📚 Topic 4.01 Energy Stores and Transfers | 4.01 能量储存与转移
Energy is a central concept in physics and is the key to explaining everything from the motion of a thrown ball to the generation of electricity. In this topic, we explore the different ways energy can be stored in a system and how it is transferred between stores when a change occurs. You will learn to identify the energy stores present before and after an event, describe the pathways by which energy is transferred, and apply the principle of conservation of energy to a wide range of situations.
能量是物理学的核心概念，也是解释从抛出的球的运动到发电等一切现象的关键。在本主题中，我们将探索能量在系统中储存的不同方式，以及当发生变化时能量如何在储存库之间转移。你将学会识别事件发生前后存在的能量储存，描述能量转移的路径，并将能量守恒原理应用到各种情境中。
1. What is Energy? | 什么是能量？
Energy is a scalar quantity that enables objects to do work. It is measured in joules (J). An object does not contain 'energy'; instead, energy is stored in various forms, and it is these stores that are transferred or converted when a process takes place. Understanding energy is about tracing where the energy comes from, where it goes, and the pathway it takes.
能量是一个标量，它使物体能够做功。能量的单位是焦耳（J）。物体并不“含有”能量；相反，能量以各种形式储存，当过程发生时，正是这些储存的能量被转移或转换。理解能量就是要追踪能量从哪里来、到哪里去，以及它经过的路径。
2. Energy Stores | 能量储存
Energy can be stored in an object or system in several distinct ways. The main stores recognised in the Edexcel IGCSE Science specification are: kinetic energy, gravitational potential energy, elastic potential energy, thermal (internal) energy, chemical energy, nuclear energy, magnetic energy and electrostatic energy. Each store is associated with a particular physical property - for example, kinetic energy is linked to an object's motion, gravitational potential energy to its height in a gravitational field, and thermal energy to the temperature and state of the particles within a substance.
能量可以以几种不同的方式储存在物体或系统中。Edexcel IGCSE 科学规范中认可的主要能量储存有：动能、重力势能、弹性势能、热（内）能、化学能、核能、磁能和静电能量。每一种储存都与一个特定的物理性质相关——例如，动能与物体的运动相关，重力势能与物体在重力场中的高度相关，热能则与物质内粒子的温度及状态相关。
| Energy Store | Description |
|---|---|
| Kinetic | Energy of a moving object |
| Gravitational potential | Energy due to an object's height in a gravitational field |
| Elastic potential | Energy stored when an object is stretched or compressed |
| Thermal (internal) | Total kinetic and potential energy of particles in a substance |
| Chemical | Energy stored in chemical bonds of fuels, food and batteries |
| Nuclear | Energy stored in the nucleus of an atom |
| Magnetic | Energy stored when like poles are pushed together or unlike poles are pulled apart |
| Electrostatic | Energy stored when charges are separated |
能量储存包括：动能、重力势能、弹性势能、热（内）能、化学能、核能、磁能和静电能量。每种储存对应于一种特定的状态或属性。
3. Energy Transfers | 能量转移
When a change happens, energy is transferred from one store to another. Energy can be transferred by four main pathways: mechanically (by a force doing work), electrically (by an electric current), by heating (due to a temperature difference) and by radiation (such as light or sound waves). In a closed system, the total energy content remains constant, but the distribution among stores can change dramatically.
当发生变化时，能量从一个储存库转移到另一个储存库。能量可以通过四种主要路径转移：机械转移（通过力做功）、电转移（通过电流）、加热转移（由于温差）和辐射转移（如光波或声波）。在一个封闭系统中，总能量保持不变，但在各储存库之间的分布可能发生显著变化。
4. Systems and Energy Changes | 系统与能量变化
A system is a set of objects or a region of space we choose to study. When we describe an energy change, we must define the system and its surroundings. For a book falling from a shelf, the system might be just the book and the Earth. As the book falls, energy is transferred from the gravitational potential store of the book-Earth system to the kinetic store of the book. The energy remains within the system, and no energy enters or leaves if we ignore air resistance.
系统是我们选择研究的一组物体或一片空间区域。描述能量变化时，我们必须定义系统及其周围环境。对于从书架上掉落的书本，系统可能只是书本和地球。书本下落时，能量从书-地球系统的重力势能储存转移到书本的动能储存。能量始终留在系统内，如果忽略空气阻力，没有能量进出。
5. Conservation of Energy | 能量守恒
The principle of conservation of energy states that energy can be transferred usefully, stored or dissipated, but it cannot be created or destroyed. This is one of the most important laws of physics. In any process, the total energy of a closed system stays the same. For example, when a moving car brakes, its kinetic energy is transferred to the thermal energy store of the brakes and the road; energy is not lost, just spread out.
能量守恒原理指出，能量可以被有效转移、储存或耗散，但不能被创造或消灭。这是物理学最重要的定律之一。在任何过程中，封闭系统的总能量保持不变。例如，行驶的汽车刹车时，其动能转移到刹车片和路面的热能储存中；能量没有消失，只是分散了。
6. Work and Energy Transfer | 功与能量转移
Work is done whenever a force moves an object. The amount of work done is equal to the energy transferred. Work done (W) is calculated as the product of the force (F) and the distance moved in the direction of the force (d). If a force does work on an object, energy is transferred to the object; if an object does work, energy is transferred away from it.
只要力使物体移动，就做了功。做功的大小等于转移的能量。功（W）等于力（F）与物体沿力的方向移动的距离（d）的乘积。如果一个力对物体做功，能量就转移到物体上；如果物体对外做功，能量就从物体转移出去。
W = F × d
Here W is measured in joules (J), F in newtons (N) and d in metres (m). Lifting a 10 N weight through 2 m does 20 J of work, transferring 20 J from the chemical store of the lifter to the gravitational potential store of the weight.
