📚 IGCSE WJEC Physics: Formula Summary Handbook | IGCSE WJEC 物理：公式汇总手册
This comprehensive handbook gathers all essential formulas required for the IGCSE WJEC Physics specification. Each equation is presented in a clear, bilingual format, with worked examples where helpful. Use this resource to reinforce your understanding and commit key relationships to memory before the exam.
这本全面的手册汇总了 IGCSE WJEC 物理考试所需的所有核心公式。每个方程均以清晰的双语形式呈现，并在适当处配有示例。利用这份资料巩固理解，并在考试前牢牢记住关键关系。
1. Kinematics | 运动学
Average speed is the total distance travelled divided by the total time taken. This formula applies when speed is not necessarily constant.
平均速率等于通过的总距离除以总时间。当速率不一定恒定时使用此公式。
average speed = total distance / total time → v = d / t
The acceleration of an object is the rate at which its velocity changes. It can be calculated from the change in velocity over the time interval.
物体的加速度是速度变化的快慢程度，可用速度变化量除以时间间隔计算。
acceleration = change in velocity / time → a = (v - u) / t
For uniform acceleration, the final speed, initial speed, acceleration and distance are related by a motion equation that does not involve time.
对于匀加速运动，末速度、初速度、加速度和位移之间的关系可用一个不含时间的运动方程表示。
v² = u² + 2 a s
2. Force, Mass and Acceleration | 力、质量与加速度
A resultant force causes a mass to accelerate. The acceleration is directly proportional to the force and inversely proportional to the mass.
合力使物体产生加速度。加速度与合力成正比，与质量成反比。
F = m a
Weight is the gravitational force acting on a mass, equal to the product of mass and gravitational field strength.
重量是作用在质量上的引力，等于质量与引力场强度的乘积。
W = m g
3. Turning Forces and Equilibrium | 力矩与平衡
The moment of a force about a pivot is the product of the force and the perpendicular distance from the pivot to the line of action of the force.
力对支点的力矩等于力与支点到力作用线的垂直距离的乘积。
moment = force × perpendicular distance → M = F d
For an object in equilibrium, the sum of clockwise moments about any pivot equals the sum of anticlockwise moments.
物体处于平衡状态时，关于任意支点的顺时针力矩之和等于逆时针力矩之和。
Σ clockwise moments = Σ anticlockwise moments
4. Energy and Work | 能量与功
Work is done when a force moves an object. The amount of work is the product of the force and the distance moved in the direction of the force.
力使物体移动时做功，功的大小等于力与在力的方向上移动的距离的乘积。
W = F s
Kinetic energy depends on mass and the square of speed. It is one of the most commonly tested energy formulas.
动能取决于质量和速度的平方，这是最常考查的能量公式之一。
Eₖ = ½ m v²
Gravitational potential energy gained by an object raised above the ground depends on its mass, height and gravitational field strength.
物体升高时所增加的引力势能取决于质量、高度和引力场强度。
Eₚ = m g h
5. Power and Efficiency | 功率与效率
Power is the rate at which work is done or energy is transferred. It can be calculated from work done or energy change divided by time.
功率表示做功或能量转移的快慢，可用做功量或能量变化除以时间进行计算。
P = W / t
Efficiency expresses how much of the total input energy is converted into useful output energy. It is often given as a percentage.
效率表示总输入能量中有多少转化为有用的输出能量，通常以百分比表示。
efficiency = useful output energy / total input energy × 100%
6. Density and Pressure | 密度与压强
Density links mass and volume, describing how much mass is packed into a given space.
密度联系质量与体积，描述单位空间内含有多少质量。
ρ = m / V
Pressure on a surface is defined as the force acting per unit area. A larger area reduces the pressure for the same force.
作用在表面上的压强定义为单位面积上的力。在力相同的情况下，面积越大压强越小。
p = F / A
Pressure at a depth in a fluid depends on the density of the fluid, gravitational field strength and the height of the fluid column.
液体中某一深度的压强取决于液体密度、引力场强度和液柱高度。
p = h ρ g
7. Waves | 波
The wave speed is the product of frequency and wavelength. This equation applies to all types of waves, including light and sound.
波速等于频率与波长的乘积。该方程适用于包括光和声在内的所有类型的波。
v = f λ
Frequency is the number of complete waves per second; it is the reciprocal of the period.
频率是每秒完整波的个数，等于周期的倒数。
f = 1 / T
8. Electricity Basics | 电学基础
Electric current is the rate of flow of charge. A current of one ampere is a flow of one coulomb of charge per second.
电流是电荷流动的速率。1安培的电流相当于每秒流过1库仑的电荷。
I = Q / t
Voltage (potential difference) is the energy transferred per unit charge. One volt is one joule per coulomb.
电压（电势差）是单位电荷转移的能量。1伏特等于每库仑1焦耳。
V = E / Q
Resistance measures how difficult it is for current to flow. It is the ratio of voltage to current.
电阻衡量电流流动的难易程度，是电压与电流的比值。
R = V / I
9. Resistance and Electrical Power | 电阻与电功率
For a given material, resistance depends on its resistivity, length and cross-sectional area. Doubling the length doubles the resistance.
对于给定材料，电阻取决于电阻率、长度和横截面积。长度加倍，电阻加倍。
R = ρ L / A
Electrical power is the rate at which electrical energy is transferred. Three equivalent forms are used depending on which quantities are known.
电功率是电能转移的速率。根据已知量不同，有三个等效形式可用。
P = I V P = I² R P = V² / R
In series circuits, current is the same everywhere and the total resistance is the sum of individual resistances. In parallel, the voltage across each branch is the same.
串联电路中各处电流相等，总电阻等于各电阻之和。并联电路中各支路两端电压相同。
Series: Rₜ = R₁ + R₂ + ... Parallel: 1/Rₜ = 1/R₁ + 1/R₂ + ...
10. Transformers | 变压器
An ideal transformer relates the primary and secondary voltages to the number of turns on each coil. There is no energy loss in the process.
理想变压器将初级和次级电压与各自线圈的匝数联系起来，过程中无能量损耗。
Vₚ / Vₛ = Nₚ / Nₛ
For 100% efficient transformers, electrical power input equals output, so the product of voltage and current is the same for both coils.
对于效率100%的变压器，输入电功率等于输出电功率，因此两线圈的电压与电流乘积相等。
Vₚ Iₚ = Vₛ Iₛ
11. Thermal Physics | 热学
When an object is heated without a change of state, its temperature rise depends on the energy supplied, its mass and specific heat capacity.
物体在无状态变化时被加热，其温升取决于提供的能量、质量以及比热容。
Q = m c Δθ
For a fixed mass of gas at constant temperature, pressure and volume are inversely proportional (Boyle's law).
对于恒定温度下的一定质量气体，压强与体积成反比（玻意耳定律）。
p₁ V₁ = p₂ V₂
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