📚 Year 10 CAIE Physics: Key Exam Topics & Error Analysis | Year 10 CAIE 物理：高频考点与易错题分析
The CAIE IGCSE Physics syllabus (0625) covers a broad range of topics, and Year 10 students often encounter challenging concepts that appear frequently in exams. This article highlights the most common topics, typical mistakes, and strategies to avoid them.
CAIE IGCSE 物理 (0625) 大纲内容广泛，Year 10 学生常会遇到考试中频繁出现的难点概念。本文聚焦最常见考点、典型错误以及避免错误的策略。
1. Motion Graphs | 运动图像分析
Students often struggle to interpret distance-time and speed-time graphs correctly. A distance-time graph’s gradient gives speed, while the area under a speed-time graph gives the distance travelled. Confusing these two is a classic error.
学生常难以正确解读距离-时间图和速度-时间图。距离-时间图的梯度表示速度，而速度-时间图下方的面积表示运动距离。混淆这两者是典型的错误。
For a curved distance-time graph, the gradient changes; to find instantaneous speed you must draw a tangent to the curve, not just pick two random points. Many candidates incorrectly take the gradient of a chord and lose marks.
对于弯曲的距离-时间图，梯度是变化的；要得出瞬时速度，必须在曲线上画出切线，而不是随便取两点。许多考生错误地取弦的梯度而失分。
Speed and velocity are often used interchangeably, but velocity is a vector. In CAIE exams, stating ‘speed’ when ‘velocity’ is required (or vice versa) can cost marks. Also remember to convert km/h to m/s by dividing by 3.6.
速度和速率常被混用，但速度是矢量。在 CAIE 考试中，当要求填 ‘velocity’ 而写成 ‘speed’（或反之）会导致扣分。还要记住将 km/h 换算成 m/s 需除以 3.6。
A negative gradient on a speed-time graph may represent deceleration, but on a distance-time graph it can indicate returning to the start. Always link the sign to the physical context.
速度-时间图中的负梯度可能代表减速，但在距离-时间图中则可能表示返回起点。始终将正负号与物理情境相联系。
2. Forces and Free-Body Diagrams | 力与受力图
Mass (kg) and weight (N) are fundamentally different, yet candidates regularly use them interchangeably. Weight is the force due to gravity: W = mg, where g ≈ 9.8 N/kg on Earth.
质量 (kg) 和重量 (N) 有本质区别，但考生经常混用。重量是由重力产生的力：W = mg，其中地球上 g ≈ 9.8 N/kg。
Drawing a free-body diagram is a high-frequency skill. Arrows must start from the centre of mass and represent all forces acting on the object. Missing the normal reaction or friction is a common omission in exam answers.
画受力图是高频技能。箭头必须从质心开始，并表示所有作用在物体上的力。遗漏法向支持力或摩擦力是考试答案中常见的疏漏。
Understanding resultant force and equilibrium tests vector addition. If forces are balanced, an object remains at constant speed or rest. Many students write ‘no forces’ when they mean ‘resultant force is zero’.
理解合力和平衡考查矢量加法。如果力平衡，物体保持匀速或静止。许多学生在意思是 ‘合力为零’ 时写成 ‘没有力’。
Terminal velocity in free fall is misunderstood. As speed increases, air resistance rises until it equals weight; then resultant force becomes zero and the object stops accelerating. The belief that ‘gravity stops acting’ is a frequent misconception.
自由落体中的终极速度常被误解。随着速度增加，空气阻力增大直至等于重力，此时合力为零，物体不再加速。认为 ‘重力停止作用’ 是常见的错误观念。
3. Energy Transfers and Efficiency | 能量转换与效率
Work done is calculated as W = F × d (force × distance moved in direction of force). The distance must be parallel to the force; using the wrong distance leads to miscalculation.
做功的计算是 W = F × d（力 × 沿力方向移动的距离）。距离必须平行于力，使用错误距离会导致计算错误。
Gravitational potential energy and kinetic energy formulas are core: GPE = mgh, KE = ½mv². A typical error is forgetting to square the velocity in KE, or mixing m (mass) and weight.
