Defining Energy | Physics | Visionlearning

<!DOCTYPE html> <html lang="en" dir="ltr"> <head>  <meta http-equiv="X-UA-Compatible" content="ie=edge"> <meta charset="utf-8"> <base href="https://www.visionlearning.com"> <title>Defining Energy | Physics | Visionlearning</title> <link rel="canonical" href="https://www.visionlearning.com/en/library/physics/24/defining-energy/199"> <meta name="description" content="Learn about the different forms of energy, including mechanical, kinetic, and potential. Includes a discussion of the work of Joule and Faraday."> <meta name="keywords" content="what are forms of energy, define work in physics, difference between kinetic and potential energy, energy conversion, how is energy measured"> <meta name="viewport" content="width=device-width, initial-scale=1.0, shrink-to-fit=no"> <meta name="msvalidate.01" content="D8E20F39AD48052260032E56DE409970"> <script type="application/ld+json"> { "@context": "http://schema.org/", "@type": "Article", "mainEntityOfPage": { "@type": "WebPage", "@id": "https://visionlearning.com/en/library/physics/24/defining-energy/199" }, "name": "Defining Energy", "headline": "Defining Energy: Forms of energy, conversions, and measuring", "author": [ { "@type": "Person", "name": "Anthony Carpi, Ph.D." } , { "@type": "Person", "name": "Zachary Hartman, Ph.D." }], "datePublished": "2014-06-19 13:00:52", "dateModified": "2017-02-12T08:30:00+05:00", "image": { "@type": "ImageObject", "url": "/img/library/moduleImages/featured_image_199-23061210061008.jpeg", "width": 696, "height": 464 }, "publisher": { "@type": "Organization", "name": "Visionlearning, Inc.", "logo": { "@type": "ImageObject", "url": "http://visionlearning.com/images/logo.png", "width": 278, "height": 60 } }, "description": "The concept of energy has fascinated scientists and philosophers for thousands of years. This module describes early ideas about energy and traces the development of our modern understanding of energy through the work of Joule and Faraday. Potential and kinetic energy are distinguished, and the six main forms of energy are described. The module highlights energy conversion and discusses how energy is measured.", "keywords": "what are forms of energy, define work in physics, difference between kinetic and potential energy, energy conversion, how is energy measured", "inLanguage": { "@type": "Language", "name": "English", "alternateName": "en" }, "copyrightHolder": { "@type": "Organization", "name": "Visionlearning, Inc." }, "copyrightYear": "2014"} </script> <meta property="og:url" content="https://visionlearning.com/en/library/physics/24/defining-energy/199"> <meta property="og:title" content="Defining Energy | Physics | Visionlearning" /> <meta property="og:type" content="website"> <meta property="og:site_name" content="Visionlearning"> <meta property="og:description" content="Learn about the different forms of energy, including mechanical, kinetic, and potential. 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href="/en/library/math-in-science/62/exponential-equations-ii/210">Exponential Equations II</a></li> <li><a href="/en/library/math-in-science/62/scientific-notation/250">Scientific Notation</a></li> <li><a href="/en/library/math-in-science/62/measurement/257">Measurement</a></li> </ul> </div> <button class="accordion__button" id="acc-button-statistics" data-accordion="button" aria-controls="acc-panel-statistics" aria-expanded="false"> <span class="accordion__button__label"> Statistics </span> </button> <div class="accordion__panel" id="acc-panel-statistics" data-accordion="panel" aria-labelledby="acc-button-statistics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/introduction-to-descriptive-statistics/218">Introduction to Descriptive Statistics</a></li> <li><a href="/en/library/math-in-science/62/introduction-to-inferential-statistics/224">Introduction to Inferential Statistics</a></li> <li><a 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role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-light-and-optics" data-accordion="button" aria-controls="acc-panel-light-and-optics" aria-expanded="false"> <span class="accordion__button__label"> Light and Optics </span> </button> <div class="accordion__panel" id="acc-panel-light-and-optics" data-accordion="panel" aria-labelledby="acc-button-light-and-optics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/physics/24/the-nature-of-light/132">The Nature of Light</a></li> <li><a href="/en/library/physics/24/electromagnetism-and-light/138">Electromagnetism and Light</a></li> </ul> </div> <button class="accordion__button" id="acc-button-mechanics" data-accordion="button" aria-controls="acc-panel-mechanics" aria-expanded="false"> <span class="accordion__button__label"> Mechanics </span> </button> <div class="accordion__panel" id="acc-panel-mechanics" data-accordion="panel" aria-labelledby="acc-button-mechanics" role="region"> <ul class="nav text-color-link"> <li class="current">Defining Energy</li> <li><a href="/en/library/physics/24/waves-and-wave-motion/102">Waves and Wave Motion</a></li> <li><a href="/en/library/physics/24/gravity/118">Gravity</a></li> <li><a href="/en/library/physics/24/thermodynamics-i/200">Thermodynamics I</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-process-of-science" data-accordion="button" aria-controls="acc-panel-process-of-science" aria-expanded="false"> <span class="accordion__button__label"> Process of Science </span> </button> <div class="accordion__panel" id="acc-panel-process-of-science" data-accordion="panel" aria-labelledby="acc-button-process-of-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-introduction" data-accordion="button" aria-controls="acc-panel-introduction" aria-expanded="false"> <span 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href="/en/library/process-of-science/49/comparison-in-scientific-research/152">Comparison in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/modeling-in-scientific-research/153">Modeling in Scientific Research</a></li> </ul> </div> <button class="accordion__button" id="acc-button-data" data-accordion="button" aria-controls="acc-panel-data" aria-expanded="false"> <span class="accordion__button__label"> Data </span> </button> <div class="accordion__panel" id="acc-panel-data" data-accordion="panel" aria-labelledby="acc-button-data" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/data-analysis-and-interpretation/154">Data Analysis and Interpretation</a></li> <li><a href="/en/library/process-of-science/49/uncertainty-error-and-confidence/157">Uncertainty, Error, and Confidence</a></li> <li><a href="/en/library/process-of-science/49/statistics-in-science/155">Statistics in Science</a></li> <li><a href="/en/library/process-of-science/49/using-graphs-and-visual-data-in-science/156">Using Graphs and Visual Data in Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-scientific-communication" data-accordion="button" aria-controls="acc-panel-scientific-communication" aria-expanded="false"> <span class="accordion__button__label"> Scientific Communication </span> </button> <div class="accordion__panel" id="acc-panel-scientific-communication" data-accordion="panel" aria-labelledby="acc-button-scientific-communication" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/understanding-scientific-journals-and-articles/158">Understanding Scientific Journals and Articles</a></li> <li><a href="/en/library/process-of-science/49/utilizing-the-scientific-literature/173">Utilizing the Scientific Literature</a></li> <li><a href="/en/library/process-of-science/49/peer-review-in-scientific-publishing/159">Peer Review in Scientific Publishing</a></li> <li><a href="/en/library/process-of-science/49/the-how-and-why-of-scientific-meetings/186">The How and Why of Scientific Meetings</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-scientists-and-research" data-accordion="button" aria-controls="acc-panel-scientists-and-research" aria-expanded="false"> <span class="accordion__button__label"> Scientists and Research </span> </button> <div class="accordion__panel" id="acc-panel-scientists-and-research" data-accordion="panel" aria-labelledby="acc-button-scientists-and-research" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-scientific-research" data-accordion="button" aria-controls="acc-panel-scientific-research" aria-expanded="false"> <span class="accordion__button__label"> Scientific Research </span> </button> <div