Electromagnets 1.2.1 – Series Circuits Investigation | 电磁铁 1.2.1 串联电路实验探究

📚 Electromagnets 1.2.1 – Series Circuits Investigation | 电磁铁 1.2.1 串联电路实验探究

This investigation explores the fundamental behaviour of series circuits by using electromagnets as the load components. By connecting two iron-core solenoids in series, you can measure current, voltage, and resistance, then verify the core rules of series connections. The experiment also demonstrates how the strength of an electromagnet depends on the current flowing through it, linking circuit theory directly to magnetism.

本实验探究通过使用电磁铁作为负载元件，探索串联电路的基本行为。将两个铁芯螺线管串联连接，你可以测量电流、电压和电阻，从而验证串联连接的核心规则。该实验还演示了电磁铁的磁性强弱如何依赖于通过它的电流大小，将电路理论与磁性直接联系起来。

1. Electromagnets and Series Circuits | 电磁铁与串联电路

An electromagnet consists of a coil of insulated copper wire wound around a soft iron core. When current passes through the coil, it produces a magnetic field. In a series circuit, the same current flows through every component because there is only one path for charge. This property makes series circuits ideal for controlling multiple electromagnets with identical current, such as in relays, cranes, or electric bells.

电磁铁由绕在软铁芯上的绝缘铜线圈组成。当电流通过线圈时，它会产生磁场。在串联电路中，由于只有一条电荷通路，相同的电流流过每一个元件。这一性质使串联电路非常适合用相同电流控制多个电磁铁，例如继电器、起重机或电铃中的应用。

2. Learning Objectives | 学习目标

By the end of this investigation you should be able to: set up a series circuit with two electromagnets; measure current and potential difference using ammeters and voltmeters; verify that current is the same at all points; demonstrate that the sum of individual p.d.s equals the supply p.d.; calculate total resistance; and relate changes in current to the magnetic strength of an electromagnet.

通过本次探究，你应能做到：搭建含两个电磁铁的串联电路；使用电流表和电压表测量电流和电势差；验证电路中各点电流相同；证明各元件电势差之和等于电源电势差；计算总电阻；并将电流变化与电磁铁的磁性强弱联系起来。

3. Apparatus for the Investigation | 实验器材

The following equipment is needed: a d.c. power supply (0–6 V variable), two identical laboratory electromagnets (each 200–400 turns of copper wire on an iron core), a single-throw switch, a variable resistor (rheostat, 0–10 Ω), three digital multimeters (or an ammeter plus two voltmeters), connecting leads with crocodile clips, a small quantity of paper clips or iron filings to test magnetic strength, and a ruler.

需要以下器材：直流电源（0–6 V可调），两个相同的实验室电磁铁（每个铁芯上绕200–400匝铜线），单刀开关，可变电阻器（滑线变阻器，0–10 Ω），三块数字万用表（或一块电流表加两块电压表），鳄鱼夹导线，少量回形针或铁屑用于测试磁性强度，以及一把直尺。

4. Constructing the Series Circuit with Electromagnets | 搭建电磁铁串联电路

Connect the positive terminal of the power supply to one end of the rheostat. From the rheostat, wire to one terminal of the switch. After the switch, connect the first electromagnet, then the second electromagnet, and finally return to the negative terminal of the power supply. The ammeter must be inserted in series at any point – it is convenient to place it between the switch and the first electromagnet. Voltmeters are connected in parallel across the whole supply and across each electromagnet separately.

将电源正极连接到滑线变阻器的一端。从变阻器接线到开关的一个接线柱。开关之后，串联第一个电磁铁，再串联第二个电磁铁，最后回到电源负极。电流表必须串联在电路中的任意一点——方便的做法是将它接在开关和第一个电磁铁之间。电压表分别并联在整个电源两端以及每个电磁铁的两端。

Circuit layout: + → Rheostat → Switch → Ammeter → Electromagnet 1 → Electromagnet 2 → – (Supply)

电路布局：正极 → 变阻器 → 开关 → 电流表 → 电磁铁1 → 电磁铁2 → 负极（电源）

5. Measuring Current along the Series Path | 沿串联路径测量电流

Close the switch and adjust the rheostat to obtain a moderate current (0.2–0.5 A). Record the ammeter reading. Then, without altering the circuit, move the ammeter to different positions: between the two electromagnets, and after the second electromagnet. According to series circuit rules, the current should be identical at every location. Compare the three readings.

