<div>2b-unit10 There is thunder 拓展 part2<br></div>今日主题----闪电。有了昨天静电部分的铺垫，了解到身边的静电想象，那么移植到天空中云朵带电，理解起来就容易一些。<div><br><div><b>1. What is lightning?</b><br>Lightning is a bright flash of electricity produced by a thunderstorm. All thunderstorms produce lightning and are very dangerous. If you hear the sound of thunder, then you are in danger from lightning. Lightning kills and injures more people each year than hurricanes or tornadoes; between 75 to 100 people.<br></div></div> <b>2. What causes lightning?</b><br><ul><li>Lightning is an electric current. 闪电是电流。</li><li>Within a thundercloud way up in the sky, many small bits of ice (frozen raindrops) bump into each other as they move around in the air. All of those collisions create an electric charge. After a while, the whole cloud fills up with electrical charges. The positive charges or protons form at the top of the cloud and the negative charges or electrons form at the bottom of the cloud.在空中的雷云中，许多小块冰（冻雨滴）在空中移动时会相互碰撞。所有这些碰撞都会产生电荷。 一段时间后，整个云充满了电荷。 正电荷或质子形成在云层的顶部，负电荷或电子形成在云层的底部。</li><li> Since opposites attract, that causes a positive charge to build up on the ground beneath the cloud. The grounds electrical charge concentrates around anything that sticks up, such as mountains, people, or single trees. The charge coming up from these points eventually connects with a charge reaching down from the clouds and - zap - lightning strikes!由于相反的事物吸引，因此会在云层下方的地面上积聚正电荷。地面上的电荷集中在粘附的任何物体上，例如山脉，人或单树。 从这些点上来的电荷最终与从云层上下来的电荷相连，并且-击打-雷击！ </li></ul> Have you ever rubbed your feet across carpet and then touched a metal door handle? If so, then you know that you can get shocked! Lightning works in the same way. <b>3. Types of lightning and types of lighting strikes</b> There are three primary types of lightning:<br><b>Intracloud (IC)</b><br> Occurs within a single thundercloud<br> In intracloud lightning, the reaction occurs between areas of differing electrical potential<br> Most frequently occurring type of lightning<br> Commonly occurs between the upper and lower levels of a thunderstorm<br><b>Cloud to Cloud (CC)</b><br> Starts and ends between two different thunderclouds<br> Another term for cloud-to-cloud lightning is 'Anvil Crawler' for its scrambling motion through cloud layers of a thunderstorm<br> This can also be referred to as 'Spider lightning'<br> Usually seen as a thunderstorm, passes over the observer or when the storm is settling down<br><b>Cloud to ground (CG)</b><br> Begins in a thundercloud and ends on the ground<br> Least common type of lightning<br> Best understood type of lightning<br> Easily measurable by instruments due to it ending on a physical object (Earth)<br> Poses the greatest threat to life and property since it strikes the Earth<br> Can be positive or negative (positive is more dangerous)<div><b><br></b></div><div><b>Ball lightning 球形闪电</b><br></div> Ball lightning is a glowing ball of lightning that sometimes appears in a thunderstorm, but usually lasts much longer than lightning. Scientists do not understand ball lightning very well, and some even do not think ball lightning is real, because it is so strange. However, it has been widely reported in weather journals by many trustworthy people. So, it is very possible that it is real.<br> <div>讨论闪电形成的原理，一起制作手工，利用剃须泡沫当做云朵，毛根做闪电，看起来还不错。</div> <b>4. Types of lightning strikes</b> <b>5. Experiment </b><br><b>Wimshurst generatorWimshurst静电发生器</b><br>The Wimshurst electrostatic generator was invented in the 1880s. The modern version consists of two plastic discs that are rotated in opposite directions by a hand-crank and drive belt mechanism. Wimshurst静电发生器是在1880年代发明的。 现代版本包括两个塑料盘，它们通过手摇曲柄和传动带机构沿相反的方向旋转。 <ul></ul><p></p><p>很早之前就买了这个静电发生器，对如何发电和放电Eric已经有了一些了解。</p><p><b>Parts of Wimshurst generator</b></p> <ul><li><b>How it works</b></li></ul>The way it works is that a number of metal foil sectors are cemented onto two discs. As the discs turn, each metal foil sector accumulates the charges through contact with brushes on bars near the front and back of the discs. Two additional pairs of brushes collect the accumulated charges and transmit them to the storage capacitor, such as a Leyden jar.<br>它的工作方式是将许多金属箔扇区粘合到两个圆盘上。 随着光盘旋转，每个金属箔扇形都通过与光盘前后面板附近的刷子接触而积累电荷。 另外两对电刷收集累积的电荷并将其传输到存储电容器（例如莱顿瓶）<br><br>The brushes also are connected to spark gap electrodes. As the discs revolve, a high voltage spark can jump between the electrodes if they are gradually brought together. 电刷也连接到火花隙电极。 随着圆盘旋转，如果逐渐将它们聚集在一起，则高压火花会在电极之间跳跃。<br><div><br></div><div><b>Generates 75,000 volts</b><br>The Wimshurst electrostatic generator can generate up to 75,000 volts. Since the current is very low, there is little danger from the high voltage, but yet it is effective for creating sparks and performing interesting static electricity experiments. Wimshurst静电发生器可以产生高达75,000伏的电压。 由于电流非常低，因此高电压几乎没有危险，但是它对于产生火花和进行有趣的静电实验非常有效。<br></div> 尝试讲解静电发生器的工作原理，在实验的过程中居然还闻到了臭氧的味道，分析了高压放电对空气产生的电离，所以产生了臭氧，Eric立马联想到泡脚盆的臭氧。