📚 Common Misconceptions in IGCSE CCEA Physics | IGCSE CCEA 物理常见误区
Many students preparing for the IGCSE CCEA Physics exam fall into predictable traps when they confuse closely related concepts or rely on everyday intuition that does not match scientific principles. Recognising and correcting these misconceptions early can dramatically improve performance in both multiple-choice questions and structured written answers. This article works through the most common misunderstandings in the CCEA specification, explains the correct physics behind each one, and shows how examiners usually test them.
很多准备 IGCSE CCEA 物理考试的学生，在混淆一些相近概念或依赖与科学原理不一致的日常直觉时，往往会掉进可预测的陷阱中。尽早识别并纠正这些误区，可以显著提高在选择题和结构化作答题中的表现。本文逐一梳理 CCEA 考纲中最常见的误解，解释每一个背后的正确物理原理，并说明考官通常怎样出题考查它们。
1. Mass and Weight | 质量与重量
in the universe. Weight, on the other hand, is the gravitational force acting on that mass. It is a vector quantity measured in newtons (N) and is calculated by Weight = mass × gravitational field strength.
质量是标量，衡量物体所含物质的多少。它的单位是千克（kg），无论你在宇宙中的任何地方都保持不变。相反，重量是作用在该质量上的重力，是矢量，单位是牛顿（N），计算公式为 重量 = 质量 × 重力场强度。
W = m g
On Earth the gravitational field strength g is approximately 10 N/kg, so a 1 kg object has a weight of about 10 N. If an astronaut travels to the Moon, the mass is unchanged but the weight is only about one-sixth of the Earth value, because the Moon's gravitational field strength is much smaller.
在地球上，重力场强度 g 约为 10 N/kg，因此 1 kg 的物体重量约为 10 N。如果宇航员前往月球，其质量不变，但重量只有地球上的约六分之一，因为月球的重力场强度小得多。
A further trap is the instrument. A beam balance compares masses and would give the same reading on the Moon, while a spring scale measures weight and would show a smaller value. Examiners often ask candidates to explain this difference in a four-mark structured question.
另一个常见陷阱在于测量仪器。天平比较的是质量，在月球上会显示相同读数；而弹簧秤测量的是重量，在月球上读数会更小。考官经常要求考生在四分结构化题目中解释这一区别。
| Feature | Mass 质量 | Weight 重量 |
| Type 类型 | Scalar 标量 | Vector 矢量 |
| Unit 单位 | kg | N |
| Instrument 仪器 | Beam balance 天平 | Spring scale 弹簧秤 |
| On the Moon 在月球上 | Unchanged 不变 | About 1/6 of Earth value 约为地球值的 1/6 |
2. Free Fall: Heavy Objects Do Not Fall Faster | 自由落体：重的物体下落并不更快
sistance, all objects fall with the same acceleration due to gravity, approximately g = 10 m/s² near the Earth's surface, regardless of their mass.
"重的物体下落更快"这一说法看似符合日常经验，但已被伽利略推翻，它是错误的。在没有空气阻力的情况下，所有物体都以相同的重力加速度下落，在地球表面附近约为 g = 10 m/s²，与其质量无关。
A feather and a hammer dropped together on the Moon, where there is no atmosphere, hit the surface at the same time. On Earth a feather falls slowly because air resistance produces an upward force that quickly balances the weight, so the resultant force becomes zero and the feather reaches a low terminal velocity. A hammer is much denser, so air resistance is negligible compared with its weight and it accelerates almost freely.
在月球上没有大气，羽毛和锤子同时下落会同时落地。在地球上羽毛下落很慢，是因为空气阻力产生一个向上的力，很快与重力平衡，合力变为零，羽毛因此达到一个很低的终端速度。锤子密度大得多，空气阻力相对于其重量可以忽略，因此几乎是自由加速下落。
r object is exactly cancelled by its greater inertia, as shown by a = W / m = m g / m = g.
