IGCSE WJEC Science: Formula Summary Handbook | IGCSE WJEC 科学：公式汇总手册

📚 IGCSE WJEC Science: Formula Summary Handbook | IGCSE WJEC 科学：公式汇总手册

Welcome to your ultimate WJEC IGCSE Science formula handbook. This concise guide compiles all the essential equations you will need across Physics, Chemistry, and Biology. Each formula is presented clearly with symbol meanings and units. Keep it handy for quick revision, homework, and exam practice.

欢迎使用 WJEC IGCSE 科学公式终极手册。本指南汇集了物理、化学和生物学中所有核心公式，每个方程都配有符号说明与单位，方便你快速复习、完成作业和备战考试。

1. Motion and Forces | 运动与力

v = s / t

where v is average speed (m/s), s is distance travelled (m), and t is time taken (s).

其中 v 是平均速率 (m/s)，s 是移动距离 (m)，t 是所用时间 (s)。

a = (v − u) / t

where a is acceleration (m/s²), v is final velocity (m/s), u is initial velocity (m/s), and t is time (s).

其中 a 是加速度 (m/s²)，v 是末速度 (m/s)，u 是初速度 (m/s)，t 是时间 (s)。

v² = u² + 2as

Uniform acceleration equation linking velocities, acceleration, and displacement s (m).

匀加速运动方程，联系速度、加速度与位移 s (m)。

s = ut + ½at²

Displacement s (m) after time t under uniform acceleration a. The term ½ is one-half.

匀加速运动中经过时间 t 的位移 s (m)，½ 表示二分之一。

F = ma

Newton’s second law: resultant force F (N) equals mass m (kg) times acceleration a (m/s²).

牛顿第二定律：合力 F (N) 等于质量 m (kg) 乘以加速度 a (m/s²)。

W = mg

Weight W (N) is mass m (kg) × gravitational field strength g (on Earth approx. 9.8 N/kg or 10 N/kg).

重力 W (N) 等于质量 m (kg) × 重力场强度 g (地球约 9.8 N/kg 或 10 N/kg)。

p = mv

Momentum p (kg m/s) is mass m (kg) × velocity v (m/s). Momentum is a vector.

动量 p (kg m/s) 等于质量 m (kg) × 速度 v (m/s)。动量为矢量。

impulse = Ft = Δp = mv − mu

Impulse (N s) is the product of force and time, and equals the change in momentum.

冲量 (N s) 是力与时间的乘积，等于动量的变化量。

F = kx

Hooke’s law: force F (N) equals spring constant k (N/m) times extension x (m), within the elastic limit.

胡克定律：在弹性限度内，力 F (N) 等于弹簧常数 k (N/m) 乘以伸长量 x (m)。

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2. Energy, Work, and Power | 能量、功与功率

W = Fd

Work done W (J) when a constant force F (N) moves an object a distance d (m) in the direction of the force.

恒力 F (N) 使物体沿力的方向移动距离 d (m) 所做的功 W (J)。

ΔEₚ = mgΔh

Change in gravitational potential energy ΔEₚ (J) = mass m (kg) × g × change in height Δh (m).

重力势能变化量 ΔEₚ (J) = 质量 m (kg) × g × 高度变化 Δh (m)。

Eₖ = ½mv²

Kinetic energy Eₖ (J) is half the mass m (kg) times the square of the speed v (m/s).

动能 Eₖ (J) 等于质量 m (kg) 乘以速率 v (m/s) 平方的一半。

P = W / t = E / t

Power P (W) is the rate of doing work or transferring energy: work or energy (J) divided by time t (s).

功率 P (W) 是做功或能量转移的速率：功或能量 (J) 除以时间 t (s)。

P = Fv

For an object moving at constant velocity v (m/s) against a constant force F (N), power P = Fv.

物体以恒定速度 v (m/s) 克服恒力 F (N) 时，功率 P = Fv。

efficiency = (useful output / total input) × 100%

Efficiency measures how well energy is converted; express as a percentage.

效率衡量能量转换的有效程度，以百分比表示。

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3. Electricity and Circuits | 电学与电路

Q = It

Charge Q (C) = current I (A) × time t (s).

电荷量 Q (C) = 电流 I (A) × 时间 t (s)。

V = IR

Ohm’s law: potential difference V (V) = current I (A) × resistance R (Ω).

欧姆定律：电势差 V (V) = 电流 I (A) × 电阻 R (Ω)。

P = IV = I²R = V² / R

Electrical power P (W) can be calculated using any of these three equivalent forms.

电功率 P (W) 可由这三个等价公式中的任何一个计算。

E = Pt = VIt

Energy transferred E (J) = power P (W) × time t (s), or E = VIt for an electrical component.

转移的能量 E (J) = 功率 P (W) × 时间 t (s)，或用电器 E = VIt。

Rₜ = R₁ + R₂ + …

Total resistance for resistors connected in series.

串联电阻总电阻。

1 / Rₜ = 1 / R₁ + 1 / R₂ + …

Total resistance for resistors connected in parallel (for two resistors, Rₜ = (R₁R₂) / (R₁+R₂)).

并联电阻总电阻的倒数等于各电阻倒数之和（仅两个电阻时 Rₜ = (R₁R₂)/(R₁+R₂)）。

Vₚ / Vₛ = Nₚ / Nₛ

Ideal transformer: primary voltage Vₚ, secondary voltage Vₛ, turns ratio Nₚ/Nₛ.

理想变压器：原边电压 Vₚ，副边电压 Vₛ，匝数比 Nₚ/Nₛ。

Vₚ Iₚ = Vₛ Iₛ

For a 100% efficient transformer, input power equals output

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