题型概述：电学与磁学Question types: electricity and magnetism
IPC 电磁学题常以电路、家用电器和磁化现象为背景。Section A 选择题每题 1 分；本页 B12 为 5 分，C14 为 15 分，重在写清原理与推导。常见失分点是把电压与功率的关系当作线性、误读电压表跨接的位置，以及混淆电池内外的热量。IPC electricity questions use circuits, appliances and magnetisation. Section A questions carry 1 mark each; B12 here carries 5 and C14 carries 15, rewarding explanation and working. Common losses come from treating power as linear in voltage, misreading meter connections, and confusing internal with external heating.
1电功率与能量Electrical power and energy
先确认哪个量保持不变。固定电阻时，电压平方决定功率；相同加热任务所需能量近似相同。First identify what is held constant. At fixed resistance, voltage squared sets the power; the same heating task requires approximately the same energy.
电压加倍并非功率加倍。Doubling voltage does not merely double power.
2回路电压与电压表Loop voltage and voltmeters
沿回路的电压升高与降低相抵。电压表应并联；误串联时，大内阻几乎分走全部电压。Voltage rises and drops balance around a loop. A voltmeter belongs in parallel; in series its high resistance takes almost the entire voltage.
充电时电源电动势与电池电动势相减。During charging the supply and battery emfs oppose.
3磁化与能量去向Magnetisation and energy destinations
软铁受磁场作用会暂时磁化；同向并排磁化产生横向排斥。电池题则要区分化学储能和电阻发热。Soft iron is temporarily magnetised by a field; parallel side-by-side magnetisation produces transverse repulsion. In battery problems, distinguish chemical storage from resistive heat.
磁极方向看磁场；温度变化看电池内部发热。The field sets pole directions; internal heating sets battery temperature.
一分钟练习：保持 R = 10 ΩOne-minute check: keep R = 10 Ω
| 子题型Subtype | 识别特征Clue | 核心步骤Key step | 真题Question |
|---|---|---|---|
| 电功率曲线Power–voltage graph | 固定电阻Fixed resistor | P ∝ V²P ∝ V² | 2025 A4 |
| 电热水壶的供电电压Kettle supply voltage | 换电源电压New supply voltage | t ∝ 1/V²t ∝ 1/V² | 2023 A5 |
| 并排铁棒的磁化Magnetising parallel rods | 软铁与线圈Soft iron and coil | 同侧同极Matching poles | 2022 A6 |
| 误串联的电压表A voltmeter in series | 电压表串联Meter in series | 读清 6 V 电源Read the 6 V supply | 2023 B12 |
| 充电、效率与温升Charging, efficiency and heating | 温度上限Temperature limit | 先电路，后热量Circuit, then heat | 2024 C14 |