📚 Year 13 AQA Physics: High-Frequency Topics and Common Pitfalls Analysis | Year 13 AQA 物理：高频考点与易错题分析
Welcome to this comprehensive revision guide covering the most commonly tested topics in Year 13 AQA Physics and frequent mistakes students make. By reviewing these high-frequency areas and their pitfalls, you can sharpen your problem‑solving skills and avoid losing marks in exams.
欢迎阅读这份全面复习指南，涵盖 Year 13 AQA 物理中最常考查的主题以及学生常犯的错误。通过复习这些高频考点及其易错点，你可以提高解题能力，避免考试失分。
1. Circular Motion | 圆周运动
Centripetal force is a resultant force, not a separate force. It must be provided by real forces such as tension, gravity, friction or the normal reaction. A common error is drawing an outward ‘centrifugal’ force on a free‑body diagram.
向心力是合力，而非一种独立的力。它必须由张力、重力、摩擦力或法向反作用力这样的真实力来提供。常见错误是在受力分析图上画出一个向外的“离心力”。
At the top of a vertical circle, the critical speed is v = √gr, where the supporting force becomes zero. Confusing this with the tension in a string at the bottom of the swing leads to frequent mistakes.
在竖直圆周的顶部，临界速度为 v = √gr，此时支撑力为零。将此与摆动最低点处的绳中张力混淆，是常见错误。
Energy conservation can be used to find speed at any point. However, many students forget that the change in gravitational potential energy depends on the vertical height difference (Δh), not on the arc length travelled.
能量守恒可用于求任意点的速度。然而许多学生忘记了重力势能的变化取决于竖直高度差 (Δh)，而非经过的弧长。
a = v²/r = r ω² F = m v²/r = m r ω²
2. Simple Harmonic Motion | 简谐运动
SHM is defined by a ∝ −x, i.e. acceleration is always directed towards the equilibrium position. Students often mislabel the direction of a and x on graphs, particularly for a pendulum bob.
简谐运动的定义是 a ∝ −x，即加速度总是指向平衡位置。学生经常在图像上误标 a 和 x 的方向，特别是在单摆摆球的情形。
extremes. A common pitfall is writing vₘₐₓ = ω/A or confusing A with twice the amplitude.
最大速度 vₘₐₓ = ωA 出现在平衡位置，最大加速度 aₘₐₓ = ω²A 出现在端点。常见易错点是写成 vₘₐₓ = ω/A，或将振幅 A 与两倍振幅混淆。
conditions. Velocity leads displacement by π/2 rad, and acceleration leads displacement by π rad. Many answers lose marks for omitting the phase constant.
位移方程 x = A cos(ωt) 或 x = A sin(ωt) 取决于初始条件。速度比位移超前 π/2 rad，加速度比位移超前 π rad。许多答案因漏写相位常数而失分。
T = 2π√m/k T = 2π√l/g Etotal = ½ m ω² A²
3. Gravitational Fields | 引力场
r² applies to point masses or outside a sphere. A common error is using the radius of the planet where r should be measured from the centre, or adding the planet’s radius incorrectly for orbiting satellites.
引力场强 g = GM/r² 适用于点质量或球体外。常见错误是当 r 应从球心量度时，错用行星半径，或对于轨道卫星误加了行星半径。
negative, and the work done to move a mass is m ΔV. Students often forget the minus sign and state that potential increases as you go further away, when in fact it becomes less negative, i.e. increases.
引力势 V = −GM/r 为负值，移动质量做功为 m ΔV。学生常忘记负号，并声称离得越远势越大，实际上它虽然数值增大但负值减小了。
For circular orbits, v = √GM/r all is using the kinetic energy formula ½mv² without realising that E is negative and half the magnitude of the potential energy.
对于圆轨道，v = √GM/r，总能量 E = −GMm/(2r)。易错点是在使用动能公式 ½mv² 时，未意识到总能量为负且其大小是势能的一半。
g = GM/r² T² ∝ r³ (Kepler’s third law)
4. Electric Fields | 电场
ply E = V/d to a radial field or confuse the direction of force on a positive test charge.
对于匀强电场，E = V/d。在点电荷周围的辐射状电场中，E = Q/(4πε₀ r²)。典型错误是对辐射场套用 E = V/d，或混淆正检验电荷的受力方向。
Electric potential energy change ΔW = qΔV; electron‑ electric fields helps, but note that mass is always positive while charge can be negative.
电势能变化 ΔW = qΔV；若学生忘记 1 eV = 1.6×10⁻¹⁹ J，电子伏特的相关计算会变得混乱。此外，引力场和电场的类比虽有帮助，但须注意质量恒为正，而电荷可为负。
Deflection of a charged particle in a uniform electric field follows projectile motion: constant acceleration perpendicular to the plates. Students often fail to split the motion into vertical and horizontal components.
带电粒子在匀强电场中的偏转遵循抛体运动：垂直于极板的恒定加速度。学生常不能将运动分解为垂直和水平分量。
E = V/d F = qE ½ m v⊥² = qV (for acceleration through a p.d.)
5. Capacitors | 电容器
itten as E = ½ QV = ½ CV² = ½ Q²/C. A common slip is writing E = CV², losing the factor ½.
