章节大纲

  • Sari and Daniel watch a movie with popcorn, worried about a lightning storm outside.

    Sari and Daniel are spending a stormy Saturday afternoon with cartons of hot popcorn and a spellbinding movie. They are obviously too focused on the movie to wonder where all the comes from to power their weekend entertainment. They’ll give it some thought halfway through the movie when the storm causes the power to go out!
    ::Sari 和 Daniel 周六下午都忙着用热爆米花和一部有魅力的电影。 他们显然太专注这部电影,不知道他们周末的娱乐活动从何而来。 当暴风雨造成权力外泄时,他们会在电影中半途思考。

    Changing Energy
    ::改变能源

    Watching movies, eating hot popcorn, and many other activities depend on electrical energy . Some electrical energy comes from the burning of fossil fuels , which contain stored chemical energy . When fossil fuels are burned, the chemical energy changes to and the thermal energy is then used to generate electrical energy. These are all examples of energy conversion. Energy conversion is the process in which one type of energy changes into another type. When energy changes in this way, the energy isn’t used up or lost. The same amount of energy exists after the conversion as before. Energy conversion obeys the law of conservation of energy , which states that energy cannot be created or destroyed, only transformed.
    ::观看电影,吃热爆米花,以及许多其他活动都依赖于电力能源。一些电力能源来自化石燃料的燃烧,这些燃料含有储存的化学能源。当化石燃料被燃烧时,化学能源的变化和热能随后被用于发电能源。这些都是能源转换的例子。能源转换是一种能源改变成为另一种能源的过程。当能源改变时,能源没有被消耗或消耗。在转换之后,能源的消耗量与以前一样。能源转换符合节能法则,因为法律规定能源是无法创造或摧毁的,只有改变能源。

    How Energy Changes Form
    ::能源变化的形式

    There are many different , including electrical energy, chemical energy, thermal energy, mechanical energy , sound energy , and more. Any of these forms of energy can change into any other form. Often, one form of energy changes into two or more different forms. For example, When you put popcorn kernels in a popcorn , electrical energy is used to up the machine. This electrical energy is transformed into thermal energy, which heats up the kernels and causes them to pop. The popping kernels have mechanical energy, which is the energy of their motion. They also produce sound energy as they pop and bounce around in the machine. You can read more in the Figure how these changes happen.
    ::有很多不同的能源, 包括电能、化学能源、热能、机械能源、声音能源等等。 任何这种能源形式都可以改变为任何其他形式。 通常, 一种形式的能源会改变为两种或两种以上不同的形式。 例如, 在爆米花中放爆米花内核时, 电能会用在机器上。 这种电能会转换成热能, 热能会让内核升温, 并导致它们爆出。 弹出内核有机械能源, 也就是运动的能量。 当机器中弹出和弹出时, 它们也会产生声音能量。 您可以在图表中看到这些变化是如何发生的。

    Popcorn machine showing popcorn popping, illustrating energy conversion from electrical to mechanical and sound energy.
    1. The popcorn machine changes electrical to thermal energy, which heats the popcorn. 2. The heat causes the popcorn to pop. You can see that the popping corn has mechanical energy (energy of movement). It overflows the pot and falls into the pile of popcorn at the bottom of the machine. 3. The popping corn also has energy. That's why it makes popping sounds.

    Kinetic-Potential Energy Changes
    ::动力动力能量变化

    Mechanical energy commonly changes between kinetic and . is the energy of moving objects. Potential energy is energy that is stored in objects, typically because of their position or shape. Kinetic energy can be used to change the position or shape of an object, giving it potential energy. Potential energy gives the object the potential to move. If it does, the potential energy changes back to kinetic energy.
    ::移动物体的能量是动能和.移动物体的能量。潜在的能量是存储在物体中的能量,通常是由于其位置或形状。动能可以用来改变物体的位置或形状,并赋予它潜在的能量。潜在的能量使物体具有移动的潜力。如果它这样做,潜在的能量会回到动能。

    That’s what happened to Sari. After she and Daniel left the theater, the storm cleared and they went for a swim. That’s Sari in the Figure coming down the water slide. When she was at the top of the slide, she had potential energy. Why? She had the potential to slide into the water because of the pull of gravity. As she moved down the slide, her potential energy changed to kinetic energy. By the time she reached the water, all the potential energy had changed to kinetic energy.
    ::Sari就是这样。 在她和Daniel离开剧院后,暴风雨一扫而空,他们就去游泳了。图中的Sari从水流滑下来。当她站在幻灯片的顶端时,她就有了潜在的能量。 为什么?她有潜力因为引力的拉动而滑入水中。 当她下坡时,她的潜在能量变成了动能。 当她到达水面时,所有潜在的能量都变成了动能。

    A child joyfully sliding down a water slide into a splash of water.

    Q: How could Sari regain her potential energy?
    ::问题:Sari如何恢复其潜在能量?

    A: Sari could climb up the steps to the top of the slide. It takes kinetic energy to climb the steps, and this energy would be stored in Sari as she climbed. By the time she got to the top of the slide, she would have the same amount of potential energy as before.
    ::A:莎莉可以攀登到幻灯片顶端的阶梯。它需要动能才能攀登台阶,而这种能量将在她攀登时储存在莎里。 当她到达幻灯片顶端时,她将拥有与以前相同的潜在能量。

    Q: Can you think of other fun examples of energy changing between kinetic and potential energy?
    ::问:你能想到其他有趣的例子吗?

    A: Playground equipment such as swings, slides, and trampolines involve these changes.
    ::A: 摇摆、幻灯片和蹦床等游乐场设备涉及这些变化。

     

     

    Summary
    ::摘要

    • Energy conversion is the process in which energy changes from one form or type to another. Energy is always conserved in energy conversions.
      ::能源转换是能源从一种形式或类型变化到另一种形式或类型的过程。 能源转换总是在能源转换中节能。
    • Different forms of energy—such as electrical, chemical, and thermal energy—often change to other forms of energy.
      ::不同形式的能源——例如电力、化学和热能——往往改变为其他形式的能源。
    • Mechanical energy commonly changes back and forth between kinetic and potential energy.
      ::机械能源通常在动能和潜在能源之间前后变化。

    Review
    ::回顾

    1. Define energy conversion.
      ::界定能源转换。
    2. Relate energy conversion to the law of conservation of energy.
      ::将能源转换与节能法联系起来。
    3. Describe an original example of energy changing from one form to two other forms.
      ::描述能源从一种形态变化为另一种形态的原始例子。
    4. Explain how energy changes back and forth between kinetic and potential energy when you jump on a trampoline. Include a sketch to help explain the energy conversions.
      ::解释一下当你跳上踏板时, 动能和潜在能量之间的能量变化。 包括一个帮助解释能量转换的草图 。