请记住，自由落体加速度与质量无关，因为较重物体受到更大的重力，恰好被它更大的惯性所抵消，即 a = W / m = m g / m = g。
3. Force and Motion: Constant Velocity Needs No Force | 力与运动：匀速运动不需要力来维持
Students often think that a constant force is needed to keep an object moving at a steady speed. This is false. If an object moves at constant velocity, the resultant force on it is zero. A constant resultant force produces a constant acceleration, not a constant speed.
学生常以为要让物体保持稳定速度运动，就必须一直施加一个恒定的力。这是错的。如果物体以恒定速度运动，它受到的合力为零。恒定的合力产生的是恒定加速度，而不是恒定速度。
F = m a
In real situations a car on a straight road keeps its speed because the forward driving force is exactly balanced by friction and air resistance. Remove that driving force and the car slows down, which shows that the resultant force, not the movement itself, determines the change in motion.
在实际情境中，汽车在直路上保持速度，是因为向前的驱动力恰好被摩擦力和空气阻力平衡。一旦撤掉驱动力，车就会减速——这说明决定运动变化的是合力，而不是运动本身。
This links directly to Newton's first law and to the way CCEA examiners ask you to draw free-body diagrams and state the direction of the resultant force.
这与牛顿第一定律直接相关，也是 CCEA 考官要求你画受力图并说明合力方向时的常见考点。
4. Action and Reaction vs Balanced Forces | 作用力与反作用力 vs 平衡力
Newton's third law states that if object A exerts a force on object B, then B exerts an equal and opposite force on A. The critical point is that the two forces act on different bodies, so they never cancel each other out.
牛顿第三定律指出：如果物体 A 对物体 B 施加一个力，那么 B 也会对 A 施加一个大小相等、方向相反的力。关键点在于这两个力作用在不同的物体上，因此它们永远不会相互抵消。
Balanced forces, in contrast, are equal and opposite forces that act on the same body and therefore give a zero resultant. A book resting on a table has the normal contact force and its weight acting on the same book, so they balance. The weight of the book and the force the book exerts on the table are an action-reaction pair, because they act on two different objects.
相反，平衡力是作用在同一个物体上、大小相等方向相反的两个力，因此合力为零。一本书放在桌上，支持力和重力都作用在书上，所以它们平衡。书的重力和书对桌面的压力则是一对作用力与反作用力，因为它们分别作用在两个不同物体上。
- Same body + equal and opposite → balanced forces, resultant = 0. 同一物体 + 大小相等方向相反 → 平衡力，合力为零。
- Different bodies + equal and opposite → Newton's third law pair. 不同物体 + 大小相等方向相反 → 牛顿第三定律作用力与反作用力。
5. Inertia Does Not Depend on Speed | 惯性与速度无关
Inertia is the tendency of an object to resist a change in its motion, and it depends only on mass. A heavy lorry has more inertia than a bicycle, but a fast bicycle does not have more inertia than a slow bicycle.
惯性是物体抵抗运动状态改变的性质，它只取决于质量。重型卡车比自行车惯性大，但快速行驶的自行车并不比缓慢行驶的自行车惯性更大。
asured in kg m/s. Stopping distance grows quickly with speed because the kinetic energy to be removed rises with the square of speed.
随速度改变的是动量，定义为 p = m v，是矢量，单位是 kg m/s。刹车距离随速度迅速增加，因为需要耗散掉的动能随速度的平方增长。
Eₖ = ½ m v²
So doubling the speed quadruples the kinetic energy to be absorbed, even though the inertia has not changed at all.
因此速度加倍时，需要吸收的动能变为原来的四倍，尽管惯性完全没有改变。
6. Energy and Power: Energy Is Never Used Up | 能量和功率：能量不会被"用掉"
The principle of conservation of energy states that energy cannot be created or destroyed, only transferred from one store to another. Saying that energy is "used up" is loose language; examiners prefer "transferred to less useful stores" or "dissipated to the surroundings".
