📚 A-Level WJEC Physics: Formula Summary Handbook | A-Level WJEC 物理：公式汇总手册
Welcome to the ultimate formula summary handbook for WJEC A-Level Physics. This collection compiles all essential equations, their meanings, and contexts – from mechanics to quantum physics. Mastering these formulas is key to solving problems and understanding physical principles.
欢迎使用 WJEC A-Level 物理公式汇总手册。本手册汇集了从力学到量子物理的所有核心公式、含义和应用场景。掌握这些公式是解题和理解物理原理的关键。
1. Kinematics (SUVAT) | 运动学（SUVAT）
The four SUVAT equations describe uniformly accelerated motion in a straight line. They link displacement (s), initial velocity (u), final velocity (v), acceleration (a), and time (t).
四个 SUVAT 方程描述沿直线的匀加速运动，联系位移 (s)、初速度 (u)、末速度 (v)、加速度 (a) 和时间 (t)。
Equation without displacement: final velocity is initial velocity plus acceleration times time.
不含位移的方程：末速度等于初速度加加速度乘时间。
v = u + at
Equation without final velocity: displacement relates initial velocity, time and acceleration.
不含末速度的方程：位移与初速度、时间和加速度相关。
s = ut + ½ at²
Equation without acceleration: displacement is the average velocity multiplied by time.
不含加速度的方程：位移等于平均速度乘时间。
s = ½ (u + v) t
Equation without time: final velocity squared is initial velocity squared plus twice the product of acceleration and displacement.
不含时间的方程：末速度的平方等于初速度的平方加两倍加速度与位移的乘积。
v² = u² + 2as
2. Newton’s Laws & Momentum | 牛顿定律与动量
Newton’s second law states that the net force acting on an object equals its mass multiplied by acceleration.
牛顿第二定律指出，物体所受合外力等于质量与加速度的乘积。
F = ma
Momentum is defined as the product of mass and velocity.
动量定义为质量与速度的乘积。
p = mv
Impulse equals the change in momentum and is given by the product of force and time.
冲量等于动量的变化，由力乘时间得出。
FΔt = Δp
In a closed system, total momentum before a collision equals total momentum after, provided no external forces act.
在封闭系统中，若无外力作用，碰撞前的总动量等于碰撞后的总动量。
m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂
3. Work, Energy & Power | 功、能与功率
Work done by a constant force is the product of force, displacement, and the cosine of the angle between them.
恒力做功等于力、位移及二者夹角余弦的乘积。
W = Fd cosθ
Kinetic energy depends on mass and the square of speed.
动能取决于质量和速度的平方。
KE = ½ mv²
Gravitational potential energy near Earth’s surface is mass times gravitational field strength times height.
地表的重力势能等于质量乘以重力场强度乘以高度。
GPE = mgh
Power is the rate of doing work, also expressed as force times velocity.
功率是做功的速率，也可表示为力乘速度。
P = W / t = Fv
Efficiency is the ratio of useful output power to total input power.
效率为有用输出功率与总输入功率之比。
Efficiency = (useful power out) / (total power in)
4. Circular Motion | 圆周运动
Angular velocity is the rate of change of angle, related to period or frequency.
角速度是角度的变化率，与周期或频率有关。
ω = Δθ / Δt = 2π / T = 2πf
Linear speed and angular speed are linked by the radius.
线速度与角速度通过半径联系。
v = ωr
Centripetal acceleration points to the centre and can be expressed in terms of speed or angular speed.
向心加速度指向圆心，可用速度或角速度表示。
a = v² / r = ω² r
Centripetal force is mass times centripetal acceleration.
向心力等于质量乘以向心加速度。
F = mv² / r = mω² r
5. Waves | 波
Wave speed equals frequency multiplied by wavelength.
波速等于频率乘波长。
v = fλ
Refractive index relates the speed of light in a vacuum to its speed in a medium.
折射率是真空光速与介质光速的比值。
n = c / v
Snell’s law describes refraction at a boundary between two media.
斯涅耳定律描述光在两种介质界面的折射。
n₁ sinθ₁ = n₂ sinθ₂
For a double-slit experiment, fringe spacing depends on wavelength, slit-to-screen distance and slit separation.
双缝干涉中，条纹间距与波长、缝到屏距离及缝间距有关。
Δx = λD / d
Diffraction grating maxima satisfy d sinθ = nλ, where n is the order number.
衍射光栅亮纹条件为 d sinθ = nλ，n 为级数。
d sinθ = nλ
6. Electric Fields & Circuits | 电场与电路
Electric field strength is force per unit charge, also expressed as potential gradient for uniform fields.
