📚 789: Energy Resources and Efficiency | 能源与效率
Energy is essential for all life and modern society. In IGCSE Physics, understanding where energy comes from, how we use it, and how efficiently we transfer it is a core part of the syllabus. This article covers renewable and non‑renewable resources, energy transfers, efficiency calculations, and Sankey diagrams, helping you master both conceptual and calculation‑based questions.
能量对所有生命和现代社会都至关重要。在 IGCSE 物理中，理解能量从何而来、我们如何利用它以及我们传递能量的效率是课程的核心部分。本文涵盖可再生与不可再生资源、能量传递、效率计算以及桑基图，帮助你掌握概念题和计算题。
1. What is Energy? | 什么是能量？
Energy is the capacity to do work. It is a scalar quantity, measured in joules (J). Energy cannot be created or destroyed – it can only be transferred, stored or dissipated. This is the principle of conservation of energy, which underpins all energy analysis.
能量是做功的能力。它是一个标量，以焦耳（J）为单位进行测量。能量不能被创造或消灭——它只能被传递、储存或耗散。这就是能量守恒定律，是所有能量分析的基础。
In any energy transfer, the total energy before and after the event remains constant. However, energy is often dissipated as thermal energy to the surroundings, which is why 100% efficiency is almost impossible in practical systems.
在任何能量传递过程中，事件前后的总能量保持不变。然而，能量通常会以热能的形式耗散到周围环境中，这就是实际系统几乎不可能实现 100% 效率的原因。
2. Forms of Energy | 能量的形式
Energy exists in many forms. The main ones you need to recognise in IGCSE are kinetic, gravitational potential, elastic potential, thermal (internal), chemical, nuclear, electromagnetic (light), electrical, and sound energy.
能量以多种形式存在。IGCSE 需要识别的主要能量形式包括动能、重力势能、弹性势能、热（内）能、化学能、核能、电磁（光）能、电能和声能。
- Kinetic energy – energy of motion
- Gravitational potential energy – energy stored due to height above ground
- Elastic potential energy – energy stored in stretched or compressed objects
- Thermal energy – energy related to the temperature of an object
- Chemical energy – stored in bonds of molecules and released in reactions
- Nuclear energy – stored in the nucleus of atoms
- Electromagnetic energy – carried by light, microwaves, X‑rays, etc.
- Electrical energy – transferred by electric currents
- Sound energy – carried by sound waves
- 动能——运动的能量
- 重力势能——因高于地面而储存的能量
- 弹性势能——储存在被拉伸或压缩的物体中的能量
- 热能——与物体温度相关的能量
- 化学能——储存在分子键中并在反应中释放
- 核能——储存在原子核中
- 电磁能——由光、微波、X 射线等携带
- 电能——通过电流传递
- 声能——由声波携带
3. Energy Transfers and Transformations | 能量传递与转换
Energy is transferred when it moves from one store to another. For example, when a ball falls, gravitational potential energy is transferred to kinetic energy. In a battery‑powered lamp, chemical energy is transferred to electrical energy, then to light and thermal energy.
当能量从一个储存库移动到另一个储存库时，就发生了能量传递。例如，球下落时，重力势能转变为动能。在电池供电的灯中，化学能转变为电能，再转变为光能和热能。
store → thermal store. The IGCSE syllabus emphasises using energy stores rather than vague 'forms' during transfers.
用能量储存库来描述能量传递很有用：化学储存 → 动能储存 → 热能储存。IGCSE 课程强调在传递过程中使用能量储存库，而不是模糊的“形式”。
4. Renewable vs Non‑renewable Resources | 可再生与不可再生资源
Energy resources are classified as renewable or non‑renewable. Non‑renewable resources will run out one day and include fossil fuels (coal, oil, natural gas) and nuclear fuels (uranium, plutonium). Renewable resources can be replenished within a human lifespan and include solar, wind, tidal, wave, hydroelectric, geothermal, and biomass.
