TPO是我們常用的托福?？脊ぞ?，對我們的備考很有價值，下面小編給大家?guī)硗懈ｉ喿xTPO18(試題+答案+譯文)第3篇:Lightning。

托福閱讀原文

【1】Lightning is a brilliant flash of light produced by an electrical discharge from a storm cloud. The electrical discharge takes place when the attractive tension between a region of negatively charged particles and a region of positively charged particles becomes so great that the charged particles suddenly rush together. The coming together of the oppositely charged particles neutralizes the electrical tension and releases a tremendous amount of energy, which we see as lightning. The separation of positively and negatively charged particles takes place during the development of the storm cloud.

【2】The separation of charged particles that forms in a storm cloud has a sandwich-like structure. Concentrations of positively charged particles develop at the top and bottom of the cloud, but the middle region becomes negatively charged. Recent measurements made in the field together with laboratory simulations offer a promising explanation of how this structure of charged particles forms. What happens is that small (millimeter-to centimeter-size) pellets of ice form in the cold upper regions of the cloud. When these ice pellets fall, some of them strike much smaller ice crystals in the center of the cloud. The temperature at the center of the cloud is about -15℃ or lower. At such temperatures, the collision between the ice pellets and the ice crystals causes electrical charges to shift so that the ice pellets acquire a negative charge and the ice crystals become positively charged. Then updraft wind currents carry the light, positively charged ice crystals up to the top of the cloud. The heavier negatively charged ice pellets are left to concentrate in the center. This process explains why the top of the cloud becomes positively charged, while the center becomes negatively charged. The negatively charged region is large: several hundred meters thick and several kilometers in diameter. Below this large, cold, negatively charged region, the cloud is warmer than -15℃, and at these temperatures, collisions between ice crystals and falling ice pellets produce positively charged ice pellets that then populate a small region at the base of the cloud.

【3】Most lightning takes place within a cloud when the charge separation within the cloud collapses. However, as the storm cloud develops, the ground beneath the cloud becomes positively charged and lightning can take place in the form of an electrical discharge between the negative charge of the cloud and the positively charged ground. Lightning that strikes the ground is the most likely to be destructive, so even though it represents only 20 percent of all lightning, it has received a lot of scientific attention.

【4】Using high-speed photography, scientists have determined that there are two steps to the occurrence of lightning from a cloud to the ground. First, a channel, or path, is formed that connects the cloud and the ground. Then a strong current of electrons follows that path from the cloud to the ground, and it is that current that illuminates the channel as the lightning we see.

【5】The formation of the channel is initiated when electrons surge from the cloud base toward the ground. When a stream of these negatively charged electrons comes within 100 meters of the ground it is met by a stream of positively charged particles that comes up from the ground. When the negatively and positively charged streams meet, a complete channel connecting the cloud and the ground is formed. The channel is only a few centimeters in diameter, but that is wide enough for electrons to follow the channel to the ground in the visible form of a flash of lightning. The stream of positive particles that meets the surge of electrons from the cloud often arises from a tall pointed structure such as a metal flagpole or a tower. That is why the subsequent lightning that follows the completed channel often strikes a tall structure.

【6】Once a channel has been formed, it is usually used by several lightning discharges, each of them consisting of a stream of electrons from the cloud meeting a stream of positive particles along the established path. Sometimes, however, a stream of electrons following an established channel is met by a positive stream making a new path up from the ground. The result is a forked lightning that strikes the ground in two places.

托福閱讀試題

1.According to paragraph 1, all of the following take place in the development of a flash of lightening EXCEPT

A.great tension between two oppositely charged regions.

B.an increase in negatively charged particles over positively charged particles.

C.oppositely charged particles coming together.

D.the release of electrical energy in the form of visible light.

2.The word “tremendous” in passage 1 is closest in meaning to

A.distinct.

B.growing.

C.huge.

D.immediate.

3.According to paragraph 2, what causes ice crystal to become positively charged?

A.Collisions with ice pellets.

B.Collisions with negatively charged ice crystals at the base of the cloud.

C.Becoming concentrated in the central region of the cloud.

D.Forming at a temperature greater than -15℃.

4.The word “acquire” in passage 2 is closest in meaning to

A.reject.

B.obtain.

C.need.

D.produce.

5.According to paragraph 2, why are positively charged ice pellets produced in the lower part of the cloud?

A.Collisions between ice crystals and ice pellets increase in number in the lower part of the cloud.

B.The lower part of the cloud is smaller than the region above it.

C.More ice pellets than ice crystals reach the lower part of the cloud.

