全国职称外语等级考试综合类概括大意九
<p> <span word="PASSAGE">PASSAGE</span> 18</p><p> <span word="Volts">Volts</span> <span word="from">from</span> <span word="the">the</span> <span word="Sky">Sky</span></p><p> <span word="Lightning">Lightning</span> <span word="has">has</span> <span word="caused">caused</span> <span word="awe">awe</span> <span word="and">and</span> <span word="wonder">wonder</span> <span word="since">since</span> <span word="old">old</span> <span word="times">times</span>. <span word="Although">Although</span> <span word="Benjamin">Benjamin</span> <span word="Franklin">Franklin</span> <span word="demonstrated">demonstrated</span> <span word="lightning">lightning</span> <span word="as">as</span> <span word="enormous">enormous</span> <span word="electrical">electrical</span> <span word="discharge">discharge</span> <span word="more">more</span> <span word="than">than</span> 200 <span word="years">years</span> <span word="ago">ago</span>， <span word="many">many</span> <span word="puzzles">puzzles</span> <span word="still">still</span> <span word="surround">surround</span> <span word="this">this</span> <span word="powerful">powerful</span> <span word="phenomenon">phenomenon</span>.</p><p> <span word="Lightning">Lightning</span> <span word="is">is</span> <span word="generated">generated</span> <span word="when">when</span> <span word="electrical">electrical</span> <span word="charges">charges</span> <span word="separate">separate</span> <span word="in">in</span> <span word="rain">rain</span> <span word="clouds">clouds</span>， <span word="though">though</span> <span word="processes">processes</span> <span word="are">are</span> <span word="still">still</span> <span word="not">not</span> <span word="fully">fully</span> <span word="understood">understood</span>. <span word="Typically">Typically</span>， <span word="positive">positive</span> <span word="charges">charges</span> <span word="build">build</span> <span word="at">at</span> <span word="the">the</span> <span word="cloud">cloud</span> <span word="top">top</span>， <span word="while">while</span> <span word="the">the</span> <span word="bottom">bottom</span> <span word="becomes">becomes</span> <span word="negatively">negatively</span> <span word="charged">charged</span>. <span word="In">In</span> <span word="most">most</span> <span word="instances">instances</span> <span word="of">of</span> <span word="cloud">cloud</span>-<span word="to">to</span>-<span word="ground">ground</span> <span word="lightning">lightning</span>， <span word="the">the</span> <span word="negatively">negatively</span> <span word="charged">charged</span> <span word="lower">lower</span> <span word="portion">portion</span> <span word="of">of</span> <span word="the">the</span> <span word="cloud">cloud</span> <span word="repels">repels</span> <span word="negatively">negatively</span> <span word="charged">charged</span> <span word="particles">particles</span> <span word="on">on</span> <span word="the">the</span> <span word="ground">ground</span> <span word="s">s</span> <span word="surfaces">surfaces</span>， <span word="making">making</span> <span word="it">it</span> <span word="become">become</span> <span word="positively">positively</span> <span word="charged">charged</span>. <span word="The">The</span> <span word="positive">positive</span> <span word="charge">charge</span> <span word="on">on</span> <span word="the">the</span> <span word="ground">ground</span> <span word="gathers">gathers</span> <span word="at">at</span> <span word="elevated">elevated</span> <span word="points">points</span>.</p><p> <span word="A">A</span> <span word="flow">flow</span> <span word="of">of</span> <span word="electrons">electrons</span> <span word="begins">begins</span> <span word="between">between</span> <span word="the">the</span> <span word="cloud">cloud</span> <span word="and">and</span> <span word="earth">earth</span>. <span word="When">When</span> <span word="the">the</span> <span word="voltage">voltage</span> <span word="charge">charge</span> <span word="becomes">becomes</span> <span word="large">large</span> <span word="enough">enough</span>， <span word="it">it</span> <span word="breaks">breaks</span> <span word="through">through</span> <span word="the">the</span> <span word="insulating">insulating</span> <span word="barrier">barrier</span> <span word="of">of</span> <span word="air">air</span>， <span word="and">and</span> <span word="electrons">electrons</span> <span word="zigzag">zigzag</span> <span word="earthward">earthward</span>. <span word="We">We</span> <span word="see">see</span> <span word="the">the</span> <span word="discharge">discharge</span> <span word="as">as</span> <span word="lightning">lightning</span>.