重力势能和动能公式是核心：GPE = mgh，KE = ½mv²。典型错误是忘记在动能中平方速度，或混淆质量 m 和重量。
Efficiency = (useful energy output / total energy input) × 100%. Candidates often invert the fraction or fail to express the final answer as a percentage, losing marks on straightforward calculations.
效率 = (有用能量输出 / 总能量输入) × 100%。考生常颠倒分子分母或未以百分比表示最终答案，在简单计算上失分。
Energy is conserved, but in real systems it dissipates as thermal energy. In explaining energy transfers, you must identify the store before and after. Saying ‘energy is lost’ without specifying ‘to the thermal store of the surroundings’ is incomplete.
能量守恒，但在实际系统中会以热能形式耗散。在解释能量转换时，必须标明转换前后的能量贮体。只说 ‘能量损失’ 而不指明 ‘转移到周围的热能贮体’ 是不完整的。
4. Density and Pressure | 密度与压强
Density ρ = mass / volume. Unit errors (g/cm³ vs kg/m³) are very common. Remember 1 g/cm³ = 1000 kg/m³. A student who finds a density of 1.2 kg/m³ for water has obviously misjudged scale.
密度 ρ = 质量/体积。单位错误（g/cm³ 与 kg/m³）非常普遍。记住 1 g/cm³ = 1000 kg/m³。若有学生算得水的密度是 1.2 kg/m³，显然规模判断错误。
Pressure p = F / A. When area is not in m², convert carefully. Also, liquid pressure p = ρgh relies on vertical depth h; using the slant length of a tube is a classic trap.
压强 p = F / A。当面积不是 m² 时需小心转换。此外，液体压强 p = ρgh 取决于垂直深度 h；使用试管斜边长度是经典的陷阱。
Manometers and barometers can confuse candidates. A manometer measures pressure difference, while a barometer measures atmospheric pressure. In a mercury barometer, the tube must be evacuated; any trapped air leads to a lower reading.
压力计和气压计会让考生混淆。压力计测量压强差，而气压计测量大气压强。在汞气压计中，管子必须抽真空；任何残余空气会导致读数偏低。
5. Thermal Physics: Conduction, Convection and Radiation | 热传递方式
Conduction mainly in solids through vibration and free electron movement, convection in fluids (liquid/gas) due to density changes, and radiation by infrared waves not requiring a medium. Mixing these processes is a frequent error in descriptive questions.
传导主要在固体中通过振动和自由电子移动进行，对流在流体（液体/气体）中因密度变化而发生，辐射是通过红外波不需要介质。混淆这些过程是描述题中常见的错误。
Specific heat capacity calculations use E = m c Δθ. Candidates often use mass in grams, or mistake the temperature change for the final temperature. Always check that Δθ is a difference in °C or K.
比热容计算使用 E = m c Δθ。考生经常使用克作质量单位，或将温度变化错当最终温度。务必检查 Δθ 是温度差，单位可以是 °C 或 K。
In explaining why a metal feels colder than wood at the same temperature, many students attribute it to the metal having lower temperature. The correct reason is that metal is a better conductor, so it draws energy from the hand faster – a common graph and explanation question.
在解释同温度下金属比木头感觉更冷时，许多学生归因于金属温度更低。正确原因是金属是更好的导热体，因此更快从手上吸走能量 — 这是常见的图表和解释题。
6. Waves: Reflection and Refraction | 波的反射与折射
The law of reflection states the angle of incidence equals the angle of reflection, measured from the normal, not the surface. Drawing angles incorrectly relative to the mirror surface is a frequent mistake.
反射定律指出入射角等于反射角，两者均从法线量起，而非从界面量取。相对于镜面绘制角度错误是常见错误。
Refraction occurs when a wave changes speed upon crossing a boundary. If it slows down (e.g., entering glass from air), it bends towards the normal; if it speeds up, it bends away. Many candidates reverse this rule, especially when the wave leaves the denser medium.