class="accordion__panel" id="acc-panel-scientific-research" data-accordion="panel" aria-labelledby="acc-button-scientific-research" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/scientists-and-research/58/collaborative-research-in-the-arctic-towards-understanding-climate-change/183">Collaborative Research in the Arctic Towards Understanding Climate Change</a></li> <li><a href="/en/library/scientists-and-research/58/from-stable-chromosomes-to-jumping-genes/184">From Stable Chromosomes to Jumping Genes</a></li> <li><a href="/en/library/scientists-and-research/58/an-elegant-experiment-to-test-the-process-of-dna-replication/187">An Elegant Experiment to Test the Process of DNA Replication</a></li> <li><a href="/en/library/scientists-and-research/58/the-founding-of-neuroscience/233">The Founding of Neuroscience</a></li> <li><a href="/en/library/scientists-and-research/58/tracking-endangered-jaguars-across-the-border/189">Tracking Endangered Jaguars across the Border</a></li> <li><a href="/en/library/scientists-and-research/58/atmospheric-chemistry-research-that-changed-global-policy/211">Atmospheric Chemistry Research that Changed Global Policy</a></li> <li><a href="/en/library/scientists-and-research/58/revolutionizing-medicine-with-monoclonal-antibodies/220">Revolutionizing Medicine with Monoclonal Antibodies</a></li> <li><a href="/en/library/scientists-and-research/58/uncovering-the-mysteries-of-chronic-mountain-sickness/238">Uncovering the Mysteries of Chronic Mountain Sickness</a></li> </ul> </div> <button class="accordion__button" id="acc-button-profiles-in-science" data-accordion="button" aria-controls="acc-panel-profiles-in-science" aria-expanded="false"> <span class="accordion__button__label"> Profiles in Science </span> </button> <div class="accordion__panel" id="acc-panel-profiles-in-science" data-accordion="panel" aria-labelledby="acc-button-profiles-in-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/scientists-and-research/58/luis-e.-miramontes/232">Luis E. Miramontes</a></li> <li><a href="/en/library/scientists-and-research/58/bernardo-houssay/237">Bernardo Houssay</a></li> <li><a href="/en/library/scientists-and-research/58/craig-lee/256">Craig Lee</a></li> <li><a href="/en/library/scientists-and-research/58/david-ho/241">David Ho</a></li> <li><a href="/en/library/scientists-and-research/58/louis-tompkins-wright/244">Louis Tompkins Wright</a></li> <li><a href="/en/library/scientists-and-research/58/carlos-j.-finlay/217">Carlos J. Finlay</a></li> <li><a href="/en/library/scientists-and-research/58/cecilia-payne/290">Cecilia Payne</a></li> <li><a href="/en/library/scientists-and-research/58/jazmin-scarlett/291">Jazmin Scarlett</a></li> <li><a href="/en/library/scientists-and-research/58/ramari-stewart/292">Ramari Stewart</a></li> <li><a href="/en/library/scientists-and-research/58/johnson-cerda/300">Johnson Cerda</a></li> <li><a href="/en/library/scientists-and-research/58/ellen-ochoa/201">Ellen Ochoa</a></li> <li><a href="/en/library/scientists-and-research/58/ruth-benerito/205">Ruth Benerito</a></li> <li><a href="/en/library/scientists-and-research/58/franklin-chang-díaz/219">Franklin Chang Díaz</a></li> <li><a href="/en/library/scientists-and-research/58/percy-lavon-julian/221">Percy Lavon Julian</a></li> <li><a href="/en/library/scientists-and-research/58/luis-walter-alvarez/229">Luis Walter Alvarez</a></li> <li><a href="/en/library/scientists-and-research/58/france-anne-dominic-córdova/230">France Anne-Dominic Córdova</a></li> </ul> </div> </div> </div> </div> </div> </li> <li>  <button class="button" data-toggle="dropdown">Physics </button> <div class="nav__dropdown box-shadow-1 padding-1"> <div class="accordion accordion--secondary font-size-sm"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-sub-button-light-and-optics" data-accordion="button" aria-controls="acc-sub-panel-light-and-optics" aria-expanded="false"> <span class="accordion__button__label"> Light and Optics </span> </button> <div class="accordion__panel" id="acc-sub-panel-light-and-optics" data-accordion="panel" aria-labelledby="acc-sub-button-light-and-optics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/physics/24/the-nature-of-light/132">The Nature of Light</a></li> <li><a href="/en/library/physics/24/electromagnetism-and-light/138">Electromagnetism and Light</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-mechanics" data-accordion="button" aria-controls="acc-sub-panel-mechanics" aria-expanded="false"> <span class="accordion__button__label"> Mechanics </span> </button> <div class="accordion__panel" id="acc-sub-panel-mechanics" data-accordion="panel" aria-labelledby="acc-sub-button-mechanics" role="region"> <ul class="nav text-color-link"> <li class="current">Defining Energy</li> <li><a href="/en/library/physics/24/waves-and-wave-motion/102">Waves and Wave Motion</a></li> <li><a href="/en/library/physics/24/gravity/118">Gravity</a></li> <li><a href="/en/library/physics/24/thermodynamics-i/200">Thermodynamics I</a></li> </ul> </div> </div> </div> </div> </li> </ul> </nav>  <div id="theTop"></div> <main id="skip-header-content"> <div class="margin-bottom-5"> <article class="container wide module"> <header class="grid grid--sidebar-right module__header"> <div class="module__header__title"> <span class="subcategory"> <strong><em>Mechanics</em></strong> </span> <h1>Defining Energy: <sub><em>Forms of energy, conversions, and measuring</em></sub></h1> <p class="byline">by Anthony Carpi, Ph.D., Zachary Hartman, Ph.D.</p> <nav class="module__header__tabs"> <ul class="tabs-nav tabs-nav--horizontal library"> <li> <a href="/en/library/physics/24/defining-energy/199/reading" aria-current="page" >Reading</a> </li> <li> <a href="/en/library/physics/24/defining-energy/199/quiz">Quiz</a> </li> <li> <a href="/en/library/physics/24/defining-energy/199/resources">Teach with this</a> </li> </ul> </nav> </div> <script type="application/ld+json"> { "@context": "http://schema.org", "@type": "AudioObject", "contentUrl": "https://www.visionlearning.com/img/library/moduleAudio/module_199.mp3", "description": "Recording of Defining Energy : The concept of energy has fascinated scientists and philosophers for thousands of years. This module describes early ideas about energy and traces the development of our modern understanding of energy through the work of Joule and Faraday. Potential and kinetic energy are distinguished, and the six main forms of energy are described. The module highlights energy conversion and discusses how energy is measured.", "encodingFormat": "mp3", "name": "module_199.mp3" } </script> <div class="module_header_audio"> <div class="audio-player border border-radius"> <audio id="audio"> <source src="https://www.visionlearning.com/img/library/moduleAudio/module_199.mp3" type="audio/mpeg"> Your browser does not support the audio element. </audio> <div class="audio-player__title"> <p>Listen to this reading</p> <span class="audio-player__timestamp" id="timestamp"> 00:00 </span> </div> <div class="audio-player__controls" id="controls"> <button class="button button--icon-only" id="play-pause-button"> <span class="icon icon-play" aria-hidden="true"></span> </button> <div class="audio-player__progress" id="progress-bar" tabindex="0" aria-valuemin="0" aria-valuemax="100" aria-valuenow="0" aria-label="Use arrow keys to forward or rewind the audio" role="slider"> <div class="audio-player__progress__fill"> <span class="audio-player__thumb"></span> </div> </div> <div class="audio-player__volume-container"> <button id="mute-button"> <span class="icon icon-volume"></span> </button> <div class="audio-player__volume" tabindex="0" aria-valuemin="0" aria-valuemax="100" aria-valuenow="100" aria-label="Use arrow keys to adjust volume" role="slider"> <div class="audio-player__volume__fill"> <span class="audio-player__thumb"></span> </div> </div> </div> </div> </div> </div> </header> <hr class="divider"/>   <div class="grid grid--sidebar-right grid--divider"> <div class="order-2 order-1--lg module__main"> <div class="narrow margin-x-auto margin-y-5"> <div class="accordion margin-bottom-5">  <button class="accordion__button" id="acc-button-key-concepts" data-accordion="button" aria-controls="acc-panel-key-concepts" aria-expanded="true" tabindex="0"> Did you know? </button> <div class="accordion__panel shown show" id="acc-panel-key-concepts" data-accordion="panel" aria-labelledby="acc-button-key-concepts" role="region"> <div class="accordion__panel__content"> <p>Did you know that when you warm your hands by rubbing them together fast, you are changing energy from one form to another? There are many different forms of energy, any of which can be changed into other forms. This conversion of energy is what makes all of our daily activities possible.