📚 Pre-U WJEC Physics: Vocabulary & Terminology Quick Study Guide | Pre-U WJEC 物理：词汇术语速记指南
Mastering physics terminology is essential for success in the Pre-U WJEC Physics examination. This guide provides concise definitions of key terms across all major topics, helping you build a solid vocabulary foundation for problem‑solving and extended responses.
掌握物理术语是 Pre‑U WJEC 物理考试成功的关键。本指南提供所有主要主题中关键术语的简明定义，帮助您建立扎实的词汇基础，以应对问题解决和长篇答题。
1. Physical Quantities & Units | 物理量与单位
Scalar: a physical quantity described solely by its magnitude. Examples include mass, time, temperature and speed.
标量：仅由大小描述的物理量，例如质量、时间、温度和速率。
Vector: a quantity that possesses both magnitude and direction. Displacement, velocity, force and momentum are vectors, often represented by arrows where length indicates magnitude and orientation gives direction.
矢量：既有大小又有方向的量。位移、速度、力和动量是矢量，常用箭头表示，其长度表示大小，方向指示朝向。
Displacement: the change in position of an object in a specific direction, measured as the straight‑line distance from the initial to the final point. It is a vector, symbol s or x, unit metre (m).
位移：物体在特定方向上位置的变化，测量从起点到终点的直线距离，是矢量，符号为 s 或 x，单位为米 (m)。
Velocity: rate of change of displacement; a vector quantity. Average velocity is calculated as total displacement divided by time taken, v = Δs/Δt. Instantaneous velocity is the gradient of a displacement–time graph.
速度：位移随时间的变化率，是矢量。平均速度等于总位移除以所用时间，v = Δs/Δt。瞬时速度是位移‑时间图线的斜率。
Acceleration: rate of change of velocity; a vector. It is given by a = Δv/Δt. Negative acceleration (deceleration) occurs when velocity magnitude decreases. The SI unit is m s⁻².
加速度：速度随时间的变化率，是矢量，公式为 a = Δv/Δt。当速度大小减小时出现负加速度（减速）。SI 单位为 m s⁻²。
2. Kinematics & Graphs | 运动学与图线
Displacement–time graph: a plot showing how displacement changes with time. The gradient gives velocity; a straight line indicates constant velocity, and a curve indicates changing velocity.
位移‑时间图：显示位移随时间变化的图线。斜率给出速度；直线表示匀速，曲线表示变速。
Velocity–time graph: a graph of velocity against time. Its gradient yields acceleration, and the area under the graph represents displacement.
速度‑时间图：速度随时间变化的图线。其斜率给出加速度，图线下面积代表位移。
SUVAT equations v)t. Here u is initial velocity, v final velocity, a acceleration, t time, s displacement.
匀变速直线运动方程 (SUVAT)：适用于匀加速直线运动的运动学方程组：v = u + at, s = ut + ½at², v² = u² + 2as, s = ½(u+v)t。其中 u 为初速度，v 为末速度，a 为加速度，t 为时间，s 为位移。
Acceleration of free fall (g): the acceleration experienced by an object under the sole influence of a gravitational field near the Earth's surface. Its standard value is 9.81 m s⁻², directed downwards.
自由落体加速度 (g)：物体仅在地球表面附近重力场作用下获得的加速度，标准值为 9.81 m s⁻²，方向向下。
Projectile motion: two‑dimensional motion under constant gravitational acceleration. The horizontal component of velocity remains constant (neglecting air resistance), while the vertical component changes linearly due to g. The path is a parabola.
抛体运动：在恒定重力加速度下的二维运动。水平分速度保持不变（忽略空气阻力），垂直分速度因 g 线性变化。轨迹为抛物线。
3. Forces & Dynamics | 力与动力学
Newton's first law: an object remains at rest or in uniform motion in a straight line unless acted upon by a resultant external force. This is the principle of inertia.
牛顿第一定律：物体将保持静止或匀速直线运动状态，除非受到合外力的作用。这是惯性原理。
Newton's second law: the rate of change of momentum of an object is proportional to the resultant force and takes place in the direction of that force. Commonly written as F = ma for constant mass.
牛顿第二定律：物体的动量变化率与合外力成正比，并沿力的方向发生。对于恒定质量，常用形式为 F = ma。
Momentum: the product of an object's mass and velocity, p = mv. Momentum is a vector quantity that is conserved in a closed system with no external forces. The SI unit is kg m s⁻¹.
