题型概述：原子核与实验技能Question types: atomic, nuclear & practical skills
本组从 IPC 2023–2025 年题目中选出三道 1 分选择题和两道 5 分实验解释题，共 13 分。核物理常把“每次”“每秒”“减半次数”混在一起；实验题则要求沿着公式追踪误差，并用物理因果链解释观察。B 题在题库按力学或电磁学归类，本页按实验操作与结果解释的技能选入。This set contains three one-mark multiple-choice questions and two five-mark experimental explanations from IPC 2023–2025, totalling 13 marks. Nuclear questions distinguish energy per event, events per second and numbers of halvings. Practical questions trace measurement errors through equations and explain observations using physical causes. The B questions are indexed under mechanics or electricity in the bank and included here for their experimental skills.
页面积分用于练习进度。B 题的自动检查只覆盖数值或明确标注的补充自检；原卷 5 分仍取决于完整文字解释。先答题再看解答；提示会减少本页练习分。Page credit tracks practice progress. Automatic B-question checks cover only numbers or clearly labelled added checks; the original five marks still require full written explanations. Answer before opening solutions; hints reduce page credit.
1衰变：每次减半，不是每次减同一个数Decay: halve repeatedly, rather than subtract a fixed amount
活度 A 是每秒发生的衰变次数。半衰期 T½ 后，活度和未衰变核数都减为原来的一半；不同样品的起始活度可以不同，但同一核素的半衰期相同。Activity A is the decay rate. After a half-life T½, both activity and the number of undecayed nuclei halve. Samples may have different initial activities, but the same isotope has the same half-life.
把时间先写成“几个半衰期”，计算最清楚。Express time as a number of half-lives before calculating.
2从单次能量到功率From energy per decay to power
功率是每秒的能量。若给出每克活度，先求每克的放热功率，再由所需总功率求质量；只有题目给出转换效率时才加入效率因子。Power is energy per second. If activity per gram is given, calculate the released power per gram first and then infer mass from the required power. Include a conversion efficiency only when the question supplies one.
量纲检查：s⁻¹ × J = W；若 aₛ 按每克给出，m 就用克。Units: s⁻¹ × J = W; if aₛ is per gram, use grams for m.
3实验：先看公式，再比较影响的比例Experiments: use the formula and compare relative effects
系统性的长度偏差会通过速度公式传到加速度。仪器接错会改变电路本身；落球实验则要控制高度和初速度，并比较阻力与重力的比例。解释题需写出“原因 → 物理量变化 → 观察结果”。A systematic length bias propagates through velocity into acceleration. Incorrect instrument wiring changes the circuit itself. Falling-ball comparisons require controlled height and initial velocity and comparison of drag with weight. Write explanations as cause → change in a physical quantity → observation.
重复测量不能消除固定的标定偏差，也不能修复错误接线。Repeating measurements does not remove a fixed calibration bias or correct wrong wiring.
| 子题型Sub-type | 识别特征Recognition | 核心步骤Core step | 真题Question |
|---|---|---|---|
| 半衰期Half-life | 活度曲线Activity curve | 数减半次数Count halvings | 2025 A10 |
| 核能功率Nuclear power | Bq 与 JBq and J | 先求 W/gFind W/g | 2023 A9 |
| 误差传播Error propagation | 长度测大Length too large | 沿公式追踪偏差Trace the bias | 2025 A7 |
| 仪器接线Instrument wiring | 电压表串联Meter in series | 比较电阻和分压Compare resistance and voltage division | 2023 B12 |
| 控制变量实验Controlled experiment | 同高释放不同球Different balls, same height | 比较 F阻/mCompare drag/m | 2024 B12 |