Electrostatics-Lighnting Rods

From the Sky to the Ground

What is a Lightning Rod?

We have all heard of a lightning rod, but what exactly is it? Well, a lightning rod is made up of metal or some other conductor, that is put on the top of a building. There is then a cable that connects the pointed metal rod, to a grounding peg that is buried deep within the Earth (Zavisa).
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(Lightning Rods)

The Two Uses of Lightning Rods

Lightning Be Gone!

Did you know that the primary purpose of lightning rods is too prevent lightning rather than attract lightning? The lightning rods acomplish this in four steps:


  1. The negatively charged cloud promotes induced charge separation, all the electrons in the Earth go as far away from the cloud as possible because the like charges repel. There is an now an overwhelming mass of positive at the surface of the Earth.
  2. The electrons in the lightning rod go as far away from the negative cloud as possible. However, the object is also connected to the ground, which allows the electrons to be discharged in the process of grounding. They are discharged because they repel the cloud so much, they look for the escape root out. This then leaves the lightning positively charged. In other words, the lightning rod gains a positive charge by induction
  3. The air above becomes ionized, positively, because the rod is now positive, therefore it attracts the electrons towards it (and they repel the cloud that is negative). And since the rod is a conductor, it allows the electrons to transfer through it. However, after this transfer, the rod is almost immediately positively charged, as the negative cloud is still there, pushing them away. The positive in the air is attracted to the negative cloud, neutralizing the cloud somewhat, as there is now more positive charge in the cloud ("Lightning Rods Part 1").


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(Blake)

The Overpowering Negative

  • Sometimes the charge neutralization omitted from the lightning rod is not enough to prevent lightning.
The lightning however, likes to hit the highest thing possible, as the electrons want the quickest path to the ground. The lightning rod provides a low-resistenant path to the ground. This is because the lighting rod is a conductor, a conductor is a substance that allows the electrons to transfer through it. This means the electrons are able to move through the lightning rod, until they reach the ground. The lightning rod is a way of discharging the electrons into the Earth in a process called grounding, making the rod neutral once more. Grounding occurs because the Earth is a conductor, and because of its massive size, will stay neutral even if it loses or gains electrons (Zavisa).
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(Edvard)

Fun Facts

  • The lightning Rod on the Empire State Building is the most well known lightning rod ("How Do Lightning Rods Work?")
  • It is often debated whether or not the lightning rod works better with a pointed tip or rounded ball tip, however recent evidence suggests that the rounded tip works better ("How Do Lightning Rods Work?").
  • If lightning hit an insulator, for example a house, there is a high probability that the house would catch fire. This is because lightning generates massive amounts of heat energy. The insulator does not have the ability to transfer and disperse the heat energy. Hence, the heat energy builds up in the insulator, which can lead to temperatures up to five hundred degreas celsius (Zavisa).
  • Nobody knows what causes the negative build up of electrons in the clouds, we only know it occurs ("Lightning Rods Part 1." )
  • The lightning rod was first invented by Benjamin Franklin over a thousand years ago ("How Do Lightning Rods Work?").
  • Most people believe that lightning rods attract lightning (Zavisa).

References


Blake, Leesa, Michael Mazza, Alex Mills, Frank Mustoe, Jim Ross, and Thomas Stiff. On Science 9. Whitby: McGraw-Hill Ryerson, 2009. Print.


Edvard. "Transient Voltage Surge Suppressors." Electrical Engineering Portal RSS. Electrical Engineering Portal, 1 Dec. 2011. Web. 10 Feb. 2013.


"How Do Lightning Rods Work?" AccuWeather.com. Accu Weather, 30 June 2012. Web. 8 Feb. 2013.


"Lightning Rods Part 1." YouTube. YouTube, 15 Aug. 2011. Web. 10 Feb. 2013.


"Lightning Rods." Wikipedia. Wikipedia, 21 Feb. 2013 Web. 12 Feb. 2013.


Zavisa, John. "How Lightning Works." HowStuffWorks. A Discovery Company, n.d. Web. 10 Feb. 2013.