</p> </div> </div>  <button class="accordion__button" id="acc-button-table-of-contents" data-accordion="button" aria-controls="acc-panel-table-of-contents" aria-expanded="false" tabindex="0"> Key concepts </button> <div class="accordion__panel" id="acc-panel-table-of-contents" data-accordion="panel" aria-labelledby="acc-button-table-of-contents" role="region" aria-hidden="true"> <div class="accordion__panel__content"> <ul class="bulleted"> <li><p>Energy is defined as the capacity to perform work.</p></li> <li><p>Energy comes in many forms, such as mechanical, chemical, heat, etc. and all are interchangeable to some extent.</p></li> <li><p>James Joule was instrumental in establishing the concept of interchangeability of different forms of energy and quantitatively measured those changes in certain systems.</p></li> </ul> </div> </div>  <button class="accordion__button" id="acc-button-terms-you-should-know" data-accordion="button" aria-controls="acc-panel-terms-you-should-know" aria-expanded="false" tabindex="0"> Terms you should know </button> <div class="accordion__panel" id="acc-panel-terms-you-should-know" data-accordion="panel" aria-labelledby="acc-button-terms-you-should-know" role="region" aria-hidden="true"> <div class="accordion__panel__content"> <dl> <dt>field of force </dt> <dd> the area around one object in which it can exert influence on another object </dd> <dt><a href="/en/glossary/view/kinetic">kinetic </a></dt> <dd> relating to the motion of objects </dd> <dt><a href="/en/glossary/view/thermal">thermal </a></dt> <dd> relating to heat </dd> <dt><a href="/en/glossary/view/work">work </a></dt> <dd> using force to move an object; a process in which one form of energy is converted into another</dd> </dl> </div> </div> </div> <hr class="border-color-dark" /> <section> <div class="container narrow"> <p>Energy touches upon everything we do. From the lights we turn on in the morning, to the car we drive to work or school, to our ability to read this page. <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">Energy</mark> is both a constant in the human existence while also representing the process of change. All of our daily activities are possible because of the conversion of one form of energy to another. As such, scientists and even philosophers through the ages have tried to understand and come to terms with the concept. Yet until recently, a clear understanding of energy has escaped us. So how did we come to understand it?</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox="" data-lightbox-src="/img/library/large_images/image_3066.jpg"> <img src="/img/library/modules/mid199/Image/VLObject-3066-041201021211.jpg" alt="Figure 1: Ancient Greek philosophers thought that all matter and processes could be described in terms of combinations of four elements: earth, air, water, and fire." /> </button> <figcaption> <p><strong>Figure 1</strong>: Ancient Greek philosophers thought that all matter and processes could be described in terms of combinations of four elements: earth, air, water, and fire.</p> </figcaption> </figure> </div> <p>The four-element <mark class="term" data-term="theory" data-term-def="A scientific theory is an explanation inferred from multiple lines of evidence for some broad aspect of the natural world and&hellip;" data-term-url="/en/glossary/view/theory/4854">theory</mark> was championed by <mark class="term" data-term="Aristotle" data-term-def="A Greek philosopher born in Stagira (384-322 BCE). He joined Plato's Academy in Athens (then being run by Eudoxus) at the&hellip;" data-term-url="/en/glossary/view/Aristotle/4466">Aristotle</mark> and other influential philosophers of Ancient Greece, but in practice this theory provided a very poor framework by which we could come to understand the <mark class="term" data-term="universe" data-term-def="The cosmos and everything that exists in it." data-term-url="/en/glossary/view/universe/5288">universe</mark>, especially with respect to <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark>. Yet due to Aristotle’s influence, the philosophy held strong against all challengers for almost 2,000 years. A true understanding of energy eluded Western science throughout most of the <mark class="term" data-term="Middle Ages" data-term-def="European history from the 5th century to the 15th century. The Middle Ages follow the fall of the Western Roman Empire&hellip;" data-term-url="/en/glossary/view/Middle+Ages/5329">Middle Ages</mark>.</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox="" data-lightbox-src="/img/library/large_images/image_2702.jpg"> <img src="/img/library/modules/mid199/Image/VLObject-2702-081105121145.jpg" alt="Figure 2: Sir Isaac Newton" /> </button> <figcaption> <p><strong>Figure 2</strong>: Sir Isaac Newton</p> </figcaption> </figure> </div> <p>In 1687, the legendary scientist <mark class="term" data-term="Isaac Newton" data-term-def="English alchemist, physicist, astronomer and mathematician born in Woolsthorpe-by-Colsterworth, Lincolnshire (1643-1727). In 1672, Newton offered an experimental proof that light is&hellip;" data-term-url="/en/glossary/view/Isaac+Newton/3725">Isaac Newton</mark> (see Figure 2) published his <em>Mathematical Principles of Natural Philosophy</em> (casually known as the <em>Principia</em>), in which he described the <mark class="term" data-term="law" data-term-def="In science, a principle that describes a phenomenon, often mathematically." data-term-url="/en/glossary/view/law/8686">laws</mark> governing bodies in motion. The <em>Principia</em> gave a thorough, mathematical description of the laws of motion, providing the first accurate description of the <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> associated with moving objects: <mark class="term" data-term="mechanical" data-term-def="Involving physical force or motion." data-term-url="/en/glossary/view/mechanical/8516">mechanical</mark> energy. Since Newton’s time, scientists have described in great detail other major forms of energy, including <mark class="term" data-term="thermal" data-term-def="Relating to heat." data-term-url="/en/glossary/view/thermal/8682">thermal</mark>, chemical, electrical, electromagnetic, and nuclear.</p> <p><section id="toc_1" class=""> <h2>What is energy?</h2></p> <p>At its foundation, <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> is a very simple concept. The term was first invented by <mark class="term" data-term="Thomas Young" data-term-def="English physicist and physician, born in Milverton, Somerset (1773-1829). Young's experiments with deflecting light showed interference patterns, proving that light is&hellip;" data-term-url="/en/glossary/view/Young%2C+Thomas/4514">Thomas Young</mark> in 1807 after the Greek word <em>energeia</em>, which roughly translates to “activity.” Energy is the ability for an object to perform <mark class="term" data-term="work" data-term-def="A process that occurs when a force acts over a distance, as when an object is moved. Work equals the multiple&hellip;" data-term-url="/en/glossary/view/work/1502">work</mark> on another object. At its core, this is a simple definition; however, it can manifest itself in many ways.