电场强度是单位电荷所受的力，匀强电场中也等于电势梯度。
E = F / q = V / d
Ohm’s law relates potential difference, current, and resistance.
欧姆定律联系电势差、电流和电阻。
V = IR
Resistance of a wire depends on resistivity, length, and cross-sectional area.
导线的电阻由电阻率、长度和横截面积决定。
R = ρL / A
Electrical power can be written in three useful forms.
电功率有三种常用表达式。
P = IV = I²R = V² / R
Kirchhoff’s current law: total current entering a junction equals total current leaving.
基尔霍夫电流定律：流入节点的电流之和等于流出电流之和。
ΣI_in = ΣI_out
Kirchhoff’s voltage law: the sum of e.m.f.s around any closed loop equals the sum of p.d.s.
基尔霍夫电压定律：闭合回路中电动势之和等于各元件电压降之和。
Σε = ΣIR
7. Capacitors | 电容器
Capacitance is charge stored per unit potential difference.
电容为单位电势差所存储的电荷量。
C = Q / V
Energy stored in a capacitor can be expressed in three equivalent ways.
电容器储存的能量有三种等价表达式。
E = ½ QV = ½ CV² = Q² / (2C)
For capacitors in parallel, the total capacitance is the sum of individual capacitances.
并联时，总电容等于各电容之和。
C_total = C₁ + C₂ + …
For capacitors in series, the reciprocal of total capacitance is the sum of reciprocals.
串联时，总电容的倒数等于各电容倒数之和。
1 / C_total = 1 / C₁ + 1 / C₂ + …
The time constant τ = RC determines the rate of charging or discharging.
时间常数 τ = RC 决定充放电的速率。
τ = RC
During discharge, charge decays exponentially: Q = Q₀ e^(-t / RC).
放电时电荷指数衰减：Q = Q₀ e^(-t / RC)。
Q = Q₀ e^(-t / RC)
8. Magnetic Fields & Electromagnetic Induction | 磁场与电磁感应
The force on a current-carrying conductor in a magnetic field is F = BIl sinθ, where θ is the angle between current and field.
通电导体在磁场中所受力为 F = BIl sinθ，θ 为电流与磁场方向的夹角。
F = BIl sinθ
Magnetic flux is the product of magnetic flux density and area, for a field perpendicular to the area.
当磁场垂直于面积时，磁通量等于磁通密度与面积的乘积。
Φ = BA
Faraday’s law states that the induced e.m.f. is proportional to the rate of change of flux linkage.
法拉第定律指出，感应电动势与磁链变化率成正比。
ε = -N ΔΦ / Δt
For an ideal transformer, the voltage ratio equals the turns ratio.
理想变压器中，电压比等于匝数比。
V_s / V_p = N_s / N_p
Assuming 100% efficiency, input power equals output power for a transformer.
假设效率100%，变压器输入功率等于输出功率。
I_p V_p = I_s V_s
9. Thermal Physics | 热物理
Heat energy required to change temperature depends on mass, specific heat capacity, and temperature change.
改变温度所需的热量与质量、比热容和温度变化成正比。
Q = mcΔθ
Heat energy for a change of state (latent heat) is mass times specific latent heat.
物态变化所需的热量（潜热）等于质量乘比潜热。
Q = mL
The ideal gas law links pressure, volume, temperature, and amount of substance.
理想气体定律联系压强、体积、温度和物质的量。
pV = nRT
In terms of the number of molecules, pV = NkT, where k is Boltzmann’s constant.
用分子数表达时为 pV = NkT，k 为玻尔兹曼常量。
pV = NkT
The average kinetic energy of a gas molecule is directly proportional to absolute temperature.
气体分子的平均动能与绝对温度成正比。
KE_avg = (3/2) kT
10. Quantum Physics & Atoms | 量子物理与原子
Photon energy is the product of Planck’s constant and frequency.
光子能量为普朗克常数与频率的乘积。
E = hf
Photoelectric effect: photon energy equals work function plus maximum kinetic energy of emitted electrons.
光电效应：光子能量等于逸出功加出射电子的最大动能。
hf = φ + KE_max
Energy levels in atoms produce photons when electrons transition: hf = E₂ – E₁.
原子中电子跃迁时发射光子：hf = E₂ – E₁。
hf = E₂ – E₁
The de Broglie wavelength of a particle relates to its momentum.
粒子的德布罗意波长与动量有关。
λ = h
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