闭合开关，调节变阻器获得适中的电流（0.2–0.5 A）。记录电流表读数。然后，在不改变电路的情况下，将电流表移到不同位置：两个电磁铁之间，以及第二个电磁铁之后。根据串联电路规则，电流在各位置应完全相同。比较三组读数。

You may observe a tiny variation due to meter internal resistance, but within experimental uncertainty the current remains constant: I_total = I₁ = I₂ = I₃.

由于电表内阻，你可能会观察到微小变化，但在实验误差范围内电流保持恒定：I_total = I₁ = I₂ = I₃。

6. Measuring Voltage across Components | 测量各元件两端的电压

With the ammeter returned to a fixed position, connect voltmeter V₁ across the two terminals of electromagnet 1, and voltmeter V₂ across electromagnet 2. Use a third voltmeter (or reconnect the same one) to measure the total supply voltage V_total across the power source. Record all three values for a given rheostat setting.

将电流表放回某固定位置后，把电压表 V₁ 接在电磁铁1的两个接线端，V₂ 接在电磁铁2两端。用第三块电压表（或同一块表重新连接）测量电源两端的总电压 V_total。在某个变阻器设定下记录这三个数值。

Repeat the measurements for at least five different rheostat positions. Each time, check whether V_total = V₁ + V₂. The small energy lost in connecting wires may cause a slight discrepancy, but the sum of the individual p.d.s should approximately equal the supply voltage.

在至少五个不同变阻器位置重复上述测量。每次检查是否满足 V_total = V₁ + V₂。导线上的微小能量损耗可能导致轻微偏差，但各元件电势差之和应近似等于电源电压。

7. Observing Electromagnet Strength Variation | 观察电磁铁强度的变化

Electromagnet strength is often demonstrated by counting how many paper clips the core can attract when the circuit is energised. At each rheostat setting, bring a small pile of paper clips close to one pole of electromagnet 1; record the maximum number lifted. Do the same for electromagnet 2. Because the same current flows through both coils, they should exhibit similar lifting power if the coils are identical.

电磁铁的强度通常通过通电时铁芯能吸引多少个回形针来演示。在每个变阻器设定下，将一小堆回形针靠近电磁铁1的一极，记录能吸起的最多数量。对电磁铁2做同样的测试。由于两个线圈流过的电流相同，如果线圈相同，它们应表现出相似的吸引能力。

As current increases, the magnetic field becomes stronger, and more paper clips are attracted. You can qualitatively link the current reading to magnetic strength: magnetic flux density B ∝ I (for a fixed number of turns).

随着电流增大，磁场变强，能吸引更多回形针。你可以定性地将电流读数与磁性强弱联系起来：对于固定匝数，磁通密度 B ∝ I（电流越大，磁场越强）。

8. Data Recording and Analysis | 数据记录与分析

Organise your measurements in a table similar to the one below. Calculate total resistance R_total = V_total / I, as well as individual resistances R₁ = V₁ / I and R₂ = V₂ / I. Check that R_total ≈ R₁ + R₂ for every trial.

将你的测量数据整理成类似下表的表格。计算总电阻 R_total = V_total / I，以及各个电阻 R₁ = V₁ / I 和 R₂ = V₂ / I。检验每次试验是否满足 R_total ≈ R₁ + R₂。

I (A)	V1 (V)	V2 (V)	Vtotal (V)	R1 (Ω)	R2 (Ω)	Rtotal (Ω)	Paper clips (EM1)
0.22	1.10	1.12	2.24	5.00	5.09	10.18	3
0.30	1.48	1.50	3.01	4.93	5.00	10.03	5

Plot a graph of V_total against I. The gradient gives the total resistance of the circuit. In a series arrangement, the total resistance is simply the sum of the individual resistances of the electromagnets and any rheostat section in series.