</p></section> <section id="toc2_1"><h3>Mechanical energy</h3><p>Mechanical <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> is the energy possessed by an object because of its movement or position. We often describe <mark class="term" data-term="mechanical" data-term-def="Involving physical force or motion." data-term-url="/en/glossary/view/mechanical/8516">mechanical</mark> energy in two different forms, potential and <mark class="term" data-term="kinetic" data-term-def="Relating to the motion of objects." data-term-url="/en/glossary/view/kinetic/8681">kinetic</mark>. <mark class="term" data-term="potential energy" data-term-def="The energy an object possesses by virtue of its position in relation to a field of force. For example, lifting&hellip;" data-term-url="/en/glossary/view/potential+energy/1504">Potential energy</mark> is so-called “stored” energy because it is the energy an object possesses as a result of its position in relation to a field of <mark class="term" data-term="force" data-term-def="An influence (a "push or pull") that changes the motion of a moving object (e.g., slows it down, speeds it up,&hellip;" data-term-url="/en/glossary/view/force/883">force</mark>, such as <mark class="term" data-term="gravity" data-term-def="The natural force that attracts a body toward the center of the Earth, or toward another physical body having mass." data-term-url="/en/glossary/view/gravity/11223">gravity</mark>. For example, when we lift a ball off the ground into the air, the object gains potential energy as it is moving to a position in which gravity will cause it to drop to the ground if we release it. If we then drop the ball, the potential energy that is present is converted into <mark class="term" data-term="kinetic energy" data-term-def="The energy an object possesses by virtue of its motion. An object of mass m moving at velocity v has a&hellip;" data-term-url="/en/glossary/view/kinetic+energy/1505">kinetic energy</mark>, which is the energy associated with the motion of an object. The concepts of potential and kinetic energy do not apply only to mechanical energy. A battery that is not connected to a circuit is considered to have potential energy that can be converted to electrical energy if the circuit is closed. Potential energy is found in other energy forms, as well.</p><p>The conversion of potential into <mark class="term" data-term="kinetic" data-term-def="Relating to the motion of objects." data-term-url="/en/glossary/view/kinetic/8681">kinetic</mark> <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> is demonstrated in the following example using a weight and pulley (see concept simulation below). As the individual lifts the weight against the <mark class="term" data-term="force" data-term-def="An influence (a "push or pull") that changes the motion of a moving object (e.g., slows it down, speeds it up,&hellip;" data-term-url="/en/glossary/view/force/883">force</mark> of <mark class="term" data-term="gravity" data-term-def="The natural force that attracts a body toward the center of the Earth, or toward another physical body having mass." data-term-url="/en/glossary/view/gravity/11223">gravity</mark>, the <mark class="term" data-term="potential energy" data-term-def="The energy an object possesses by virtue of its position in relation to a field of force. For example, lifting&hellip;" data-term-url="/en/glossary/view/potential+energy/1504">potential energy</mark> rises. Dropping the weight will convert this potential energy into <mark class="term" data-term="kinetic energy" data-term-def="The energy an object possesses by virtue of its motion. An object of mass m moving at velocity v has a&hellip;" data-term-url="/en/glossary/view/kinetic+energy/1505">kinetic energy</mark> momentarily as the object is falling. The higher we lift the object, the more potential energy we impart as it is further from the <mark class="term" data-term="surface" data-term-def="The outside or external part; the topside face of something." data-term-url="/en/glossary/view/surface/8275">surface</mark> of the Earth, and so the more kinetic energy it releases as it falls. You can try this <mark class="term" data-term="experiment" data-term-def="A test or trial carried out under controlled conditions so that specific actions can be performed and the results can be observed." data-term-url="/en/glossary/view/experiment/8292">experiment</mark> yourself; the link below allows you to lift and drop a 100-kg weight. You can observe how potential and kinetic energy are related to each other by “freezing” the weight at different heights during its fall.</p></section> <section id="toc2_2"><h3>Thermal energy</h3><p>Thermal <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> is also associated with motion, but in this case it is the motion of objects at the atomic level. <mark class="term" data-term="thermal" data-term-def="Relating to heat." data-term-url="/en/glossary/view/thermal/8682">Thermal</mark> energy is derived from the <mark class="term" data-term="kinetic" data-term-def="Relating to the motion of objects." data-term-url="/en/glossary/view/kinetic/8681">kinetic</mark> energy of <mark class="term" data-term="atom" data-term-def="The smallest unit of an element that retains the chemical properties of the element. Atoms can exist alone or in&hellip;" data-term-url="/en/glossary/view/atom/1509">atoms</mark> or <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecules</mark> within a <mark class="term" data-term="system" data-term-def="A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for&hellip;" data-term-url="/en/glossary/view/system/3904">system</mark>. In other words, the atoms and molecules of all substances are in constant motion at any temperature above <mark class="term" data-term="absolute zero" data-term-def="The theoretical lowest temperature possible at which all molecular motion ceases. Absolute zero, 0 K or -273.15°C, has never been reached." data-term-url="/en/glossary/view/absolute+zero/1523">absolute zero</mark>, and this is true even for <mark class="term" data-term="solid" data-term-def="A collection of atoms or molecules that are held together so that, under constant conditions, they maintain a defined shape and&hellip;" data-term-url="/en/glossary/view/solid/7571">solids</mark>. The thermal energy of a material, as measured by its temperature, is related to the motion of the atoms and molecules within that material – hot materials contain molecules moving very rapidly, while colder materials have molecules moving more slowly.</p><p>So what’s the difference between <mark class="term" data-term="thermal" data-term-def="Relating to heat." data-term-url="/en/glossary/view/thermal/8682">thermal</mark> and <mark class="term" data-term="mechanical" data-term-def="Involving physical force or motion." data-term-url="/en/glossary/view/mechanical/8516">mechanical</mark> energy? Put simply, it’s the <mark class="term" data-term="scale" data-term-def="An instrument for measuring heat energy or weight in which units are marked at intervals; a system for quantifying heat energy&hellip;" data-term-url="/en/glossary/view/scale/8536">scale</mark> of the problem. For example, if you touch a hot pan, the <mark class="term" data-term="atom" data-term-def="The smallest unit of an element that retains the chemical properties of the element. Atoms can exist alone or in&hellip;" data-term-url="/en/glossary/view/atom/1509">atoms</mark> of metal are moving very quickly, and they can transfer the thermal <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> on that atomic level, causing pain and even burns. Mechanical energy is the energy released when you drop the pan because it is hot.</p></section> <section id="toc2_3"><h3>Chemical energy</h3><p>Chemical <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> is also related to <mark class="term" data-term="atom" data-term-def="The smallest unit of an element that retains the chemical properties of the element. Atoms can exist alone or in&hellip;" data-term-url="/en/glossary/view/atom/1509">atoms</mark> and <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecules</mark>, but it is a function of their structure and interaction as opposed to their motion. As described in our <a href="/en/library/Chemistry/1/Chemical-Bonding/55">Chemical Bonding</a> module, atoms and molecules can <mark class="term" data-term="bond" data-term-def="The force that holds together units such as atoms or molecules. <br> <b>[verb]</b> To hold or fasten units such as atoms or molecules together." data-term-url="/en/glossary/view/bond/8297">bond</mark> with one another as a result of their <mark class="term" data-term="electron" data-term-def="A subatomic particle with a negative charge of 1.60 × 10<sup>-19</sup> coulombs and a mass of 9.11 × 10<sup>-31</sup> kg. Electrons&hellip;" data-term-url="/en/glossary/view/electron/852">electron</mark> structure. Similar to when we lift or drop an object within a gravitational field of <mark class="term" data-term="force" data-term-def="An influence (a "push or pull") that changes the motion of a moving object (e.g., slows it down, speeds it up,&hellip;" data-term-url="/en/glossary/view/force/883">force</mark>, the <mark class="term" data-term="bonding" data-term-def="The act of fastening two atoms together." data-term-url="/en/glossary/view/bonding/8295">bonding</mark> of two atoms represents an interaction within an electromagnetic field of force. And this interaction results in a change of energy. In some cases chemical changes require the input of energy, while in other cases chemical changes give off energy in the form of <mark class="term" data-term="heat" data-term-def="A measure of the total internal energy of a substance that can be increased or decreased when objects with different temperatures&hellip;" data-term-url="/en/glossary/view/heat/1506">heat</mark>, <mark class="term" data-term="mechanical" data-term-def="Involving physical force or motion." data-term-url="/en/glossary/view/mechanical/8516">mechanical</mark> energy (such as during an explosion), or electrical energy (such as in a battery).