能量守恒定律指出，能量既不能创生也不能消灭，只能从一个能量库转移到另一个能量库。说能量被"用掉"是不严谨的表述；考官更希望你写"转移到不太有用的能量库"或"耗散到周围环境中"。
es (J) and power is the rate of energy transfer, measured in watts (W), where 1 W = 1 J/s.
能量与功率经常被混淆。能量的单位是焦耳（J），而功率是能量转移的速率，单位是瓦特（W），其中 1 W = 1 J/s。
P = E ÷ t
In electricity, the energy you pay for at home is measured in kilowatt-hours (kW h), which is a unit of energy, not power. A 2 kW kettle running for 0.5 hours transfers 1 kW h of energy, which costs far less than running it for a whole day.
在电学中，家庭支付的电费以千瓦时（kW h）计量，它是能量单位而不是功率单位。一台 2 kW 的电水壶工作 0.5 小时转移 1 kW h 的能量，其花费远小于让它工作一整天。
7. Current Is Not Used Up in a Circuit | 电流在电路中不会被"消耗"
A very common mistake is to say that current "gets used up" as it passes through a lamp or a resistor. It does not. Charge is conserved, so the current entering a component equals the current leaving it. In a series circuit the current is the same at every point.
一个非常常见的错误是说电流经过灯泡或电阻时被"消耗掉了"。事实并非如此。电荷守恒，因此流入元件的电流等于流出元件的电流。在串联电路中，电路中任意一点的电流都相同。
Q = I t
What the lamp does is transfer electrical energy into thermal energy and light. Energy is transferred, current is not consumed. If a student writes that "the current gets smaller after the first bulb", the examiner will deduct the mark.
灯泡做的是把电能转化为热能和光能。被转移的是能量，电流并没有被消耗。如果学生写"经过第一个灯泡后电流变小了"，考官会扣分。
In a parallel circuit the current splits between branches and rejoins, so the current from the supply equals the sum of the branch currents. That is conservation of charge expressed as a circuit rule.
在并联电路中，电流在各支路之间分流后再汇合，因此电源输出的电流等于各支路电流之和。这正是电荷守恒在电路中的表述方式。
8. Voltage, Current and Resistance | 电压、电流与电阻
Voltage is often described as "the push" that drives current, but the current that flows depends on both the voltage and the resistance of the component. A high voltage across a very large resistance may still produce a tiny current.
电压常被描述为推动电流的"推力"，但实际流过的电流取决于电压和元件电阻两者。即使电压很高，如果电阻非常大，电流也可能很小。
V = I R
Another misconception is that adding resistors in parallel increases the total resistance. It does the opposite: adding a parallel branch gives the current another path, so the total resistance falls and is always smaller than the smallest individual resistor.
另一个误解是认为并联电阻会增加总电阻。事实恰好相反：增加一条并联支路等于给电流多开了一条通路，所以总电阻下降，并且总是小于其中最小的那个电阻。
In a series circuit the current is common and the voltages add; in a parallel circuit the voltage is common and the currents add. Mixing these two rules up is one of the most expensive mistakes in the whole paper.
在串联电路中电流相同、电压相加；在并联电路中电压相同、电流相加。把这两条规律弄混，是整份试卷中代价最高的错误之一。
9. Heat and Temperature Are Not the Same | 热与温度不是一回事
Temperature measures the average kinetic energy of the particles in a substance, while heat is energy transferred from a hotter body to a colder one because of the temperature difference. A spark at 1000 °C has a very high temperature but contains very little thermal energy.
温度衡量的是物质中粒子的平均动能，而热是由于温度差而从较热物体转移到较冷物体的能量。1000 °C 的火花温度很高，但包含的热能极少。
When a substance is heated, the energy supplied may raise the temperature or change the state, but not both at once. This gives two separate equations that candidates often swap.
物质被加热时，所供给的能量可能用于升高温度，也可能用于改变状态，但不会同时进行。这对应两个不同的公式，考生常常把它们用反。
Q = m c Δθ Q = m L
During melting or boiling the temperature stays constant even though energy is still being supplied, because the energy is being used to break the bonds between particles rather than to speed them up. A common exam error is to claim the temperature rises during a change of state.
