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20_Energy.html
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<p class="head">Energy</p>
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<p>In physics, <a class="def">energy</a> is the capacity for doing work. Energy is in everything – in heat, light, chemical bonds, compressed springs, falling objects and a number of other places. Every time when something gets warm, cools down, moves, grows, makes a sound or changes in any way, it uses energy. A pen sitting on a desk and not moving still has energy – it is just not using it.</p>
<p>Energy comes in many forms, such as heat, sound, light, electric, chemical, nuclear, mechanical, gravitational. The total amount of energy in the universe has always been and will always be constant. However, energy can change from one form to another and transfer between objects. So, <a class="def">energy cannot be created or destroyed, but it can be transformed and transferred</a>.</p>
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<div class="desc">Diagram showing how different forms of energy can be converted to another form of energy. © <a href="https://www.solarschools.net/knowledge-bank/energy/conversion" target="_blank">https://www.solarschools.net</a>
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<p>There are many examples of <a class="def">energy transformation (or conversion)</a> around us. When we talk on the telephone, the sound we produce is first transformed into electrical energy by the microphone that is transmitted along wires. In the case of cellular phones, the sound is converted into electromagnetic waves and transmitted through the air. The speaker of the phone on the other end changes the electromagnetic waves energy back into sound energy. When we eat a sandwich, chemical energy stored in the sandwich is converted into mechanical energy of our moving body. </p>
<p>When a billiard ball rolls on the table and hits another ball, it transfers some of its kinetic energy to it, so that the second ball is also turned to move. This is an example of <a class="def">energy transfer</a> from one ball to another.</p>
<p>Despite the fact that numerous forms of energy exist, they all fall into two categories: kinetic and potential energy. <a class="def">Kinetic energy</a> is the energy an object has due to its motion. <a class="def">Potential energy</a> is the energy stored in an object.</p>
<p>A ball sitting at the top of a hill has potential energy. When a force pushes it down the hill, that potential energy transforms into kinetic energy of the ball. The ball continues losing potential energy and gaining kinetic energy until it reaches the bottom of the hill [<a class="ref" href=bibliography.html#nationalgeo>nationalgeo</a>]. In this example, there is a transformation of the potential energy to kinetic energy.</p>
<p class="acknow">Acknowledgements: [<a class="ref" href=bibliography.html#nationalgeo>nationalgeo</a>], [<a class="ref" href=bibliography.html#wikieducator>wikieducator</a>], [<a class="ref" href=bibliography.html#solarschools>solarschools</a>].</p>
<p class="important">More on the subject: <a href="https://www.youtube.com/watch?v=DvCWuOuaG_c" target="_blank">https://www.youtube.com</a>, <a href="https://wikieducator.org/Lesson_1:_Forms_of_Energy_and_Energy_Transformations#:~:text=In%20this%20lesson%2C%20we%20are,the%20other%2C%20usually%20with%20losses" target="_blank">https://wikieducator.org</a>, <a href="https://www.solarschools.net/knowledge-bank/energy/types" target="_blank">www.solarschools.net</a>.</p>
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