</p></section> <section id="toc2_4"><h3>Nuclear energy</h3><p>Atoms also contain <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> stored as a function of their internal structures. Within the <mark class="term" data-term="nucleus" data-term-def="1. [Atomic] A tiny, dense positively charged mass at the heart of an atom. The nucleus is composed of protons and&hellip;" data-term-url="/en/glossary/view/nucleus/1526">nucleus</mark> of the <mark class="term" data-term="atom" data-term-def="The smallest unit of an element that retains the chemical properties of the element. Atoms can exist alone or in&hellip;" data-term-url="/en/glossary/view/atom/1509">atom</mark>, the strong nuclear <mark class="term" data-term="force" data-term-def="An influence (a "push or pull") that changes the motion of a moving object (e.g., slows it down, speeds it up,&hellip;" data-term-url="/en/glossary/view/force/883">force</mark> keeps <mark class="term" data-term="proton" data-term-def="A subatomic (ß link to atom) particle with a positive charge of 1.60 × 10<sup>-19</sup> coulombs and a mass of 1.672&hellip;" data-term-url="/en/glossary/view/proton/854">protons</mark> and <mark class="term" data-term="neutron" data-term-def="A sub-atomic particle with no charge and a mass of 1.675 × 10<sup>-27</sup> kg. Neutrons are found in the nucleus&hellip;" data-term-url="/en/glossary/view/neutron/1520">neutrons</mark> bound together. The breaking or forming of these nuclear interactions can take up or release nuclear energy. These processes can occur naturally, as when a radioactive <mark class="term" data-term="element" data-term-def="One of fewer than 118 pure chemical substances. An element is a substance composed of atoms with identical atomic number." data-term-url="/en/glossary/view/element/1510">element</mark> like uranium <mark class="term" data-term="decay" data-term-def="To break down; to decrease over time in size, amount, or force." data-term-url="/en/glossary/view/decay/8265">decays</mark>. In fact, the <mark class="term" data-term="heat" data-term-def="A measure of the total internal energy of a substance that can be increased or decreased when objects with different temperatures&hellip;" data-term-url="/en/glossary/view/heat/1506">heat</mark> from naturally-occurring radioactive elements in the Earth’s <mark class="term" data-term="crust" data-term-def="The uppermost 5-70 km of the Earth. There are two types of crust: continental and oceanic. Continental crust ranges from 10-70&hellip;" data-term-url="/en/glossary/view/crust/880">crust</mark> contributes substantially to the production of heat at the Earth’s <mark class="term" data-term="core" data-term-def="The innermost layer of the Earth, which starts at ~2900 km depth. The core is composed mainly of iron and consists&hellip;" data-term-url="/en/glossary/view/core/1663">core</mark>. They can also be stimulated to occur artificially, and the nuclear energy released by these stimulated radioactive processes is what powers nuclear power plants.</p></section> <section id="toc2_5"><h3>Electromagnetic energy</h3><p>Another form of <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> is associated with <mark class="term" data-term="particle" data-term-def="A tiny piece of matter." data-term-url="/en/glossary/view/particle/8259">particles</mark> even smaller than <mark class="term" data-term="atom" data-term-def="The smallest unit of an element that retains the chemical properties of the element. Atoms can exist alone or in&hellip;" data-term-url="/en/glossary/view/atom/1509">atoms</mark>. Electromagnetic energy is caused by the motion of photons, which are packets of energy that behave both like particles and like <mark class="term" data-term="waves" data-term-def="The motion of rising and falling in curves; undulation." data-term-url="/en/glossary/view/waves/8274">waves</mark>. Photons make up all the forms of <mark class="term" data-term="electromagnetic radiation" data-term-def="A series of waves that are propagated by simultaneous, periodic variations of electrical and magnetic fields. Examples of electromagnetic radiation include&hellip;" data-term-url="/en/glossary/view/electromagnetic+radiation/1501">electromagnetic radiation</mark> that we are familiar with, like visible, infrared, and <mark class="term" data-term="ultraviolet" data-term-def="Wavelengths between 1 and 380 nanometers (nm) on the electromagnetic spectrum, falling between X-rays (10<sup>-2</sup> nm to 1 nm) and visible&hellip;" data-term-url="/en/glossary/view/ultraviolet/8233">ultraviolet</mark> <mark class="term" data-term="light" data-term-def="A form of electromagnetic radiation. Visible light is that associated with stimulating the organs of sight, which for normal human&hellip;" data-term-url="/en/glossary/view/light/1498">light</mark>, radio <mark class="term" data-term="waves" data-term-url="/en/glossary/view/waves" data-term-def="The motion of rising and falling in curves; undulation.">waves</mark>, and microwaves, as well as those we might be less familiar with, like gamma <mark class="term" data-term="radiation" data-term-def="Energy emitted as particles, waves, or rays." data-term-url="/en/glossary/view/radiation/8266">radiation</mark>. Electromagnetic energy often causes changes in the energy level of <mark class="term" data-term="electron" data-term-def="A subatomic particle with a negative charge of 1.60 × 10<sup>-19</sup> coulombs and a mass of 9.11 × 10<sup>-31</sup> kg. Electrons&hellip;" data-term-url="/en/glossary/view/electron/852">electrons</mark> within atoms, or the motion of atoms and <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecules</mark>. For example, water molecules can <mark class="term" data-term="absorb" data-term-def="Take in or soak up (energy, liquids, or other substances), usually gradually, through a chemical or physical action." data-term-url="/en/glossary/view/absorb/11219">absorb</mark> microwave radiation, which causes them to vibrate, increasing their <mark class="term" data-term="thermal" data-term-def="Relating to heat." data-term-url="/en/glossary/view/thermal/8682">thermal</mark> energy, and heating your food in the process. And ultraviolet waves can cause damage to the molecules in your skin itself, causing a sunburn even in the absence of thermal energy.</p></section> <section id="toc2_6"><h3>Electrical energy</h3><p>Electrical <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> also is based in the movement of <mark class="term" data-term="particle" data-term-def="A tiny piece of matter." data-term-url="/en/glossary/view/particle/8259">particles</mark> associated with <mark class="term" data-term="atom" data-term-def="The smallest unit of an element that retains the chemical properties of the element. Atoms can exist alone or in&hellip;" data-term-url="/en/glossary/view/atom/1509">atoms</mark>, but in this case it is the flow of <mark class="term" data-term="electron" data-term-def="A subatomic particle with a negative charge of 1.60 × 10<sup>-19</sup> coulombs and a mass of 9.11 × 10<sup>-31</sup> kg. Electrons&hellip;" data-term-url="/en/glossary/view/electron/852">electrons</mark> within a <mark class="term" data-term="system" data-term-def="A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for&hellip;" data-term-url="/en/glossary/view/system/3904">system</mark>. Electrical energy can be generated in a number of ways. For example, certain <mark class="term" data-term="chemical reaction" data-term-def="A process in which atoms and molecules recombine by forming or breaking chemical bonds. Chemical reactions form new products that&hellip;" data-term-url="/en/glossary/view/chemical+reaction/1547">chemical reactions</mark>, such as those that take place in batteries, cause electrons to flow. In addition, physically moving a conductor like a metal in a magnetic field can generate electrical <mark class="term" data-term="current" data-term-def="a flow, as of electricity or water. In oceanography and hydrology, a channel of water that flows together at the same velocity" data-term-url="/en/glossary/view/current/8278">current</mark>. And <mark class="term" data-term="light" data-term-def="A form of electromagnetic radiation. Visible light is that associated with stimulating the organs of sight, which for normal human&hellip;" data-term-url="/en/glossary/view/light/1498">light</mark> can also stimulate the flow of electrons in certain materials, such as photovoltaic cells. Once electrical current is generated, it can flow through materials that have “loosely” attached electrons, specifically metals, making them good conductors of electricity.