动量：物体质量与速度的乘积，p = mv。动量是矢量，在没有外力的封闭系统中守恒。SI 单位为 kg m s⁻¹。
Impulse the time for which it acts: Impulse = FΔt = Δp. It can be found as the area under a force–time graph.
冲量：物体动量的变化，等于合外力与作用时间的乘积：冲量 = FΔt = Δp，可通过力‑时间图线下面积求得。
Conservation of momentum: in a closed system free from external resultant forces, the total momentum before an interaction equals the total momentum after the interaction.
动量守恒：在没有合外力的封闭系统中，相互作用前的总动量等于相互作用后的总动量。
Centripetal force ssary for circular motion. Its magnitude is F = mv²/r = mrω², where ω is angular velocity.
向心力：指向圆周路径中心的合外力，是维持圆周运动所必需的。其大小为 F = mv²/r = mrω²，其中 ω 为角速度。
4. Work, Energy & Power | 功、能与功率
Work done the displacement itself: W = Fd cosθ. Work transfers energy; the SI unit is the joule (J).
功：力在位移方向上的分量与位移的乘积：W = Fd cosθ。做功传递能量；SI 单位是焦耳 (J)。
Kinetic energy: energy due to motion, given by Ek = ½mv². The work–gy theorem states that the net work done on an object equals its change in kinetic energy.
动能：由于运动而具有的能量，表达式为 Ek = ½mv²。动能定理指出，对物体做的总功等于其动能的变化。
Gravitational potential energy: energy stored in an object by virtue of its height in a gravitational field: ΔEp = mgΔh (near Earth's surface).
重力势能：物体在重力场中由于位置高度而存储的能量：ΔEp = mgΔh（近地表适用）。
Elastic potential energy: energy stored in a deformed elastic object. For a spring obeying Hooke's law, it is given by E = ½kx², where k is the spring constant and x the extension.
弹性势能：发生弹性形变的物体储存的能量。对遵守胡克定律的弹簧，E = ½kx²，其中 k 为劲度系数，x 为伸长量。
Power rring energy. Average power P = W/t or ΔE/Δt. The SI unit is the watt (W), equivalent to J s⁻¹.
功率：做功或能量转换的速率。平均功率 P = W/t 或 ΔE/Δt。SI 单位是瓦特 (W)，即 J s⁻¹。
Efficiency power), often expressed as a percentage. Efficiency = (useful output / total input) × 100%. It is always less than 100% due to dissipative losses.
效率：有用输出能量（或功率）与总输入能量（或功率）之比，常用百分数表示。效率 = (有用输出 / 总输入) × 100%。由于耗散损失，效率始终低于 100%。
5. Materials | 材料
Hooke's law force, provided the elastic limit is not exceeded: F = kx, where k is the spring constant.
胡克定律：在弹性限度内，弹性物体的伸长量与施加的力成正比：F = kx，其中 k 为劲度系数。
Stress: the force per unit cross‑ional area applied to a material: σ = F/A. The SI unit is the pascal (Pa), equivalent to N m⁻².
应力：施加在材料单位截面积上的力：σ = F/A。SI 单位为帕斯卡 (Pa)，即 N m⁻²。
Strain is the original length. Strain is dimensionless, often expressed as a ratio or percentage.
应变：材料的相对伸长量：ε = ΔL/L₀，其中 L₀ 为原长。应变是无量纲量，常用比值或百分数表示。
Young modulus ile stress to tensile strain in the linear region: E = σ/ε. Its unit is Pa. A steep stress–strain graph indicates a high Young modulus.
杨氏模量：衡量材料刚度的量，定义为拉伸应力与拉伸应变在线性区的比值：E = σ/ε。单位为 Pa。应力‑应变图陡峭表示杨氏模量高。
Elastic limit: the maximum stress a material can withstand and still return to its original dimensions when the load is removed. Beyond this point, plastic deformation occurs.
弹性极限：材料能承受且卸载后可恢复原尺寸的最大应力。超过此点将发生塑性形变。
Ductile & Brittle: a ductile material (e.g., copper) undergoes significant plastic deformation before fracture and displays necking; a brittle material (e.g., glass) fractures with very little plastic deformation.
延性与脆性：延性材料（如铜）在断裂前发生明显塑性形变并出现颈缩；脆性材料（如玻璃）在极少塑性形变时就断裂。
6. Waves | 波
Transverse wave: a wave in which particle oscillations are perpendicular to the direction of energy propagation. Examples include electromagnetic waves and waves on a string.
