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Q what is energy and how can it change its form?*Energy comes in many forms:
Energy: the capacity to do work or transfer heat.
Moving energy(kinetic energy): Moving matter has kinetic energy because of its mass and its velocity. Exp: heat & electromagnetic radiation.
Stored energy(potential energy): Which is stored and potentially available for use.
Potential energy can be changed to kinetic energy.
* Some type of energy are more useful than others:
Energy quality: a measure of an energy source's capacity to do useful work
High-quality energy: concentrated and can perform much useful work.
Low-quality energy: is dispersed and has little capacity to do useful work.
*Energy change are governed by two scientific laws:
First law of thermodynamics: When energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed.
Second law of thermodynamics: When energy changes from oneform to another, we always end up with lower quality or less usable energy than we started with.
energy always goes from a more useful to a less useful form when it change from one form to another.
Energy efficiency(energy productivity): a measure of how much useful work is accomplished by a particular input of energy into a system.
能量來自很多種形式，而能量大致上可分為動能和位能，動能是物體因運動而產生的能量，而位能可能是動能轉換來的或本身就有的能量。電磁波是另一種形式的能量，是以能量波的形式來改變磁場與電場。熱學的第一定律能量守恆，說明能量不會無端的消失或生成，而熱學的第二定律，說明能量在轉換時，無法完全轉換而使其中有些能量消失。