D.Temperature in the lower part of the cloud are warmer than -15℃.

6.According to paragraph 2, the middle region of a cloud becomes negatively charged due to all of the following EXCEPT

A.a shift of electrical charged between ice pellets and ice crystals.

B.negatively charged ice pellets that remain in the middle.

C.a temperature of -15℃ or less.

D.the development of a positive charge at the base of the cloud.

7.It can be inferred from paragraph 2 that part of the reason that the top of a storm cloud becomes positively charged is that

A.the top of the cloud is warmer than the middle of the cloud.

B.the middle of the cloud is already occupied by positively charged particles.

C.the negatively charged ice pellets are too heavy to be carried by the updrafts that move ice crystals.

D.collisions between ice pellets in the top of the cloud produce mainly positively charged particles.

8.The author remarks that (in paragraph 3)“Lightning that strikes the ground is the most likely to be destructive” in order to explain why

A.this form of lightning has been investigated so much.

B.this form of lightning is not as common as lightning within a cloud.

C.scientific understanding of this form of lightning is important.

D.the buildup of positive charge on the ground beneath a storm cloud can have serious consequences.

9.The word “illuminates” in passage 4 is closet in meaning to

A.opens.

B.completes.

C.lights.

D.electrifies.

10.According to paragraph5, which of the following is true of the stream of charged particles from the ground?

A.It prevents streams of electrons from the cloud from striking the ground.

B.It completes a channel that connects the storm cloud with the ground.

C.It produces a stream of electrons from the cloud.

D.It widens the path made by the initial stream of electrons from the cloud.

11.Which of the following claims about lightning strikes can be inferred from paragraph 5?

A.During a lightning strike the diameter of the channel the electrons follow is considerably enlarged beyond a few centimeters.

B.A building is unlikely to be hit by lightning unless it is at least 100 meters tall.

C.A building is hit by a lightning strike because the building itself has first determined the path the lightening then takes to it.

D.The light of a lightning strike first appears at the point where the streams of negative and positive particles meet.

12.The word “initiated”in paragraph 5 is closet in meaning to

A.started.

B.intensified.

C.finished.

D.expected.

13. Look at the four squares [■] that indicate where the following sentence could be added to the passage. Where would the sentence best fit? The descending stream of electrons divides at the point where the new positive-stream channel intersects the established path.

The formation of the channel is initiated when electrons surge from the cloud base toward the ground. When a stream of these negatively charged electrons comes within 100 meters of the ground it is met by a stream of positively charged particles that comes up from the ground. When the negatively and positively charged streams meet, a complete channel connecting the cloud and the ground is formed. The channel is only a few centimeters in diameter, but that is wide enough for electrons to follow the channel to the ground in the visible form of a flash of lightning. The stream of positive particles that meets the surge of electrons from the cloud often arises from a tall pointed structure such as a metal flagpole or a tower. That is why the subsequent lightning that follows the completed channel often strikes a tall structure. ■【A】

Once a channel has been formed, it is usually used by several lightning discharges, each of them consisting of a stream of electrons from the cloud meeting a stream of positive particles along the established path. ■【B】 Sometimes, however, a stream of electrons following an established channel is met by a positive stream making a new path up from the ground. ■【C】 The result is a forked lightning that strikes the ground in two places. ■【D】

14. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THERR answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

Lightning takes place when a separation of a positive and negative electrical particles that develops in a storm could suddenly collapses.

A.A storm cloud first develops a positively charged layer at the top, then a negatively charged middle layer, and finally, a positively charged layer at the bottom.

B.A separation of oppositely charged particles in clouds develops from collisions of falling ice pellets with ice crystals, from updrafts, and from temperature variations.

C.Lightning from cloud to ground follows a channel that forms when a stream of electrons moving down meets a stream of positive particles coming up from the ground.

D.Field studies, laboratory simulations, and high-speed photography have all been used to investigate the way charge separations develop in clouds.

E.Lightning from a cloud to the ground is more likely to be destructive than is lightning that takes place within a cloud.

F.Once a channel has been formed, it is usually used by several successive electrical discharges that illuminate the channel as flashes of lightning.