电容 C = Q/V；储存的能量可写为 E = ½ QV = ½ CV² = ½ Q²/C。常见笔误是漏掉 ½，写成 E = CV²。
During charge or discharge, V = V₀ e⁻ᵗ/ᴿC, Q = Q₀ e⁻ᵗ/ᴿC. The time constant τ = RC is the time for V to fall to 37 % of its initial value. Students frequently misinterpret “half‑life” with time constant or use log₁₀ instead of natural log when linearising.
充电或放电过程中，V = V₀ e⁻ᵗ/ᴿC，Q = Q₀ e⁻ᵗ/ᴿC。时间常数 τ = RC 是电压降至初始值 37% 所需的时间。学生常将“半衰期”与时间常数混淆，或在直线化处理时使用 log₁₀ 而非自然对数。
For capacitors in series, 1/Ctotal = Σ 1/Cᵢ; in parallel, Ctotal = Σ Cᵢ. Counter‑ ries combination gives a smaller capacitance, which many students get the wrong way round.
电容器串联时，1/Ctotal = Σ 1/Cᵢ；并联时，Ctotal = Σ Cᵢ。与直觉相反，串联组合的总电容更小，许多学生会弄反。
τ = RC ln V = ln V₀ − t/(RC)
6. Magnetic Fields | 磁场
Force on a current‑ re θ is the angle between B and the current direction. The direction of force is given by Fleming’s left‑hand rule. A common slip is to apply the right‑hand rule for force on a current.
通电导线受力：F = BIL sin θ，其中 θ 是 B 与电流方向之间的夹角。力的方向由弗莱明左手定则判断。一个常见失误是用右手定则来判断电流受到的力。
/(BQ). Students often mix up mass and charge in the radius expression, or forget that the period is independent of speed.
对于在磁场中运动的带电粒子，F = BQv sin θ，且圆周运动半径 r = mv/(BQ)，周期 T = 2πm/(BQ)。学生经常在半径表达式中混淆质量与电荷，或者忘记周期与速度无关。
In the Hall effect, VH ing the sign of charge carriers; the polarity of Hall voltage reveals whether electrons or holes are the majority carriers.
在霍尔效应中，VH = BI/(nqt)。常见易错点是误判载流子的电荷符号；霍尔电压的极性可以揭示多数载流子是电子还是空穴。
F = BIL sin θ r = mv/(BQ)
7. Electromagnetic Induction | 电磁感应
A cos θ. Lenz’s law gives the direction of induced current to oppose the change in flux. Students often calculate flux change incorrectly for a coil rotating in a uniform field because they forget the cos θ term.
法拉第定律：ε = −N ΔΦ/Δt，其中 Φ = BA cos θ。楞次定律给出感应电流的方向，以阻碍磁通量的变化。学生经常在计算线圈在匀强磁场中旋转引起的磁通变化时出错，因为他们忘记了 cos θ 项。
frequency f (ω = 2πf). Many candidates incorrectly substitute f diretly into the formula.
旋转线圈的峰值电动势为 ε₀ = BANω。注意 ω 是角频率，并非线频率 f (ω = 2πf)。许多考生错误地将 f 直接代入公式。
ave energy losses due to eddy currents and flux leakage. A common exam question asks to explain why the output power is less than the input power.
理想变压器遵循 Vₛ/Vₚ = Nₛ/Nₚ 且 Pₚ = Pₛ。实际变压器由于涡流和漏磁存在能量损耗。常考题目会要求解释为什么输出功率小于输入功率。
ε = −N ΔΦ/Δt Φ = BA cos θ
8. Nuclear Physics | 核物理
frequent mistake is confusing binding energy per nucleon with total binding energy, or misreading the binding energy curve.
结合能是核子结合时释放的能量，质量亏损 Δm 对应于 E = Δm c²。常见错误是将平均结合能与总结合能混淆，或误读结合能曲线。
Radioactive decay follows N = N₀ e⁻λt and A = λN. The half‑ nits of λ (s⁻¹) or confuse the decay constant with the probability of decay per unit time.
放射性衰变遵循 N = N₀ e⁻λt 和 A = λN。半衰期 T₁/₂ = ln2 / λ。学生经常分不清 λ 的单位 (s⁻¹)，或将衰变常数与单位时间衰变概率相混淆。
Alpha, beta and gamma radiation have different ionising abilities and ranges. Alpha is highly ionising but poorly penetrating; gamma is weakly ionising but highly penetrating. In cloud chamber or detector questions, students may misidentify tracks.
α、β 和 γ 辐射的电离能力和穿透能力各不相同。α 电离强但穿透力弱；γ 电离弱但穿透力强。在云室或探测器相关问题中，学生可能会错误识别粒子径迹。
N = N₀ e⁻λt A = λN T₁/₂ = ln2 / λ
9. Thermal Physics (Ideal Gases & Thermodynamics) | 热物理（理想气体与热力学）
NkT are central. When a gas is heated at constant volume, students often forget that V is constant, so the Charles’ law relationship V ∝ T cannot be used, and p ∝ T instead.
理想气体方程 pV = nRT 和 pV = NkT 是核心。当气体在恒定体积下被加热时，学生常忘记体积不变，因此查理定律 V ∝ T 并不适用，应使用 p ∝ T。
The kinetic theory model gives pV =
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