式中 W 的单位是焦耳（J），F 是牛顿（N），d 是米（m）。将一个 10 N 的重物举高 2 m，做 20 J 的功，将 20 J 能量从举者的化学能储存转移到重物的重力势能储存。
7. Gravitational Potential Energy | 重力势能
The gravitational potential energy (Eₚ) of an object depends on its mass (m), the gravitational field strength (g) and its height (h) above a reference level. On Earth, g is approximately 9.8 N/kg, but for IGCSE calculations we often use 10 N/kg. When an object is raised, work is done against gravity, and energy is transferred to its gravitational potential store.
物体的重力势能（Eₚ）取决于它的质量（m）、重力场强度（g）和相对于参考面的高度（h）。地球上的 g 值约为 9.8 N/kg，但在 IGCSE 计算中常取 10 N/kg。物体被举高时，外力克服重力做功，能量转移到它的重力势能储存中。
Eₚ = m g h
Eₚ = 2 × 10 × 3 = 60 J. If it falls, this stored energy is transferred to kinetic energy.
例如，一块 2 kg 的砖被举到 3 m 高的架子上，获得的重力势能为 Eₚ = 2 × 10 × 3 = 60 J。如果它下落，这些储存的能量将转移为动能。
8. Kinetic Energy | 动能
Any moving object possesses kinetic energy (Eₖ). The amount of kinetic energy depends on the object's mass (m) and its speed (v). The faster an object moves, the greater its kinetic energy. Because speed is squared in the formula, doubling the speed quadruples the kinetic energy, which has important safety implications for vehicles.
任何运动的物体都具有动能（Eₖ）。动能的大小取决于物体的质量（m）和速度（v）。物体运动得越快，动能越大。由于公式中速度是平方关系，速度加倍会使动能变为原来的四倍，这对车辆的安全有着重要影响。
Eₖ = ½ m v²
avelling at 15 m/s, the kinetic energy is Eₖ = 0.5 × 1200 × (15)² = 135 000 J (or 135 kJ).
一辆质量为 1200 kg 的汽车以 15 m/s 的速度行驶，其动能为 Eₖ = 0.5 × 1200 × (15)² = 135 000 J（即 135 kJ）。
9. Elastic Potential Energy | 弹性势能
When an object is stretched or compressed, work is done to deform it, and energy is stored as elastic potential energy (Eₑ). The amount stored depends on the spring constant (k) of the material and the extension (x). The equation applies as long as the object has not been stretched beyond its limit of proportionality.
当物体被拉伸或压缩时，外力做功使其变形，能量以弹性势能（Eₑ）储存。储存的能量大小取决于材料的弹簧常数（k）和伸长量（x）。只要物体未超过其比例限度，该方程均适用。
Eₑ = ½ k x²
(0.1)² = 1.0 J. This energy can be released to do work, for example, propelling a toy car.
若一个 k = 200 N/m 的弹簧被拉伸 0.1 m，则它储存的弹性势能为 Eₑ = 0.5 × 200 × (0.1)² = 1.0 J。这些能量可释放做功，例如推动一辆玩具车。
10. Thermal Energy and Heating | 热能与加热
e of the water, raising its temperature. The amount of energy needed depends on the mass, specific heat capacity and temperature change: ΔE = m c Δθ, but at this stage, the key idea is that heating is a pathway for energy transfer, not a store itself.
热能是由于物质内粒子的运动与排列而储存的内能。热能可通过加热增加，加热使能量从高温物体转移到低温物体。当我们烧水时，能量通过电或燃料燃烧转移到水的热能储存中，使其温度升高。所需能量取决于质量、比热容和温度变化：ΔE = m c Δθ，但在本阶段，核心概念是加热是一条能量转移的路径，而不是一种储存形式。
11. Power | 功率
hine that transfers a large amount of energy in a short time is said to be powerful. Power can be calculated using the equation:
功率是能量转移或做功的快慢程度。功率的单位是瓦特（W），1 W = 1 J/s。能在短时间内转移大量能量的机器被称为功率大。功率可用公式计算：
P = E / t
ifts a weight and does 300 J of work in 5 seconds, its power output is P = 300 / 5 = 60 W.
式中 P 为功率，E 为转移的能量或做的功，t 为时间。若一台电动机举升重物，在 5 秒内做 300 J 的功，则其输出功率为 P = 300 / 5 = 60 W。
12. Efficiency | 效率
No device can transfer all the input energy into useful output energy; some energy is always dissipated, usually as thermal energy to the surroundings. Efficiency measures how much of the input energy is converted to useful output. It can be expressed as a decimal or a percentage, and is always less than 100% for real machines.
没有设备能够将全部输入能量转化为有用的输出能量；总有一部分能量被耗散，通常以热能形式散失到周围环境中。效率衡量了输入能量中有多少被转化为有用的输出。效率可以用小数或百分数表示，实际机器的效率总是小于 100%。
Efficiency = (useful output energy / total input energy) × 100%
es 100 J of electrical energy to produce 15 J of light has an efficiency of (15/100) × 100% = 15% store of the surroundings. Improving efficiency reduces energy waste and saves resources.
例如，一个灯泡消耗 100 J 电能，产生 15 J 光能，则其效率为 (15/100) × 100% = 15%；剩下的 85 J 转移到周围环境的热能储存中。提高效率可以减少能源浪费，节约资源。
Published by TutorHao | Science Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图