能源资源分为可再生和不可再生。不可再生资源终有一天会耗尽，包括化石燃料（煤、石油、天然气）和核燃料（铀、钚）。可再生资源可在人类寿命周期内得到补充，包括太阳能、风能、潮汐能、波浪能、水力发电、地热能和生物质能。
| Renewable | 可再生 | Non‑renewable | 不可再生 |
|---|---|
| Solar | 太阳能 | Coal | 煤 |
| Wind | 风能 | Oil | 石油 |
| Hydroelectric | 水力发电 | Natural gas | 天然气 |
| Tidal / Wave | 潮汐/波浪能 | Nuclear (uranium) | 核能（铀） |
| Geothermal | 地热能 | |
| Biomass | 生物质能 |
5. Fossil Fuels | 化石燃料
Fossil fuels formed from the remains of ancient plants and animals over millions of years. Coal, oil and natural gas are burned in power stations to heat water, producing steam that drives turbines generating electricity. The chemical energy store is transferred to thermal energy, then to kinetic energy in the turbine, and finally to electrical energy via the generator.
化石燃料是由数百万年前的古代动植物遗骸形成的。煤、石油和天然气在发电站中燃烧来加热水，产生蒸汽驱动涡轮机发电。化学能储存先转换为热能，然后转换为涡轮机的动能，最后通过发电机转换为电能。
The biggest drawbacks are the emission of carbon dioxide (a greenhouse gas) and sulfur dioxide (which causes acid rain). Furthermore, fossil fuels are finite and their extraction can damage the environment.
最大的缺点是会排放二氧化碳（一种温室气体）和二氧化硫（导致酸雨）。此外，化石燃料是有限的，它们的开采可能会破坏环境。
6. Nuclear Power | 核能
Nuclear power stations use nuclear fission, where uranium‑235 nuclei split, releasing a huge amount of thermal energy. This heat produces steam to turn turbines. The process does not emit carbon dioxide during operation, but it produces radioactive waste that must be stored safely for thousands of years.
核电站利用核裂变，铀‑235 原子核分裂，释放出大量热能。这些热量产生蒸汽来驱动涡轮机。该过程在运行中不排放二氧化碳，但会产生放射性废物，这些废物必须安全储存数千年。
Nuclear fuel is non‑renewable because uranium is finite. However, a small mass of uranium produces a vast amount of energy compared to fossil fuels. Public concerns about safety and waste disposal are key challenges.
核燃料是不可再生的，因为铀是有限的。然而，与化石燃料相比，少量铀能产生巨大的能量。公众对安全性和废物处理的担忧是主要的挑战。
7. Solar, Wind, and Hydroelectric | 太阳能、风能与水力发电
Solar panels convert light energy directly into electrical energy (photovoltaic) or use sunlight to heat water (solar thermal). Wind turbines convert the kinetic energy of moving air into electrical energy. Both are clean, produce no greenhouse gases during operation, but are intermittent – they depend on weather and daylight.
太阳能电池板将光能直接转换为电能（光伏），或利用阳光加热水（太阳能热利用）。风力涡轮机将流动空气的动能转换为电能。两者都是清洁的，运行中不产生温室气体，但具有间歇性——它们依赖于天气和日光。
Hydroelectric power stations capture the gravitational potential energy of water stored behind a dam. Water flows downhill, turns a turbine, and generates electricity. It provides a reliable, on‑demand renewable source, but building dams can flood large areas and disrupt ecosystems.
水力发电站捕获储存在大坝后方的水的重力势能。水向下流动，转动涡轮机，发出电力。它提供了可靠、可按需调度的可再生资源，但修建水坝可能会淹没大片区域并破坏生态系统。
8. Geothermal and Tidal Energy | 地热能与潮汐能
Geothermal energy harnesses heat from hot rocks deep underground. Cold water is pumped down, heated, and returns as steam to drive turbines. It is a reliable and low‑carbon resource, but only available in regions with volcanic or tectonic activity.
地热能利用地下深处热岩石的热量。冷水被注入地下加热后以蒸汽形式返回，驱动涡轮机。这是一种可靠且低碳的资源，但仅适用于有火山或构造活动的地区。
Tidal power uses the rise and fall of tides to turn underwater turbines or trap water in barrages. Tides are highly predictable, making it a dependable renewable source. However, constructing tidal barrages can be expensive and affect marine habitats.