绘制 V_total 随 I 变化的图形。斜率给出电路的总电阻。在串联结构中，总电阻就是电磁铁电阻与串联变阻器部分电阻之和。

9. Verifying Ohm’s Law in an Electromagnet Circuit | 验证电磁铁电路中的欧姆定律

The copper windings of an electromagnet are ohmic conductors under steady temperature. That means the ratio V/I remains constant for each coil when the temperature does not change significantly. During rapid measurements, the coils stay cool, so you should obtain a linear I–V relationship for each electromagnet and for the whole series combination.

电磁铁的铜绕组在温度稳定时是欧姆导体。这意味着当温度没有显著变化时，每个线圈的 V/I 比值保持恒定。在快速测量过程中，线圈保持低温，因此每个电磁铁以及整个串联组合应呈现线性的 I–V 关系。

If you allow current to flow for a long time, the coils warm up, their resistance increases slightly, and the graph deviates from a perfect straight line. This heating effect is a useful discussion point when evaluating the reliability of the results.

如果让电流长时间流过，线圈会发热，电阻略有增加，图形会偏离完美的直线。这种热效应是评估结果可靠性时的一个有用讨论点。

10. Safety Precautions | 安全注意事项

Keep the current below the maximum rating of the electromagnets (usually ≤ 1 A) to prevent overheating. Always switch off the circuit when not taking readings, especially while moving meters or handling paper clips. The iron cores of electromagnets may become slightly warm; allow them to cool between trials. Ensure all connections are tight to avoid sparking.

保持电流低于电磁铁的最大额定值（通常 ≤ 1 A）以防过热。在不读数时务必断开电路，特别是在移动电表或操作回形针时。电磁铁的铁芯可能会略微发热；在各次试验之间让其冷却。确保所有连接牢固，避免产生火花。

11. Sources of Error and Improvements | 误差来源与改进

Systematic errors arise from the internal resistance of ammeters and voltmeters. An ideal ammeter has zero resistance, while a real one adds a small series resistance, slightly reducing the circuit current. Voltmeters draw a tiny current, which can affect the p.d. reading when measuring across high-resistance components. Use digital multimeters with high input impedance to minimise this effect.

系统误差来源于电流表和电压表的内阻。理想电流表的电阻为零，而实际电流表会引入小的串联电阻，略微减小电路电流。电压表会分流极小的电流，这可能在测量高阻元件两端的电势差时影响读数。使用高输入阻抗的数字万用表可尽量减小这种影响。

Random errors can occur when counting paper clips or reading analogue scales. To improve reliability, repeat each measurement three times and use the mean value. Also, keep the iron core and the paper clips clean and rust-free to ensure consistent magnetic attraction.

在数回形针或读取模拟表刻度时可能会产生随机误差。为了提高可靠性，每项测量重复三次并取平均值。同时，保持铁芯和回形针清洁无锈，以确保一致的磁性吸引。

12. Conclusion and Key Takeaways | 结论与要点

This investigation confirms three essential series circuit rules: (1) current is the same through all components; (2) the supply voltage equals the sum of individual p.d.s; (3) total resistance equals the sum of individual resistances. These rules hold for electromagnets as they do for any resistive loads. Furthermore, the magnetic strength of an electromagnet increases with current, illustrating the direct link between electrical and magnetic quantities in a series circuit.

本探究证实了三个基本的串联电路规律：（1）流过所有元件的电流相同；（2）电源电压等于各元件电势差之和；（3）总电阻等于各电阻之和。这些规律对电磁铁和任何电阻性负载同样成立。此外，电磁铁的磁性强弱随电流增大而增强，说明了串联电路中电学量与磁学量之间的直接联系。

By mastering series circuit measurements with electromagnets, you build a practical understanding of how current control can be used to manipulate magnetic force, a concept widely applied in electromagnetic switches, motors, and lifting devices.

通过掌握使用电磁铁进行串联电路测量，你将建立起如何利用电流控制来操纵磁力的实践理解，这一概念广泛应用于电磁开关、电动机和起重装置中。

Published by TutorHao | Physics Revision Series | aleveler.com

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