横波：质点振动方向与能量传播方向垂直的波。例如电磁波和绳波。
Longitudinal wave: a wave in which particle oscillations are parallel to the direction of energy propagation, creating compressions and rarefactions. Sound waves are longitudinal.
纵波：质点振动方向与能量传播方向平行的波，形成疏部和密部。声波是纵波。
Wavelength, frequency & speed phase; frequency (f) is the number of complete oscillations per second; wave speed v = fλ.
波长、频率与波速：波长 (λ) 是两相邻同相点之间的距离；频率 (f) 是每秒完整振动的次数；波速 v = fλ。
Coherence: two wave sources are coherent if they have a constant phase difference and the same frequency. Coherence is essential for observable stationary interference patterns.
相干性：若两个波源具有恒定的相位差且频率相同，则它们是相干的。相干性是产生稳定干涉图样的必要条件。
Interference: when two or more waves superpose, the resultant amplitude is the algebraic sum of individual amplitudes. Constructive interference occurs where waves arrive in phase; destructive interference occurs where they are out of phase (phase difference of π radians).
干涉：当两列或多列波叠加时，合成振幅为各波振幅的代数和。同相相遇产生相长干涉；反相相遇（相位差 π 弧度）产生相消干涉。
Total internal reflection n : occurs when light traveling in a medium of higher refractive index strikes the boundary with a lower‑ greater than the critical angle (c). All light is reflected. sin c = 1/n for air outside.
全内反射：当光从高折射率介质射向低折射率介质，且入射角大于临界角 (c) 时，所有光都被反射。对于外部为空气，有 sin c = 1/n。
Doppler effect: the change in observed frequency when a source of waves moves relative to an observer. For sound, an approaching source gives a higher received frequency; a receding source gives a lower frequency. Used in speed cameras and astronomy.
多普勒效应：波源与观察者发生相对运动时，观察到的频率发生变化的现象。对于声波，波源靠近时接收频率变高，远离时变低。应用于测速仪和天文学。
7. Electricity | 电学
Electric current trons. The SI unit is the ampere (A). By convention, the direction of current is that of positive charge flow.
电流：电荷的流动速率，I = ΔQ/Δt。在金属中是电子的定向移动。SI 单位为安培 (A)。习惯上规定正电荷移动的方向为电流方向。
Potential difference ge to : the work done per unit charge to move charge between two points, V = W/Q. Measured in volts (V). Also called voltage.
电势差：从一点移动单位电荷到另一点所做的功，V = W/Q。单位为伏特 (V)，也叫电压。
Resistance & Ohm's law: resistance R = V/I, measured in ohms (Ω). Ohm's law states that V ∝ I provided temperature and other physical conditions remain constant. The I–V characteristic is linear for an ohmic conductor.
电阻与欧姆定律：电阻 R = V/I，单位为欧姆 (Ω)。欧姆定律指出，当温度等物理条件不变时 V ∝ I。欧姆导体的 I–V 特性为直线。
Resistivity ntrinsic property of a material governing its resistance, given by ρ = RA/L. Its unit is Ω m. Resistivity depends on temperature; for metals it increases with temperature.
电阻率：决定材料电阻的固有属性，ρ = RA/L，单位为 Ω m。电阻率与温度有关，金属的电阻率随温度升高而增大。
Kirchhoff's laws: the junction rule states that the total current entering a junction equals the total current leaving it (ΣIin = ΣIout e sum of the EMFs around any closed loop equals the sum of the potential drops (Σε = ΣIR).
基尔霍夫定律：节点电流定律指出，流入节点的总电流等于流出节点的总电流 (ΣIin = ΣIout)。回路电压定律指出，闭合回路中电动势的代数和等于电压降的代数和 (Σε = ΣIR)。
Internal resistance difference to be less than the EMF when current flows: V = ε − Ir. The lost volts are Ir.
内阻：电池或电源内部的电阻 (r)，使得有电流时端电压小于电动势：V = ε − Ir，损耗电压为 Ir。
8. Magnetism & Electromagnetism | 磁场与电磁学
Magnetic flux density (B) ector that measures the strength and direction of a magnetic field. The force on a current‑ th L carrying current I perpendicular to the field is F = BIL. B is measured in tesla (T).
磁通密度 (B)：描述磁场强弱和方向的矢量。长度为 L 且通有电流 I 的直导线与磁场垂直时，受力为 F = BIL。B 的单位为特斯拉 (T)。
Fleming's left‑hand rule: a rule that gives the direction of the force on a current‑ eld. Thumb = Force (motion), First finger = Field, Second finger = Current (conventional).
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