托福閱讀答案

1.EXCEPT題，排除法，A的tension和做關(guān)鍵詞定位至第二句，正確，不選;B的negatively和positively charged particles同樣定位至第二句，但原文沒有比較，所以B沒說，選;C的come together和D的release做關(guān)鍵詞定位都至倒數(shù)第二句，都正確，都不選。

2.tremendous大量的，巨大的，所以正確答案是huge。原句說當(dāng)帶相反電荷的例子碰到一起的時候發(fā)生中和并釋放什么樣的能量，就是我們能看到的閃電，大家都知道閃電的能量很大，所以選huge，C。A不同B增大D立刻都不靠譜。

3.以ice crystal和positively charged做關(guān)鍵詞定位至第七句，說在這樣的溫度下，ice pellet和ice crystal的碰撞轉(zhuǎn)移了電荷，使得pellet帶負(fù)電，crystal帶正電，所以答案應(yīng)該是A碰撞;B雖然也說到碰撞，但不是和負(fù)電碰撞;D的溫度不是帶正電的決定條件。

4.acquire獲得，所以答案obtain正確，正如上題，原句說ice pellet和ice crystal的碰撞轉(zhuǎn)移了電荷，使得pellet怎么樣負(fù)電，crystal帶正電，至少猜出acquire應(yīng)該和become差不多，是個從無到有的過程，答案是B。需要不一定有，C錯;A拒絕與原文相反;D錯，電荷不能產(chǎn)生。

5.以positively charged ice pellets做關(guān)鍵詞定位至最后一句，說在這個很大的，帶負(fù)電的區(qū)域之下，碰撞 產(chǎn)生了positively charged pellets，所以答案是D。A的increase in number，B的smaller和C的比較原文都沒說。

6.EXCEPT題，排除法，A的ice pellets and ice crystals做關(guān)鍵詞定位至第七句，正確，不選;B的in the middle做關(guān)鍵詞定位至倒數(shù)第四句，正確，不選;C的數(shù)字做關(guān)鍵詞定位至第六句，正確，不選;D的the base of the cloud做關(guān)鍵詞定位都至最后一句，但倒數(shù)第三句已經(jīng)說過this process explains，也就是說原因到倒數(shù)第三句就給完了，D不是原因，錯，選。

7.修辭目的題，修辭點(diǎn)所在句子說這種閃電具有破壞性，所以盡管這類閃電只占全部的20%，它仍然受到了很多關(guān)注，也就是解釋下受關(guān)注是因?yàn)榫哂衅茐男?，所以答案是A。

8.illuminate發(fā)光，照射，所以C的light是正確答案。原句說一股強(qiáng)烈的電子流沿通路從云層到地面，并且怎么樣了那個通路，成為我們所看到的閃電，如果不照亮怎么看到閃電呢?所以C正確;A打開B完成D使帶電都不能解釋看見，所以都不對。

9.以stream of charged particles from the ground做關(guān)鍵詞定位至第二句，說來自地面的帶負(fù)電的電子流會在地面以上100米左右碰上來自云層的帶正電的電子流，然后又說當(dāng)二者碰在一起的時候就形成了通路，所以B形成通路是正確的。A的prevent，C的produce和D的widen原文都沒說。

10.因此題關(guān)鍵詞比較難找，所以用排除法。A的diameter of the channel和centimeter做關(guān)鍵詞定位至第四句，但原文沒有信息能推出widen，所以A錯;B的數(shù)字做關(guān)鍵詞定位至第二句，說100米內(nèi)正負(fù)電荷就會碰到，所以B說反;C的path做關(guān)鍵詞定位至最后一句的channel，說正電荷通常升起自地面上的一個高點(diǎn)，比如旗桿，然后閃電由通路到達(dá)地面，也就是說旗桿等高的建筑物是這個channel的一部分，所以C說building決定了path是對的，選C;D的first appear原文沒有相關(guān)信息。

11.以top of the storm cloud做關(guān)鍵詞定位至倒數(shù)第五句，說向上的氣流將輕的，帶正電的粒子帶到云層上部，這自然是上部云層帶正電的原因，反過來說也就是帶負(fù)電的粒子很重，所以沒有上來，所以答案是C。原文只是說了中部和下部的溫度，上部溫度沒有信息，所以A錯;由倒數(shù)第四句可知中部是負(fù)電，B說反了;D原文也沒說。

12.initiate開始，所以正確答案是A。原文說通路形成怎么了，當(dāng)云層底部的電子向地面運(yùn)動的時候，接著又說這些云層中的粒子和地面上來的粒子碰到一起之后，閃電的通路就完全形成了，也就是上文的云層底部的電子下來是形成的開始，所以答案是start，C結(jié)束說反了;B加強(qiáng)和D期望完全不靠譜。

13.兩個過渡點(diǎn)，名詞established path和動詞divide，根據(jù)established path可以確定答案是A/B/C，注意原文中established channel和established path是同義詞，所以不要忘了C答案，根據(jù)divide與最后一句forked的同義替換確定C或者D，所以C是答案。