在熔化或沸腾过程中，尽管仍在持续供给能量，温度却保持不变，因为能量用于破坏粒子之间的键，而不是加快粒子运动。考试中常见错误是声称物态变化期间温度会上升。
10. Waves: Speed, Frequency and Wavelength | 波：波速、频率与波长
The wave equation relates the three quantities that describe any wave. Frequency is set by the source and does not change when a wave enters a new medium; what changes is the speed, and therefore the wavelength.
波方程把描述任何波的三个量联系起来。频率由波源决定，当波进入新介质时不会改变；改变的是波速，从而波长也随之改变。
v = f λ
A frequent mistake is to say that light slows down and therefore its frequency drops when it enters glass. In fact the frequency stays the same and the wavelength shortens, which is why the colour of the light does not change on refraction.
常见错误是认为光进入玻璃后变慢，因此频率下降。实际上频率保持不变，波长变短，这也是折射时光的颜色不会改变的原因。
- Reflection: angle of incidence = angle of reflection. 反射：入射角 = 反射角。
- Refraction towards the normal when entering a denser medium. 进入光密介质时折射光线偏向法线。
- Sound travels faster in solids than in gases because the particles are closer together. 声音在固体中比在气体中传播更快，因为粒子排列更紧密。
11. Radioactivity: Random, Unaffected by Conditions | 放射性：随机且不受外界条件影响
Radioactive decay is a random process. It is impossible to predict when a particular nucleus will decay, although the half-life tells you how long it takes for half of the nuclei in a sample to decay on average.
放射性衰变是随机过程。无法预测某一个原子核何时衰变，尽管半衰期可以告诉你样品中一半原子核平均需要多长时间衰变。
Students often believe that heating, cooling, or applying pressure can change the rate of decay. It cannot. Decay is a nuclear process, unaffected by temperature, pressure, or chemical state, which is why carbon dating works reliably.
学生常以为加热、冷却或加压会改变衰变速率。事实并非如此。衰变是核过程，不受温度、压强或化学状态影响，这也是碳定年法可靠的原因。
Half-life also does not mean that exactly half of the remaining nuclei disappear in each interval. After two half-lives, one quarter of the original nuclei remain, and after three half-lives, one eighth remains.
半衰期也不意味着每个时间间隔内恰好消失现存原子核的一半。经过两个半衰期后，剩余原有原子核的四分之一；经过三个半衰期后，剩余八分之一。
12. Exam Technique: How to Avoid These Traps | 应试技巧：如何避开这些陷阱
Most of these misconceptions cost marks in structured questions, where examiners look for specific technical vocabulary. Whenever a question mentions mass, check whether it really means weight; whenever it mentions current, check whether energy is the quantity actually being transferred.
这些误区大多会在结构化题目中造成失分，因为考官要看的是特定的专业术语。题目提到质量时，先判断它是否真的指重量；提到电流时，先判断真正被转移的量是不是能量。
- Read the command word: state, describe, explain and calculate require different depths of answer. 看清指令词：state、describe、explain、calculate 对答案深度的要求各不相同。
- Show the equation, then substitute, then give the unit. 先写公式，再代入数值，最后写单位。
- Use "resultant force", "transfer of energy" and "conservation of charge" explicitly. 明确写出 resultant force、transfer of energy、conservation of charge 等术语。
- Check whether the answer makes physical sense, for example a resistance smaller than any single resistor in parallel. 检查答案是否符合物理常理，例如并联总电阻应小于任一单个电阻。
Keeping a personal list of corrected misconceptions and reviewing it before each mock exam is one of the fastest ways to raise a CCEA Physics grade, because these errors are repeated by thousands of candidates every year.
把纠正过的误区整理成个人清单，并在每次模考前复习一遍，是提升 CCEA 物理成绩最快的途径之一，因为每年都有成千上万的考生重复同样的错误。
Published by TutorHao | IGCSE Physics Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图