潮汐能利用潮汐的涨落来驱动水下涡轮机，或将水拦在堰坝中。潮汐的可预测性很高，使其成为可靠的可再生资源。然而，建造潮汐堰坝成本高昂，且会影响海洋栖息地。
9. Efficiency of Energy Transfers | 能量传递效率
No energy transfer is perfectly efficient. Efficiency measures how much of the input energy is transferred usefully, with the rest dissipated (usually as thermal energy). High efficiency means less wasted energy and lower running costs.
没有任何能量传递是完美的。效率衡量输入能量中有多少被有用传递，其余的能量被耗散（通常为热能）。高效率意味着更少的浪费和更低的运行成本。
In IGCSE exams, you need to think about efficiency in devices like light bulbs (mostly heat), electric heaters (nearly 100% efficient for heating a room, but energy is still 'lost' as unwanted light), and internal combustion engines (significant heat loss).
在 IGCSE 考试中，你需要考虑设备如灯泡（大部分为热量）、电暖器（为房间供热时接近 100% 效率，但能量仍然会以不需要的光形式“损失”），以及内燃机（大量热量损失）的效率。
10. Calculating Efficiency | 计算效率
Efficiency can be calculated using two equivalent formulas, depending on whether you are dealing with energy or power. Both are widely used in Edexcel IGCSE questions. Remember to express efficiency as a percentage or a decimal.
效率可以用两个等价的公式计算，取决于处理的是能量还是功率。两者在 Edexcel IGCSE 考题中都被广泛使用。记住将效率表示为百分比或小数。
Efficiency = Useful energy output / Total energy input
Efficiency = Useful power output / Total power input
效率 = 有用的能量输出 / 总能量输入
效率 = 有用的功率输出 / 总功率输入
receives 500 J and does 300 J of useful mechanical work, its efficiency = (300/500) × 100% = 60%.
乘以 100 得到百分比。例如，一台电动机输入 500 J，做了 300 J 的有用机械功，其效率 = (300/500) × 100% = 60%。
11. Sankey Diagrams | 桑基图
Sankey diagrams are flow diagrams that visually represent energy transfers. The width of each arrow is proportional to the amount of energy. The useful energy output is shown as an arrow continuing to the right, while wasted energy branches downwards.
桑基图是直观表示能量传递的流程图。每个箭头的宽度与能量的大小成正比。有用的能量输出显示为向右延伸的箭头，而浪费的能量则向下分支。
For example, a filament light bulb may convert 10 J of electrical energy into only 1 J of light (useful) and 9 J of thermal energy (waste). The Sankey diagram would show a thin useful arrow and a much thicker downward waste arrow. Partial efficiency can be read from the relative widths.
例如，一个白炽灯泡可能将 10 J 电能转化为仅 1 J 的光（有用）和 9 J 的热能（浪费）。桑基图将显示一条细小的有用箭头和一条粗得多的向下浪费箭头。从宽度的相对比例可以读出效率。
IGCSE questions often ask you to calculate efficiency from a Sankey diagram or to sketch one based on given energy values.
IGCSE 考题经常要求你根据桑基图计算效率，或根据给定的能量数值画出示意图。
12. Energy Conservation and Sustainability | 能源节约与可持续性
Energy cannot be created or destroyed, but the term 'energy conservation' in everyday language means using less energy. Improving efficiency, insulating homes, using LED bulbs, and choosing appliances with high energy ratings all reduce the amount of fuel needed, lowering carbon emissions.
能量不能被创造或消灭，但日常用语中的“节约能源”意味着使用更少的能量。提高效率、为房屋加装隔热层、使用 LED 灯泡以及选择高能效等级的电器，都可以减少所需燃料，降低碳排放。
Sustainability means meeting our energy needs today without compromising the ability of future generations to meet theirs. Increasing the share of renewables, improving energy storage, and designing cities that reduce transport energy demand are all part of a sustainable future.
可持续性意味着在不损害后代满足自身需求能力的前提下，满足我们今天的能源需求。提高可再生能源占比、改进储能方式以及设计降低交通能耗的城市，都是可持续未来的组成部分。
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