</p></section> <section id="toc2_7"><h3>Other forms of energy</h3><p>While we are most likely to encounter these six forms of <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> in daily life, they are not the only ways that energy can be seen. In general, however, other forms of energy are really special descriptions of the six forms we've discussed. Sound energy, for example, can create concussive <mark class="term" data-term="force" data-term-def="An influence (a "push or pull") that changes the motion of a moving object (e.g., slows it down, speeds it up,&hellip;" data-term-url="/en/glossary/view/force/883">forces</mark> through vibration of air <mark class="term" data-term="particle" data-term-def="A tiny piece of matter." data-term-url="/en/glossary/view/particle/8259">particles</mark>. This is really a specific form of <mark class="term" data-term="mechanical" data-term-def="Involving physical force or motion." data-term-url="/en/glossary/view/mechanical/8516">mechanical</mark> energy. The key point is that you will encounter energy in a large variety of ways.</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc6766"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">__________ energy has to do with the motion of molecules, while __________ energy has to do with the flow of electrons.</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-6766-0-option-a" name="quiz-option-6766" type="radio" value="Thermal, electrical" > <span class="option__label"> <span class="screen-reader-only">a.</span> Thermal, electrical </span> </label> <span class="quiz__response" id="response-6766-0"> <strong>Correct!</strong> </span> </div> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-6766-1-option-b" name="quiz-option-6766" type="radio" value="Mechanical, nuclear" > <span class="option__label"> <span class="screen-reader-only">b.</span> Mechanical, nuclear </span> </label> <span class="quiz__response" id="response-6766-1"> <strong>Incorrect.</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_2"> <h2>James Joule and the conversion of energy</h2><p>Energy manifests in so many different forms that at first glance it may seem impossible to relate them. In fact, for a long time scientists thought each form of <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> represented a unique <mark class="term" data-term="property" data-term-def="A characteristic or attribute." data-term-url="/en/glossary/view/property/8555">property</mark> about the <mark class="term" data-term="universe" data-term-def="The cosmos and everything that exists in it." data-term-url="/en/glossary/view/universe/5288">universe</mark>. For example, it was thought that <mark class="term" data-term="work" data-term-def="A process that occurs when a force acts over a distance, as when an object is moved. Work equals the multiple&hellip;" data-term-url="/en/glossary/view/work/1502">work</mark> (mechanical energy) and <mark class="term" data-term="heat" data-term-def="A measure of the total internal energy of a substance that can be increased or decreased when objects with different temperatures&hellip;" data-term-url="/en/glossary/view/heat/1506">heat</mark> (thermal energy) were two completely separate entities!</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox="" data-lightbox-src="/img/library/large_images/image_6790.jpg"> <img src="/img/library/modules/mid199/Image/VLObject-6790-140605100614.jpg" alt="Figure 3: James Joule" /> </button> <figcaption> <p><strong>Figure 3</strong>: James Joule</p> </figcaption> </figure> </div> <p>This concept of separate forms of <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> was finally successfully challenged by James Prescott Joule (1818–1889), a Scottish chemist who contributed several important experimental findings to our understanding of energy (Figure 3). His most famous <mark class="term" data-term="experiment" data-term-def="A test or trial carried out under controlled conditions so that specific actions can be performed and the results can be observed." data-term-url="/en/glossary/view/experiment/8292">experiment</mark>, published in 1845, used a paddle wheel to show that different forms of energy are interchangeable. This concept was not entirely discovered by Joule; several researchers attempted to demonstrate that <mark class="term" data-term="heat" data-term-def="A measure of the total internal energy of a substance that can be increased or decreased when objects with different temperatures&hellip;" data-term-url="/en/glossary/view/heat/1506">heat</mark> and energy were interconvertible before Joule, but their experiments were poorly designed, leading to ambiguous results that were challenged. Joule, through diligent planning and careful measurement, was the first scientist to back this concept with solid <mark class="term" data-term="data" data-term-def="(plural form of <b>datum</b>) A collection of pieces of information, generally taking the form of numbers, text, bits, or facts, that&hellip;" data-term-url="/en/glossary/view/data/3729">data</mark>. To do this, Joule built a special pulley system and a sealed water vessel that was insulated from the <mark class="term" data-term="environment" data-term-def="The conditions that surround and affect an organism." data-term-url="/en/glossary/view/environment/8270">environment</mark>. He used a <mark class="term" data-term="system" data-term-def="A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for&hellip;" data-term-url="/en/glossary/view/system/3904">system</mark> of weights to perform a precise amount of <mark class="term" data-term="work" data-term-def="A process that occurs when a force acts over a distance, as when an object is moved. Work equals the multiple&hellip;" data-term-url="/en/glossary/view/work/1502">work</mark> on the paddle wheel, which, in turn, caused the water in the vessel to move. The <mark class="term" data-term="friction" data-term-def="the force resisting the movement of one surface over another. Friction acts at the interface of solids, fluid, and gases" data-term-url="/en/glossary/view/friction/12611">friction</mark> associated with stirring the water inside a vessel raised the temperature of the water, which could be measured using a thermometer. His experimental data showed that a weight of 772 pounds falling one foot would raise the temperature of one pound of water by one <mark class="term" data-term="degree" data-term-def="[<strong>temperature</strong>] One graduated unit of measure on a Fahrenheit or Celsius temperature scale. On the Kelvin scale, graduations are called Kelvins. <br> <br> [<strong>geometry</strong>]&hellip;" data-term-url="/en/glossary/view/degree/8535">degree</mark> Fahrenheit. In doing this, Joule was the first to clearly demonstrate beyond the shadow of a doubt that <mark class="term" data-term="mechanical" data-term-def="Involving physical force or motion." data-term-url="/en/glossary/view/mechanical/8516">mechanical</mark> energy could be changed into <mark class="term" data-term="thermal" data-term-def="Relating to heat." data-term-url="/en/glossary/view/thermal/8682">thermal</mark> energy.