</p><p> <span word="Lightning">Lightning</span> <span word="can">can</span> <span word="occur">occur</span> <span word="within">within</span> <span word="a">a</span> <span word="cloud">cloud</span>， <span word="between">between</span> <span word="clouds">clouds</span>， <span word="or">or</span> <span word="between">between</span> <span word="clouds">clouds</span> <span word="and">and</span> <span word="the">the</span> <span word="ground">ground</span>. <span word="The">The</span> <span word="first">first</span> <span word="variety">variety</span>， <span word="intra">intra</span>-<span word="cloud">cloud</span> <span word="lightning">lightning</span>， <span word="is">is</span> <span word="the">the</span> <span word="most">most</span> <span word="frequent">frequent</span> <span word="but">but</span> <span word="is">is</span> <span word="often">often</span> <span word="hidden">hidden</span> <span word="from">from</span> <span word="our">our</span> <span word="view">view</span>. <span word="Cloud">Cloud</span>-<span word="to">to</span>-<span word="ground">ground</span> <span word="lightning">lightning</span>， <span word="making">making</span> <span word="up">up</span> <span word="about">about</span> 20 <span word="percent">percent</span> <span word="of">of</span> <span word="lightning">lightning</span> <span word="discharges">discharges</span>， <span word="is">is</span> <span word="what">what</span> <span word="we">we</span> <span word="usually">usually</span> <span word="see">see</span>. <span word="Lightning">Lightning</span> <span word="comes">comes</span> <span word="in">in</span> <span word="several">several</span> <span word="forms">forms</span>， <span word="including">including</span> <span word="sheet">sheet</span>， <span word="ribbon">ribbon</span>， <span word="and">and</span> <span word="ball">ball</span>. <span word="Intra">Intra</span>-<span word="cloud">cloud</span> <span word="lightning">lightning</span> <span word="can">can</span> <span word="illuminate">illuminate</span> <span word="a">a</span> <span word="cloud">cloud</span> <span word="so">so</span> <span word="it">it</span> <span word="looks">looks</span> <span word="like">like</span> <span word="a">a</span> <span word="white">white</span> <span word="sheet">sheet</span>， <span word="hence">hence</span> <span word="its">its</span> <span word="name">name</span>. <span word="When">When</span> <span word="cloud">cloud</span>-<span word="to">to</span>-<span word="ground">ground</span> <span word="lightning">lightning</span> <span word="occurs">occurs</span> <span word="during">during</span> <span word="strong">strong</span> <span word="winds">winds</span>， <span word="they">they</span> <span word="can">can</span> <span word="shift">shift</span> <span word="the">the</span> <span word="lightning">lightning</span> <span word="channel">channel</span> <span word="sideways">sideways</span>， <span word="so">so</span> <span word="it">it</span> <span word="looks">looks</span> <span word="like">like</span> <span word="a">a</span> <span word="ribbon">ribbon</span>. <span word="The">The</span> <span word="average">average</span> <span word="lightning">lightning</span> <span word="strike">strike</span> <span word="is">is</span> <span word="more">more</span> <span word="than">than</span> 3 <span word="miles">miles</span> <span word="long">long</span> <span word="and">and</span> <span word="can">can</span> <span word="travel">travel</span> <span word="at">at</span> <span word="a">a</span> <span word="tenth">tenth</span> <span word="of">of</span> <span word="the">the</span> <span word="speed">speed</span> <span word="of">of</span> <span word="light">light</span>. <span word="Ball">Ball</span> <span word="lightning">lightning</span>， <span word="the">the</span> <span word="rarest">rarest</span> <span word="and">and</span> <span word="most">most</span> <span word="mysterious">mysterious</span> <span word="form">form</span>， <span word="derives">derives</span> <span word="its">its</span> <span word="name">name</span> <span word="from">from</span> <span word="the">the</span> <span word="small">small</span> <span word="luminous">luminous</span> <span word="ball">ball</span> <span word="that">that</span> <span word="appears">appears</span> <span word="near">near</span> <span word="the">the</span> <span word="impact">impact</span> <span word="point">point</span>， <span word="moves">moves</span> <span word="horizontally">horizontally</span>， <span word="and">and</span> <span word="lasts">lasts</span> <span word="for">for</span> <span word="several">several</span> <span word="seconds">seconds</span>.</p>
页:
[1]