14.A storm選項(xiàng)明顯不對，因?yàn)檎?fù)電荷是同時形成的，沒有先后，A不選。Lightning from cloud to ground選項(xiàng)對應(yīng)原文第五段的第一句和第三句，C正確。Lightning from a cloud to the ground選項(xiàng)MS對應(yīng)第三段最后一句，但原文沒有比較，E不選。A separation選項(xiàng)對應(yīng)原文第二段，B正確。Field選項(xiàng)是原文第二段和第四段的細(xì)節(jié)，D不選。Once選項(xiàng)對應(yīng)原文最后一段第一句，F(xiàn)正確。

托福閱讀譯文

【1】閃電是由雷雨云放電產(chǎn)生的一道明亮奪目的閃光。當(dāng)帶正電荷粒子區(qū)域與帶負(fù)電荷粒子區(qū)域之間的吸引力大到使帶電粒子瞬間碰撞到一起就會發(fā)生放電現(xiàn)象。相反的帶電粒子的結(jié)合中和了電壓并釋放出巨大的能量，這就是我們看到的閃電。在雷雨云形成的過程中正負(fù)帶電粒子相互分離。

【2】形成雷雨云的帶電粒子的分離具有一種三明治結(jié)構(gòu)。帶正電的粒子聚集在云的頂部和底部，但是中間區(qū)域形成的是帶負(fù)電的粒子。近期的野外測量以及實(shí)驗(yàn)室模擬為這種帶電粒子的排列結(jié)構(gòu)提供了可能的解釋。實(shí)際上在此過程中在云層較冷的上部區(qū)域形成了細(xì)小的(毫米到厘米大小)冰丸。當(dāng)這些冰丸飄落時，一部分會與云層中心比冰丸小得多的冰晶相撞。云層中心的溫度大約在零下15攝氏度或者更低。在此溫度下，冰丸和冰晶的撞擊會使電荷發(fā)生轉(zhuǎn)移，冰丸由此獲得了負(fù)電而冰晶獲得了正電。隨后上升氣流會將較輕的正電冰晶帶到云的頂部。較重的負(fù)電冰丸會留在云層中部并積累起來。這個過程解釋了為什么云的頂部帶正電而中部帶負(fù)電。帶負(fù)電的區(qū)域非常大：厚度達(dá)數(shù)百米，直徑達(dá)幾千米。位于這片又大又冷的帶負(fù)電區(qū)域之下的云層的溫度要高于零下15攝氏度，在此溫度下，冰晶和降落的冰丸的碰撞會產(chǎn)生帶正電荷的冰丸，于是在云層的底部聚集成一小片區(qū)域。

【3】大部分的閃電發(fā)生在云層塌陷電荷分離的云層內(nèi)部。但是，隨著雷雨云的發(fā)展，云層下方的地面會帶上正電，閃電就能夠在帶負(fù)電的云和帶正電的陸地之間以放電的形式發(fā)生。擊中地面的閃電是最有可能帶有破壞性的，所以即使它只占所有閃電的20%，還是受到了很大的科學(xué)關(guān)注。

【4】通過高速攝影，科學(xué)家已經(jīng)確定從云層到地面發(fā)生閃電的過程有兩步。首先，要建立連接云層和地面的通道或者路徑。然后強(qiáng)電流會沿著這條通道從云層傳向地面，這股照亮通道的電流就是我們看到的閃電。

【5】電子從云層基部涌向地面就會開始形成通道。當(dāng)這些負(fù)電荷距離地面不到100米的時候，會遇到來自地面的帶正電的粒子流。一旦正負(fù)帶電粒子流相遇，一條連接云層和地面的完整的通道便形成了。這個通道直徑僅有幾厘米，但是已經(jīng)足以使電子以一道閃電這種可見的形式通過通道到達(dá)地面。那些與從云層涌來的電子相遇的帶正電的粒子流通常來自于高大的帶尖頂?shù)慕ㄖ?，例如金屬旗桿或塔。這就是為什么接下來通過完整通道的閃電往往會擊中高層建筑的原因。

【6】一旦通道形成，同一條通道可以發(fā)生多次閃電放電，每一次都是來自云層的電子流在已有通道上遇到帶正電的粒子。但是有時候，通過已有通道的電子流會遇到從地面新路徑來的帶正電的電子流。結(jié)果就是形成在兩處擊中地面的叉狀閃電。

托福閱讀TPO18(試題+答案+譯文)第3篇:Lightning相關(guān)文章：