</p><p>In many ways, this concept of transforming motion into <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> is very obvious to us in modern times. If you rub your hands together, they get hotter due to <mark class="term" data-term="friction" data-term-def="the force resisting the movement of one surface over another. Friction acts at the interface of solids, fluid, and gases" data-term-url="/en/glossary/view/friction/12611">friction</mark>. It’s important to note, however, that scientists of James Joule’s day did not find this concept intuitive. They thought that <mark class="term" data-term="heat" data-term-def="A measure of the total internal energy of a substance that can be increased or decreased when objects with different temperatures&hellip;" data-term-url="/en/glossary/view/heat/1506">heat</mark> was caused by a substance stored within hot objects called “caloric,” and as this substance moved, you could get <mark class="term" data-term="work" data-term-def="A process that occurs when a force acts over a distance, as when an object is moved. Work equals the multiple&hellip;" data-term-url="/en/glossary/view/work/1502">work</mark> (for more about the caloric <mark class="term" data-term="theory" data-term-def="A scientific theory is an explanation inferred from multiple lines of evidence for some broad aspect of the natural world and&hellip;" data-term-url="/en/glossary/view/theory/4854">theory</mark> of heat, refer to our <a href="/en/library/Physics/24/Thermodynamics-I/200">Thermodynamics I</a> module). By understanding that <mark class="term" data-term="thermal" data-term-def="Relating to heat." data-term-url="/en/glossary/view/thermal/8682">thermal</mark> energy and <mark class="term" data-term="mechanical" data-term-def="Involving physical force or motion." data-term-url="/en/glossary/view/mechanical/8516">mechanical</mark> energy were two different forms of the same thing, Joule demonstrated a critical concept and added greatly to our understanding of energy.</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox="" data-lightbox-src="/img/library/large_images/image_7172.jpg"> <img src="/img/library/modules/mid199/Image/VLObject-7172-140922020904.jpg" alt="Figure 4: Michael Faraday" /> </button> <figcaption> <p><strong>Figure 4</strong>: Michael Faraday</p> </figcaption> </figure> </div> <p>Interestingly, the idea that forms of <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> could not be converted was not limited to the interplay between <mark class="term" data-term="mechanical" data-term-def="Involving physical force or motion." data-term-url="/en/glossary/view/mechanical/8516">mechanical</mark> and <mark class="term" data-term="thermal" data-term-def="Relating to heat." data-term-url="/en/glossary/view/thermal/8682">thermal</mark> energy. Prior to the 1800s, the relationship between electricity, <mark class="term" data-term="magnetism" data-term-def="Forces of attraction or repulsion between objects." data-term-url="/en/glossary/view/magnetism/8279">magnetism</mark>, and <mark class="term" data-term="light" data-term-def="A form of electromagnetic radiation. Visible light is that associated with stimulating the organs of sight, which for normal human&hellip;" data-term-url="/en/glossary/view/light/1498">light</mark> eluded scientists. They were each said to require a different “ether” and had unique properties. This changed, however, when <mark class="term" data-term="Michael Faraday" data-term-def="British chemist and physicist born in London (1791-1867). In 1831, Faraday discovered electromagnetic induction, the principle by which electric transformers and&hellip;" data-term-url="/en/glossary/view/Faraday%2C+Michael/4515">Michael Faraday</mark> (shown in Figure 4) invented the electric generator in 1821. Faraday had been experimenting with devices to maintain a constant electric <mark class="term" data-term="current" data-term-def="a flow, as of electricity or water. In oceanography and hydrology, a channel of water that flows together at the same velocity" data-term-url="/en/glossary/view/current/8278">current</mark>. He found that he could achieve this by rotating a copper disk within a magnetic field. Remarkably, he found that he could cause the opposite effect as well: Running a current through the disk triggered the disc to rotate. Faraday was able to demonstrate that, with the right design, this rotation could be used to power a shaft. Faraday had invented a precursor to the electric motor and in doing so was one of the first scientists to show that electrical and mechanical energy could be interconverted.</p><p>Certainly, there are many different ways to convert <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark>. Describing each could fill volumes of books: <mark class="term" data-term="heat" data-term-def="A measure of the total internal energy of a substance that can be increased or decreased when objects with different temperatures&hellip;" data-term-url="/en/glossary/view/heat/1506">Heat</mark> released by nuclear energy drives the formation of steam and is used to turn giant turbines to generate electricity, our body uses chemical energy to power our muscles, and the list goes on. It is possible to transform any form of energy into any other.</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc6773"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">Which scientist was the first to definitively show that mechanical energy could be converted into thermal energy?</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-6773-0-option-a" name="quiz-option-6773" type="radio" value="Joule" > <span class="option__label"> <span class="screen-reader-only">a.</span> Joule </span> </label> <span class="quiz__response" id="response-6773-0"> <strong>Incorrect.</strong> </span> </div> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-6773-1-option-b" name="quiz-option-6773" type="radio" value="Faraday" > <span class="option__label"> <span class="screen-reader-only">b.</span> Faraday </span> </label> <span class="quiz__response" id="response-6773-1"> <strong>Correct!</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_3"> <h2>Measuring energy</h2><p>As discussed already, all of the different manifestations of <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> are related. They all describe a system’s ability to perform some kind of <mark class="term" data-term="work" data-term-def="A process that occurs when a force acts over a distance, as when an object is moved. Work equals the multiple&hellip;" data-term-url="/en/glossary/view/work/1502">work</mark>. As such, they can all be measured using the same <mark class="term" data-term="unit" data-term-def="An accepted quantity used as a standard of measurement. For example, the meter, liter, and gram." data-term-url="/en/glossary/view/unit/848">unit</mark>. Because James Joule was among the first scientists to document the phenomenon of energy conversion, and because his <mark class="term" data-term="observation" data-term-def="1. The act of noticing something. 2. A record of that which has been noticed." data-term-url="/en/glossary/view/observation/8255">observations</mark> were so carefully detailed in his writings, we now call the unit used to measure energy the <mark class="term" data-term="joule" data-term-def="A metric (or SI) unit measuring energy or work and named for the British scientist James Prescott Joule. One joule (J)&hellip;" data-term-url="/en/glossary/view/joule/1503">joule</mark>. This unit formally describes the energy it takes to produce one <mark class="term" data-term="Isaac Newton" data-term-url="/en/glossary/view/Isaac+Newton" data-term-def="English alchemist, physicist, astronomer and mathematician born in Woolsthorpe-by-Colsterworth, Lincolnshire (1643-1727). In 1672, Newton offered an experimental proof that light is&hellip;">newton</mark> of <mark class="term" data-term="force" data-term-def="An influence (a "push or pull") that changes the motion of a moving object (e.g., slows it down, speeds it up,&hellip;" data-term-url="/en/glossary/view/force/883">force</mark> over a distance of one meter or the electrical energy it takes to pass one ampere of <mark class="term" data-term="current" data-term-def="a flow, as of electricity or water. In oceanography and hydrology, a channel of water that flows together at the same velocity" data-term-url="/en/glossary/view/current/8278">current</mark> through a one-ohm resistor for one second.