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Posted 30 March 2012 - 02:59 PM
I've always been wild about watching thunderstorms and lightening. When I was little and it would storm, my mom would come in my bedroom at night and close the curtains, so I wouldn't be afraid, but as soon as she would leave I would get up and open them again so I could watch the storm. I always thought the light show was really cool.
Now getting struck by lightening would be pretty terrible. I've come close to that natural disaster twice. Once as a child while riding a pony, it struck close enough I felt the heat of the flash, so did the pony, and it reared and nearly dumped me, and another time just a few years ago, I was standing out by the front door of the kennel watching a storm, and like a dummy I had my arm resting on the pen next to me, and I felt the tingle come threw the wire when a lightening bold struck the ground nearby. Since then I make sure I'm not touching any fences while storm watching. We live on a hilltop, so while I don't have to worry about floods, we are frequently hit by lightening here. I can't count the number of telephones we have lost. Several computers too, if I happen to be away and can't shut them down.
Posted 06 April 2012 - 04:11 AM
Lightning occurs because of a difference in electrical charges between the clouds and the ground. I guess I have to read more about how the charges form and why the electrical breakdown of the air between the clouds and the ground occurs instead of a lightning striking through nearby metal objects, because logically speaking that is the path of least resistance and as we know it, electricity flows more readily through the path of least resistance with very little of the electricity flowing through paths of higher resistance. Perhaps the breakdown of the electrical properties of air when a lightning just begins causes an erratic path for the electrical breakdown of the air to continue as a chain reaction, but it might as well have been the heat from the initial electrical breakdown that causes the adjacent air to have an electrical breakdown in turn causing a chain reaction till the lightning bolt is seen hitting the ground.
I have once had my television go boom because of lightning hitting the antenna cable. It sounded like glass shattering but when I looked around, I didn't see anything broken anywhere. It is only much later that I realised it was the television. Ever since, I got a surge protector for the antenna cable and later switched to using a digital receiver with a shielded cable leading to a directional dish mounted on a wall. I have not had any surge damaging equipment because of lightning striking an overhead electrical cable or a telephone line and I often wonder why - the electrical cables are more likely to get hit, seeing how they are constantly alternating between positive and negative charges. When the electrical line has a charge opposite to that of the clouds, it ought to be increasing the possibility of lightning, but we haven't had any lightning striking the electrical cables yet. The telephone cables are shielded with plastic covering but they are hanging along trees and short poles and are just as likely to get hit by lightning, by the path-of-least-resistance theory.
By the way, for the folks out there who think that all of the electricity should flow through the path of least resistance, let me present you with an example. Think of a stream of water, perhaps in a river. Now, imagine that there is a rock somewhere close to the river bank but with enough space between the rock and the river bank so as not to stop the flow of the water completely. Now, with the flow of the water, leaves, branches of trees, algae, fungi, and other matter gets accumulated between the rock and the river bank creating a kind of a blockage. However, this blockage does not completely stop the water from flowing - you would still see some flow through the leaves and other debris that is reducing the flow of the water within the small gap. The phenomenon is exactly the same when examined in the flow of electricity - the electricity flows in a greater quantity along the path of lower resistance but there still is some flow of electricity along the paths of higher resistance. There may be a threshold beyond which the electricity flow along the paths of higher resistance ceases completely because of the greatness of the resistance and such a case can be observed when you notice that some gaps are not air tight but they are water tight. I believe an umbrella has material treated with a chemical substance to reduce the gaps to such an extent that the gaps permit the flow of air but not the flow of water, possibly a case that is analogous to the manner in which the plastic shielding on cables prevents the flow of electricity even when two wires that are shielded with plastic are connected to the opposite terminals of a battery are placed over each other.
Posted 06 April 2012 - 04:51 AM
Theoretically there is no absolute threshold of insulation - remember, we are in quantum-land where Shroedinger's wavefunction takes over and particles can be everywhere, nowhere and both at the same time :-) In real life it obviously depends on how much 'kick' (voltage) you want and, crucially, whether you want DC oir AC.
The water analogy is good for the basics of DC current-flow, but not so good for AC and semiconductor theory....
CHeck it out
Posted 07 April 2012 - 12:32 AM
Posted 08 April 2012 - 09:51 AM
Posted 08 April 2012 - 10:25 AM
arge 'seeking' the path of lowest resistance, until one grounds out and you get the main discharge.
Edited by Bikerman, 08 April 2012 - 10:27 AM.
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