外語等級考試綜合類概括大意
SLightning has caused awe and wonder since old times. Although Benjamin Franklin demonstrated lightning as enormous electrical discharge more than 200 years ago, many puzzles still surround this powerful phenomenon.
Lightning is generated when electrical charges separate in rain clouds, though processes are still not fully understood. Typically, positive charges build at the cloud top, while the bottom becomes negatively charged. In most instances of cloud-to-ground lightning, the negatively charged lower portion of the cloud repels negatively charged particles on the ground s surfaces, making it become positively charged. The positive charge on the ground gathers at elevated points.
A flow of electrons begins between the cloud and 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 the ground. 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 percent of lightning discharges, is what we usually see. Lightning comes in several forms, including sheet, ribbon, and ball. Intra-cloud lightning can illuminate 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 more than 3 miles long and can travel at a tenth of the speed of light. Ball lightning, the rarest and most mysterious form, derives its name from the small luminous ball that appears near the impact point, moves horizontally, and lasts for several seconds.
Thunder is generated by the tremendous heat released in a lightning discharge. Temperatures near the discharge can reach as high as 50,
-
考試作文精品4篇
在生活、工作和學習中,大家對作文都再熟悉不過了吧,作文根據體裁的不同可以分爲記敘文、說明文、應用文、議論文。你所見過的作文是什麼樣的呢?下面是小編收集整理的考試作文4篇,僅供參考,希望能夠幫助到大家。考試作文篇1從一年級開始,考試對於我來說,是一種恐懼。只...
-
考試之後作文(實用6篇)
在平平淡淡的學習、工作、生活中,大家一定都接觸過作文吧,作文是由文字組成,經過人的思想考慮,通過語言組織來表達一個主題意義的文體。一篇什麼樣的作文才能稱之爲優秀作文呢?下面是小編爲大家整理的考試之後作文6篇,歡迎閱讀,希望大家能夠喜歡。考試之後作文篇1“叮...
-
考試的滋味作文範例(9篇)
在我們平凡的日常裏,大家總少不了接觸作文吧,作文根據寫作時限的不同可以分爲限時作文和非限時作文。寫起作文來就毫無頭緒?下面是小編爲大家收集的考試的滋味作文9篇,僅供參考,希望能夠幫助到大家。考試的滋味作文篇1考試像一個調味盒,裝的東西並不多,但卻俱全了酸、...
-
考試之後作文8篇[經典]
在學習、工作、生活中,大家總少不了接觸作文吧,根據寫作命題的特點,作文可以分爲命題作文和非命題作文。寫起作文來就毫無頭緒?以下是小編整理的考試之後作文8篇,歡迎閱讀,希望大家能夠喜歡。考試之後作文篇1學校剛剛舉行完盛大的階段考試,把剛上高中的我,考得迷迷糊糊...