The Formation of Lightning - Essay Example

Download file to see previous pages A lightning discharge that involves an object on ground or in the atmosphere is sometimes referred to as a "lightning strike". The term stroke or component stroke apply only to components of cloud to ground discharges. Each stroke involves a downward leader and an upward return stroke, and may involve a relatively low level "continuing current" that immediately follows the return stroke. Transient processes occurring in a lightning channel while it carries continuing current are termed M-components. First strokes are initiated by "stepped" leaders while subsequent strokes formed by previously formed channels are initiated by "dart" or "dart-stepped" leaders (Rakov & Uman: 4).
extreme heat. A lightning bolt is hotter than the surface of the sun. The wild electricity in lightnings when harnessed, produce power supply for human use. Lightnings are of several types (Google image, 2008).
The various stages in the formation of a bolt of lightning (Figure 1.) is as follows: First, cumulonimbus clouds which are towering clouds that spread out on the top, occur between 1,600 and 60,000 feet in the atmosphere, and are associated with heavy thunderstorms, rainfall and lightning. During a thunderstorm, clouds develop a separation of electric charge, with the tops of the clouds positively charged, and the bottoms negatively charged. The production of a lightning bolt begins when the negative charge on the bottom of the cloud gets large enough to overcome air's resistance to the flow of electricity and electrons begin flowing towards the earth in a zigzag, forked path at the speed of about sixty miles per second. This discharge is called a leader and it moves directly towards the ground. As the electrons flow downwards, they collide with air molecules, producing more free electrons. However, this is not the actual lightning bolt that is visible to the human eye (Science 1, 2008).
In the meantime, as the electrons approach the ground, the ground becomes more and more positively charged due to the repulsion of electrons in the ground. This positively charged region moves up through any conducting objects on the ground such as houses, trees, people, into the air. When the electrons moving downwards meet the upward flowing positive regions at an altitude of a hundred meters or so, they form a complete circuit, and the lightning begins. However, the lightning bolt is still forming at this point, and it is not the actual one that is seen. Once the circuit has been formed, it takes less than a millisecond before it is seen as the actual lightning bolt (Science 1, 2008).
In less than a millisecond, upto a billion trillion electrons may reach the ground, the current can be up to 200,000 amperes, and the main act of lightning, the return stroke is then seen. The return stroke which travels at almost half the speed of light, is able to reach three or four miles back up to the cloud, and relieve it of its large excess of negative charge, about 100 quintillion electrons. The channel that was established by ...Download file to see next pagesRead More