In Toronto CN Tower hit by lightning 15 times During 24 August 2011 Storm. (Amazing Video)
Muhammad Ikhlaq Siddiqui
Minister (2k+ posts)
wow!!!!!!!!!
hans
Banned
The Mechanics of a Lightning Strike
As the static charge buildup in a storm cloud increases, the electric field surrounding the cloud becomes stronger. Normally, the air surrounding a cloud would be a good enough insulator to prevent a discharge of electrons to Earth. Yet, the strong electric fields surrounding a cloud are capable of ionizing the surrounding air and making it more conductive. The ionization involves the shredding of electrons from the outer shells of gas molecules. The gas molecules that compose air are thus turned into a soup of positive ions and free electrons. The insulating air is transformed into a conductive plasma. The ability of a storm cloud's electric fields to transform air into a conductor makes charge transfer (in the form of a lightning bolt) from the cloud to the ground (or even to other clouds) possible.
A lightning bolt begins with the development of a step leader. Excess electrons on the bottom of the cloud begin a journey through the conducting air to the ground at speeds up to 60 miles per second. These electrons follow zigzag paths towards the ground, branching at various locations. The variables that affect the details of the actual pathway are not well known. It is believed that the presence of impurities or dust particles in various parts of the air might create regions between clouds and earth that are more conductive than other regions. As the step leader grows, it might be illuminated by the purplish glow that is characteristic of ionized air molecules. Nonetheless, the step leader is not the actual lightning strike; it merely provides the roadway between cloud and Earth along which the lightning bolt will eventually travel.
As the electrons of the step leader approach the Earth, there is an additional repulsion of electrons downward from Earth's surface. The quantity of positive charge residing on the Earth's surface becomes even greater. This charge begins to migrate upward through buildings, trees and people into the air. This upward rising positive charge - known as a streamer - approaches the step leader in the air above the surface of the Earth. The streamer might meet the leader at an altitude equivalent to the length of a football field. Once contact is made between the streamer and the leader, a complete conducting pathway is mapped out and the lightning begins. The contact point between ground charge and cloud charge rapidly ascends upward at speeds as high as 50 000 miles per second. As many as a billion trillion electrons can transverse this path in less than a millisecond. This initial strike is followed by several secondary strikes or charge surges in rapid succession. These secondary surges are spaced apart so closely in time that may appear as a single strike. The enormous and rapid flow of charge along this pathway between the cloud and Earth heats the surrounding air, causing it to expand violently. The expansion of the air creates a shockwave that we observe as thunder.
Did it cause any damage to the tower though? How did it survive after being hit so many times by this kind of lightning?
It did not cause any damage because of a system used in buildings since so long. Read the following short article:
Introduction:
The lightning arrester (or) the lightning conductor is a commonly used device which is used to save tall buildings and towers from the attack of lightning.
Principle:
The basic principle behind this life saving system is the "action of points" (or) "corona discharge". It is nothing but the discharge (or) leakage of electric charges from the sharp points of a charged conductor.
Construction:
The apparatus consists of a long thick rod made up of copper which is a very good conductor of electricity so that it can allow a large amount of charges to flow through it. This copper rod passes through the walls of the building. The upper end of the rod is provided with a metal plate having a number of sharp spikes which are visible at the top of the building while the lower end is connected to a plate of copper which is deeply buried in the ground so that the excess of charges is passed to the earth which is a good conductor of electricity and this process is called "earthing".
Function:
The working of a lightning arrestor can be explained either with a positively charged cloud commonly called "male cloud" or with a negatively charged cloud commonly called "female cloud". Consider a negatively charged cloud which passes over the building with a lightning arrestor. Due to the negative charge of the cloud, positive charges are induced to the sharp spikes which are at the top of the building. Now, due to the principle of action of points, leakage of the positive charges from the sharp spikes occurs so that the nearby atoms in the space are ionized into positive and negative charges. Now, the positive charges in the sharp spikes repel the newly formed positive ions and these ions try to neutralize the negative charge of the cloud. If the negative charges are not completely neutralized, these charges due to the attraction of the positive charges in the sharp spikes are passed through the copper rod to the ground where they are earthed. Thus, the intensity of lightning can be reduced thus saving the building from its destructive attack. A lightning conductor can save its surroundings for more than half a kilometer from the attack of lightning.
Usage:
Today, the lightning conductor is used almost in all tall buildings, towers and other tall spots. Hence, it is really a life saving system.
To understand more here is a simple picture about the system.
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