折射发生在波穿过边界速度改变时。如果减速（例如从空气进入玻璃），波会向法线偏折；如果加速，则偏离法线。许多考生将此规律反向，尤其是波离开较密介质时。
The wave equation v = f λ is central. Errors occur when units are mixed (e.g., frequency in kHz, wavelength in cm). Convert all to Hz and m first. Ensure you can rearrange for λ or f.
v = f × λ
波速方程 v = f λ 是核心。单位混合时（例如频率用 kHz，波长用 cm）会产生错误。首先全部转换为 Hz 和 m。务必能重新排列公式求 λ 或 f。
7. Electric Circuits: Ohm’s Law and Resistance | 电路：欧姆定律与电阻
Ohm’s law, V = IR, appears in many calculations. The most common slip is using incorrect units: V in volts, I in amps, R in ohms. Current must be in amps; using milliamps directly without conversion is a recurring error.
欧姆定律 V = IR 出现在大量计算中。最常见的疏忽是使用错误单位：电压 V 用伏特，电流 I 用安培，电阻 R 用欧姆。电流必须用安培；未转换直接使用毫安是反复出现的错误。
Resistance of a wire depends on length, cross-sectional area, and material. Longer wires have greater resistance; thicker wires have lower resistance. Students sometimes state the opposite or forget that doubling the cross-sectional area halves the resistance.
导线的电阻取决于长度、横截面积和材料。导线越长电阻越大；导线越粗电阻越小。学生有时说反，或忘记横截面积加倍电阻减半。
Interpreting I–V graphs: a straight line through origin indicates an ohmic conductor; a curve bending shows changing resistance, such as a filament lamp. Picking a point on a curve and using V/I for resistance without stating the temperature dependence misses a key explanation mark.
解读 I–V 图：过原点的直线表示欧姆导体；弯曲的曲线表示电阻变化，如灯丝灯泡。在曲线上取点用 V/I 计算电阻而不说明温度依赖性，会丢失关键解释分。
8. Series and Parallel Circuits | 串并联电路
Series circuits have the same current through all components; voltage divides. Parallel circuits have the same voltage across each branch; current splits. The most common mistake is mixing these rules, e.g., thinking current is the same in parallel.
串联电路中所有元件的电流相同，电压则分配。并联电路中各支路两端电压相同，电流则分流。最常见的错误是混淆这些规则，例如认为并联电路中电流相同。
| Property | Series | Parallel |
|---|---|---|
| Current | I = I₁ = I₂ | I = I₁ + I₂ |
| Voltage | V = V₁ + V₂ | V = V₁ = V₂ |
| Resistance | R total = R₁ + R₂ | 1/Rₜ = 1/R₁ + 1/R₂ |
In parallel resistor calculations, forgetting to take the reciprocal of the sum to find R total is a classic arithmetic slip. Many candidates stop after computing 1/R total, losing the final mark.
在并联电阻计算中，忘记对总和取倒数以得到总电阻是一个经典的算术失误。许多考生算出 1/R total 后就停止，丢失最后一步分数。
When a voltmeter must be placed in parallel and an ammeter in series, exam diagrams should show this clearly. Adding an ammeter in parallel would create a short circuit – a dangerous mistake that examiners highlight.
电压表必须并联，电流表必须串联，考试画图应明确显示。把电流表并联会造成短路 — 这是考官强调的危险错误。
9. Electromagnetic Effects | 电磁效应（发电机与电动机）
The motor effect (a current-carrying conductor in a magnetic field experiences a force) and the generator effect (moving a conductor in a magnetic field induces an e.m.f.) are often swapped in answers. The key distinction is ‘input’: electricity for motor, motion for generator.
