源的全部电压，而电池流出的总电流在各支路之间分配。本文解释 KS3 CIE 电磁单元 1.2.2 并联电路所需的规则，包括电流、电压、电阻和实际应用。

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1. What Is a Parallel Circuit? | 什么是并联电路？

A parallel circuit is a circuit in which components are connected in separate branches between the same two points. This means there is more than one path for electric charge to flow. Each component forms its own loop with the cell.

并联电路是一种将元件连接在相同两个节点之间的独立支路中的电路。这意味着电荷有不只一条可流动的路径。每个元件与电池构成自己的回路。

The key feature of a parallel circuit is that each branch is independent. If you add or remove one branch, the other branches can still work. This is very different from a series circuit, where all components share one single loop.

并联电路的关键特点是每条支路相互独立。如果增加或移除一条支路，其他支路仍能工作。这与串联电路非常不同，在串联电路中所有元件共享一个回路。

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2. Building a Parallel Circuit | 搭建一个并联电路

To build a parallel circuit, connect two or more components so that each one has its own path between the positive and negative terminals of the cell. In a circuit diagram, parallel branches look like the rungs of a ladder connected between two main wires.

要搭建一个并联电路，需要连接两个或更多元件，使每个元件在电池正负极之间都有自己的路径。在电路图中，并联支路看起来像连接在两条主线之间的梯子横档。

For example, three lamps can be connected in parallel. One end of each lamp joins a common wire to the positive terminal. The other end of each lamp joins a common wire to the negative terminal. There are three separate loops, one for each lamp.

例如，可以将三个灯泡并联。每个灯泡的一端连接到通往正极的公共导线，每个灯泡的另一端连接到通往负极的公共导线。这样就有三个独立的回路，每个灯泡一个。

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3. Current Splits at Junctions | 电流在节点处分流

In a parallel circuit, the current from the cell reaches a junction and splits into the branches. The amount of current in each branch depends on the resistance of that branch. A branch with lower resistance carries more current.

在并联电路中，来自电池的电流到达节点后分流进入各支路。各支路中的电流大小取决于该支路的电阻。电阻较低的支路承载更多电流。

The total current supplied by the cell equals the sum of the currents in all the branches. This is written as Iₜ = I₁ + I₂ + I₃. The symbol I stands for current, measured in amperes (A).

电池提供的总电流等于所有支路电流之和。写作 Iₜ = I₁ + I₂ + I₃。符号 I 表示电流，单位是安培 (A)。

For example, if branch 1 carries 0.20 A, branch 2 carries 0.30 A and branch 3 carries 0.10 A, the cell current is 0.60 A. This rule is very useful for exam questions.

例如，如果支路 1 的电流为 0.20 A，支路 2 为 0.30 A，支路 3 为 0.10 A，那么电池电流为 0.60 A。这个规则对考试题很有用。

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4. Voltage Is the Same Across Each Branch | 各支路电压相同

In a parallel circuit, each branch is connected directly across the cell. Therefore, the voltage across every branch is equal to the supply voltage. If the cell is 6 V, then every branch has 6 V across it.

在并联电路中，每条支路都直接连接在电池两端。因此，每条支路两端的电压等于电源电压。如果电池是 6 V，那么每条支路的电压都是 6 V。

This can be written as Vₜ = V₁ = V₂ = V₃. Unlike current, voltage does not split. Each branch experiences the full push from the cell, even if the branches have different resistances.

这可以写作 Vₜ = V₁ = V₂ = V₃。与电流不同，电压不会分配。每条支路都得到电池的全部推动作用，即使各支路的电阻不同。

This explains why household appliances are connected in parallel. A lamp, a television and a kettle all receive the same mains voltage, and they work independently.

这解释了为什么家用电器采用并联连接。电灯、电视和水壶都获得相同的电源电压，并且独立工作。

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5. Resistance in Parallel: The Reciprocal Rule | 并联电阻：倒数规则

The total resistance of a parallel circuit is not found by simply adding the resistances. Instead, you add the reciprocals of the resistances. For two resistors, use 1/Rₜ = 1/R₁ + 1/R₂.

并联电路的总电阻不是简单地把电阻相加。相反，你需要把电阻的倒数相加。对于两个电阻，使用 1/Rₜ = 1/R₁ + 1/R₂。

For three or more resistors, extend the rule: 1/Rₜ = 1/R₁ + 1/R₂ + 1/R₃. After adding the reciprocals, take the reciprocal of the result to find Rₜ. The unit of resistance is the ohm (Ω).

对于三个或更多电阻，扩展该规则：1/Rₜ = 1/R₁ + 1/R₂ + 1/R₃。把倒数相加后，再取结果的倒数得到 Rₜ。电阻的单位是欧姆 (Ω)。

For two resistors only, there is a shortcut: Rₜ = (R₁ × R₂) ÷ (R₁ + R₂). This product-over-sum formula gives the same answer and saves time.

只有两个电阻时有一个捷径：Rₜ = (R₁ × R₂) ÷ (R₁ + R₂)。这个“乘积除以和”的公式给出相同答案，节省时间。

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6. More Branches, Lower Total Resistance | 支路越多，总电阻越小

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