</p><p>While it is important to recognize that we use only one <mark class="term" data-term="unit" data-term-def="An accepted quantity used as a standard of measurement. For example, the meter, liter, and gram." data-term-url="/en/glossary/view/unit/848">unit</mark> to convey the amount of <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> used or given off in a process, it is also important to recognize that we rarely, if ever, can directly measure the energy output itself. Measuring the amount of energy converted in a process is usually done by analyzing changes in other <mark class="term" data-term="parameter" data-term-def="In statistics, a parameter is a numerical value that represents a characteristic of a statistical population. Contrast with statistic." data-term-url="/en/glossary/view/parameter/9481">parameters</mark>, like temperature, and then calculating backwards to <mark class="term" data-term="joule" data-term-def="A metric (or SI) unit measuring energy or work and named for the British scientist James Prescott Joule. One joule (J)&hellip;" data-term-url="/en/glossary/view/joule/1503">joules</mark>.</p><p>For example, if you needed to know how much chemical <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> is stored in a block of wood – and if you don’t have access to tables with that information – there is no tool that we can use to say “that wood contains this much chemical energy.” In order to determine the amount of energy contained in the substance, we must release that energy by burning the block of wood and then measuring the temperature change in the surroundings (this is usually measured using calorimetry, a technique you can read more about in the <a href="/en/library/Physics/24/Thermodynamics-I/200">Thermodynamics I</a> module).</p><p>Without <mark class="term" data-term="experiment" data-term-def="A test or trial carried out under controlled conditions so that specific actions can be performed and the results can be observed." data-term-url="/en/glossary/view/experiment/8292">experiment</mark>, it would not be possible to know the quantity of <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> in an object. As such, measuring energy is perhaps one of the more elusive concepts encountered when we discuss energy. Energy is the potential to do <mark class="term" data-term="work" data-term-def="A process that occurs when a force acts over a distance, as when an object is moved. Work equals the multiple&hellip;" data-term-url="/en/glossary/view/work/1502">work</mark>; however, until it gets used up, we cannot observe how much energy we had!</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc6779"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">To measure chemical energy in a block of wood, it is most common to</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-6779-0-option-a" name="quiz-option-6779" type="radio" value="measure the number of joules and from that number predict the temperature change that will occur when the wood burns." > <span class="option__label"> <span class="screen-reader-only">a.</span> measure the number of joules and from that number predict the temperature change that will occur when the wood burns. </span> </label> <span class="quiz__response" id="response-6779-0"> <strong>Incorrect.</strong> </span> </div> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-6779-1-option-b" name="quiz-option-6779" type="radio" value="measure the temperature change that results from burning the wood and from that number calculate the number of joules." > <span class="option__label"> <span class="screen-reader-only">b.</span> measure the temperature change that results from burning the wood and from that number calculate the number of joules. </span> </label> <span class="quiz__response" id="response-6779-1"> <strong>Correct!</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_4"> <h2>The importance of energy to science</h2><p>From astronomy to zoology, all forms of natural science rely on an understanding of <mark class="term" data-term="energy" data-term-def="An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear, and&hellip;" data-term-url="/en/glossary/view/energy/1497">energy</mark> to some degree. In the physical sciences, our understanding of energy flow helps to predict <mark class="term" data-term="chemical reaction" data-term-def="A process in which atoms and molecules recombine by forming or breaking chemical bonds. Chemical reactions form new products that&hellip;" data-term-url="/en/glossary/view/chemical+reaction/1547">chemical reactions</mark>, determine the trajectory of objects, and many other processes. In the life sciences, energy is used to study how <mark class="term" data-term="enzyme" data-term-def="Molecules produced by living organisms that help catalyze biochemical reactions. Enzymes are predominantly protein or protein-based molecules and are highly&hellip;" data-term-url="/en/glossary/view/enzyme/1595">enzymes</mark> work and why different biomolecules interact in certain ways. Energy is a fundamental concept for all students of science, and it is a cornerstone for existence at large.</p> </div> </section> <hr class="border-color-dark" /> <footer class="module__footer"> <p class="citation"> <em> Anthony Carpi, Ph.D., Zachary Hartman, Ph.D. “Defining Energy” Visionlearning Vol. PHY-1 (6), 2014. </em> </p>  <div class="title-list" id="refs" name="refs"> <p class="h6 title-list__title"> References </p> <ul class="title-list__list"> <li><p>Newton, Isaac. <em>Philosophiae Naturalis Principia Mathematica </em>(“Mathematical Principles of Natural Philosophy”). London, 1687; Cambridge, 1713; London, 1726.</p></li> </ul> </div> </footer> </div>   </div>  <div class="order-1 order-2--lg module__tools"> <div class="narrow margin-x-auto position-sticky-top font-size-md"> <div class="padding-2 border-radius box-shadow-1--lg"> <div class="tabs" role="tablist"> <nav> <button class="button button--icon-label" id="tab-button-in-this-module" aria-label="Table of Contents" aria-controls="tab-panel-module__tools" aria-selected="true" role="tab"> <span class="icon icon-list" aria-hidden="true"></span> <span class="button__text">Contents</span> </button> <button class="button button--icon-label" id="tab-button-toggle-terms" aria-controls="tab-panel-toggle-terms" aria-selected="false" role="tab"> <span class="icon icon-glossary-highlight"></span> <span class="button__text">Glossary Terms</span> </button> </nav> <hr class="divider" /> <div class="tabs__panel shown" id="tab-panel-module__tools" aria-labelledby="tab-button-module__tools" role="tabpanel"> <p class="font-weight-bold margin-bottom-1"> Table of Contents </p> <div class="table-of-contents" id="module-toc"> <ul> <li><a href="/en/library/physics/24/defining-energy/199#toc_1">What is energy?</a> </li> <li> <ul> <li><a href="/en/library/physics/24/defining-energy/199#toc2_1">Mechanical energy</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/physics/24/defining-energy/199#toc2_2">Thermal energy</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/physics/24/defining-energy/199#toc2_3">Chemical energy</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/physics/24/defining-energy/199#toc2_4">Nuclear energy</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/physics/24/defining-energy/199#toc2_5">Electromagnetic energy</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/physics/24/defining-energy/199#toc2_6">Electrical energy</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/physics/24/defining-energy/199#toc2_7">Other forms of energy</a> </li> </ul> </li> <li><a href="/en/library/physics/24/defining-energy/199#toc_2">James Joule and the conversion of energy</a> </li> <li><a href="/en/library/physics/24/defining-energy/199#toc_3">Measuring energy</a> </li> <li><a href="/en/library/physics/24/defining-energy/199#toc_4">The importance of energy to science</a> </li> </ul> </div> </div>   <div class="tabs__panel" id="tab-panel-toggle-terms" aria-labelledby="tab-button-toggle-terms" role="tabpanel"> <div class="reading-toggle"> <div class="reading-toggle__switch"> <div class="form-entry__option__switch"> <label> <input type="checkbox" name="termsToggleSwitch" id="terms-toggle-switch" /> <span class="switch__slider"></span> <span class="option__label text-decoration-none font-size-md"> Highlight Glossary Terms </span> </label> </div> </div> <div class="reading-toggle__help"> <p> <em> Activate glossary term highlighting to easily identify key terms within the module. 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Defining Energy | Physics | Visionlearning