职称英语考试

试题来源：职称英语模拟题-卫生类-概括大意

Volts from the Sky

Lightning has caused awe and wonder since oldtimes. Although Benjamin Franklin demonstrated lightning as enormous electricaldischarge more than 200 years ago， many puzzles stillsurround this powerful phenomenon.

Lightning is generated when electrical chargesseparate in rain clouds， though processes are still notfully understood. Typically， positive charges build atthe cloud top， while the bottom becomes negativelycharged. In most instances of cloud-to-ground lightning， the negatively charged lower portion of the cloud repels negativelycharged particles on the ground s surfaces， making itbecome positively charged. The positive charge on the ground gathers atelevated points.

A flow of electrons begins between the cloudand earth. When the voltage charge becomes large enough， it breaks through the insulating barrier of air， and electrons zigzag earthward. We see the discharge as lightning.

Lightning can occur within a cloud， between clouds， or between clouds and theground. The first variety， intra-cloud lightning， is the most frequent but is often hidden from our view.Cloud-to-ground lightning， making up about 20 percentof lightning discharges， is what we usually see.Lightning comes in several forms， including sheet， ribbon， and ball. Intra-cloud lightning canilluminate a cloud so it looks like a white sheet， hence its name. When cloud-to-ground lightning occurs during strong winds， they can shift the lightning channel sideways， so it looks like a ribbon. The average lightning strike is morethan 3 miles long and can travel at a tenth of the speed of light. Balllightning， the rarest and most mysterious form， derives its name from the small luminous ball that appears near theimpact point， moves horizontally， and lasts for several seconds.

Thunder is generated by the tremendous heatreleased in a lightning discharge. Temperatures near the discharge can reach ashigh as 50，000°F withinthousandths of a second. This sudden heating acts as an explosion， generating shock waves we hear as thunder.

About 2，000thunderstorms are occurring in the world at any time， generating about 100 lighting strikes every second， or8 million daily. Within the United States， lightningstrikes are estimated at 20 million a year， or about 22，000 per day. You have a 1-in-600，000 chanceof bring struck by lightning during your lifetime. Lightning can strike twiceor more in the same spot. The Empire State Building in New York is struck bylightning about two dozen times annually.

You can measure how far you are from alightning strike by counting the seconds between viewing the flash and hearingthe bang， and then dividing by five. This approximatesthe mileage.

1. Paragraphs 2 and 3

2. Paragraph 4

3. Paragraph 5

4. Paragraph 6

A Cloud-to-ground lightning occurring in theU.S.

B Types of lightning

C Cause of lightning

D Differences between thunder and thunderstorm

E Frequencies of thunderstorms occurring in theworld and the U.S.

F Shock waves as thunder

5. In most cases of cloud-to-ground lightning， the ground s surface …

6. One form of lightning that … is ball lightning …

7. Cloud lightning looks like a ribbon when itslighting channel …

8. Although not fully understanding processesof lightning， man …

A occurs most infrequently.

B is shifted sideways by strong winds.

C is often hidden from our view.

D is equipped with a good knowledge of variousforms of lightning .

E is estimated at 20 millions a year.

F is positively charged.

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网考网参考答案：C、B、F、E、F、A、B、D
网考网解析：进入考试题库查看解析
大数据分析：根据网考网与考试题库的统计分析，该试题：
19%的考友选择了A选项
39%的考友选择了B选项
6%的考友选择了C选项
7%的考友选择了D选项
28%的考友选择了E选项
1%的考友选择了F选项
考友解析与评论：
 · 悲剧 好多题没有头绪 赶紧做题啊
 · 同样的题比原先难了
 · 这题不解，原来选C、B、F、E、F、A、B、D，感觉挺好的