电动机效应（载流导体在磁场中受力）和发电机效应（导体在磁场中运动产生感应电动势）常在答案中被颠倒。关键区别在于 ‘输入’：电动机输入电，发电机输入运动。
Fleming’s left-hand rule is for motor effect (force), using thumb = force, index = field, middle = current. The right-hand rule is for generators (induced e.m.f.). Using the wrong hand leads to completely reversed predictions.
弗莱明左手定则用于电动机效应（力），拇指 = 力，食指 = 磁场，中指 = 电流。右手定则用于发电机效应（感应电动势）。用错手会导致方向预测完全相反。
To increase induced e.m.f. in a generator, you can use stronger magnets, more turns in the coil, or move the magnet/coil faster. A common error is suggesting ‘increasing resistance’ – which actually reduces the induced e.m.f. in practical circuits.
要增大发电机中的感应电动势，可使用更强磁铁、增加线圈匝数或加快磁铁/线圈运动。常见错误是建议 ‘增大电阻’ — 这在实际电路中反而会减小感应电动势。
10. Radioactivity and Half-Life | 放射性与半衰期
Alpha particles (helium nuclei) are stopped by paper, beta by a few mm of aluminium, and gamma by thick lead or concrete. Many students mix up the penetrating power and ionising ability: alpha is least penetrating but most ionising, a key comparison point.
α 粒子（氦核）可被纸阻挡，β 可用几毫米铝阻挡，γ 需厚铅板或混凝土。许多学生混淆穿透能力和电离能力：α 穿透最弱但电离最强，这是关键的比较点。
Half-life is the time for half the unstable nuclei in a sample to decay. In graph interpretation, the initial count rate must be halved correctly, and repeated. A typical error is halving the time instead of the activity.
半衰期是样本中一半不稳定原子核发生衰变所需的时间。在图表解读中，初始计数率须正确减半并反复进行。典型错误是把时间减半而非计数率减半。
Background radiation must be subtracted from readings before plotting a decay curve or calculating half-life. Overlooking this creates a non-zero asymptote and an inaccurate half-life.
在画衰变曲线或计算半衰期之前，必须从读数中减去背景辐射。忽略这点会导致渐近线不为零以及半衰期不准确。
When describing safety precautions for radioactive sources, generic answers like ‘wear goggles’ gain no marks. Mention distance (long tweezers), shielding (stored in lead-lined box), and minimising exposure time.
描述放射源安全防护措施时，像 ‘戴护目镜’ 这样的泛泛之答不得分。应提及距离（长镊子）、屏蔽（存放在铅衬盒中）以及尽可能缩短接触时间。
11. Exam Technique and Common Pitfalls | 考试技巧与常见陷阱
Always include units in your final answers unless the quantity is dimensionless. Writing a number without its unit (e.g., ‘150’ instead of ‘150 N’) loses the unit mark even if the value is correct.
除非该量没有单位，一律在最终答案中包含单位。只写数字不写单位（例如写 ‘150’ 而非 ‘150 N’），即使数值正确也会丢失单位分。
Significant figures matter. CAIE papers generally expect 2 or 3 significant figures in calculations. Excessive digits (like a calculator display) suggest you haven’t thought about uncertainty and can be penalised.
有效数字很重要。CAIE 试卷通常要求计算保留 2 或 3 位有效数字。罗列过多位数（如照抄计算器显示）表明未考虑不确定度，可能被扣分。
Show your working clearly. Even if the final answer is wrong, a correct formula and substitution can earn method marks. A common lost cause is presenting just a final number with no equation.
清晰展示解题步骤。即使最终答案错误，正确的公式和代入仍能取得方法分。常见的失分原因是只写下最终数字而没有方程。
Understand command words: ‘State’ requires a brief answer, ‘Describe’ needs a step-by-step account, and ‘Explain’ demands a reason or scientific principle. Mixing describe and explain is a frequent reason for low marks on longer questions.
理解指令词：’State’ 要求简短回答，’Describe’ 需要逐步叙述，而 ‘Explain’ 则要求理由或科学原理。混淆描述和解释是长题目得分不高的常见原因。
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