📚 Investigating Parallel Circuits (Electromagnets 1.2.2) | 并联电路实验探究（电磁学 1.2.2）
This practical investigation explores the fundamental behaviour of current, voltage, and resistance in parallel circuits, a core component of the Electromagnets 1.2.2 topic. Understanding how components share current and maintain equal voltage is essential for circuit analysis and design.
本实验探究并联电路中电流、电压和电阻的基本行为，这是电磁学 1.2.2 主题的核心内容。理解各元件如何分配电流并保持相等电压，对电路分析与设计至关重要。
1. Introduction to Parallel Circuits | 并联电路简介
In a parallel circuit, multiple paths exist for current to flow. Unlike series circuits, each branch is connected directly across the power supply, so every component receives the full source voltage. This arrangement is found in household wiring and many electronic devices.
在并联电路中，电流存在多条流动路径。与串联电路不同，每个支路都直接连接在电源两端，因此各元件均获得完整的电源电压。这种布局常见于家庭布线和许多电子设备中。
The key rules for parallel circuits are: total current equals the sum of branch currents; voltage is the same across all branches; and the reciprocal of total resistance equals the sum of the reciprocals of individual resistances.
并联电路的关键规律是：总电流等于各支路电流之和；各支路两端电压相等；总电阻的倒数等于各电阻倒数之和。
2. Aim of the Experiment | 实验目的
To investigate how current and voltage behave in a parallel circuit with two or more resistors, and to verify the relationship for equivalent resistance using experimental data.
探究由两个或多个电阻构成的并联电路中电流与电压的行为，并利用实验数据验证等效电阻的关系。
3. Apparatus | 实验器材
DC power supply (e.g., 3 V battery pack) | 直流电源（如3V电池组）
Two or three fixed resistors (e.g., 10 Ω, 22 Ω, 47 Ω) | 两到三个定值电阻（如10 Ω、22 Ω、47 Ω）
Voltmeter (or multimeter set to DC voltage) | 电压表（或设置为直流电压档的万用表）
Ammeter (or multimeter set to DC current) | 电流表（或设置为直流电流档的万用表）
Connecting leads and crocodile clips | 连接导线和鳄鱼夹
Switch (optional) | 开关（可选）
Breadboard for neat assembly | 面包板用于整洁组装
4. Circuit Diagram | 电路图
Draw a schematic diagram: a battery (V), a switch, an ammeter in series with the battery to measure total current, and two parallel branches each containing a resistor and its own ammeter to measure branch currents. A voltmeter is connected across the parallel network to measure the voltage across each resistor.
绘制原理图：电池（V），开关，一个与电池串联的电流表用于测量总电流，两条并联支路各包含一个电阻及其自身的电流表以测量支路电流。电压表并联在网络两端，测量每个电阻两端的电压。
Vsupply → [Atotal] → ┬──[R1]──[A1]──┐
└──[R2]──[A2]──┘ → back to battery
Voltmeter across the parallel branches: V1 = V2 = Vsupply
5. Procedure | 实验步骤
Set up the parallel circuit as shown in the diagram, initially using only R1 and R2. Leave one branch disconnected if you are using a switch for each branch to investigate adding resistors later. Ensure the ammeter is connected in series where you wish to measure current, and the voltmeter in parallel with the resistors.
按照图示搭建并联电路，最初仅使用 R1 和 R2。若每个支路配有开关，可先断开一个支路，以便后续增加电阻时探究。确保电流表串联在待测电流的位置，电压表与电阻并联。
Record the power supply voltage VS. For each branch, measure and note the current I1 and I2 through each resistor, and also the total current Itotal in the main part of the circuit. Measure the potential difference across each resistor (it should be equal to VS). Repeat the measurements after adding a third parallel resistor R3.
记录电源电压 VS。对于每个支路，测量并记录流过各电阻的电流 I1 和 I2，以及干路总电流 Itotal
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