Anonymous
Anonymous asked in Science & MathematicsPhysics · 1 decade ago

Why is a lightning rod pointed?

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  • 1 decade ago
    Favorite Answer

    Historical reasons, they really should be rounded

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  • nevitt
    Lv 4
    3 years ago

    Lightning Rod Conductor

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  • 1 decade ago

    Benjamin Franklin (1706-1790) found that charges are passed through a grounded metal rod with a pointed end more easily than a blunt end when the distance is 16 cm.

    A lightning rod allows charge to leak off thunder clouds before it builds up sufficiently to create destructive lightning bolts.

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  • 4 years ago

    The taller that lightning rods are, the more effective they are. The surface of a lightning rod is an equipotential ground surface and the nearby non-ground equipotentials follow the shape of the rod. Having the end of the rod pointed packs the equipotentials closer together and makes it easier for ionization to occur when a large lightning induced voltage is nearby, which effectively makes the rod taller and more effective.

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  • Anonymous
    4 years ago

    This Site Might Help You.

    RE:

    Why is a lightning rod pointed?

    Source(s): lightning rod pointed: https://shortly.im/RBK94
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  • Anonymous
    1 decade ago

    A lightning conductor consist of a number of pointed conductors fixed to the top of a building and connected to a thick copper wire.This wire runs down the side of the building and ends on a metal plate burried in the ground.When a negatively charged cloud passes over the building it induces a positive charge on the pointed ends of the lightning conductor and an equal negative charge at the metal plate.Due to DISCHARGING ACTION OF SHARP POINTS, a positively charged electric wind is set up which neutralizes the negative charge of the cloud.The cloud thus passes without harming the building.This is how lightning conductor works .

    The question was about the action of sharp points.This is how sharp points work:---When a spherical conductor of radius r carries a charge q , the surface charge density of charge is given by

    Surface charge density = charge/area = q/ {4 pi (r^2)}

    For a sharp point r is very very small i.e. it tends to zero , therefore surface charge density is very large.The particles of air coming in contact with pointed charged ends get similarly charged and are repelled.In this way an electric wind is set up(This is the electric wind I mentioned in the function of lightning conductor).Thus, the charge is sprayed . This process is termed CORONA DISCHARGE.That is why lightning conductors are made pointed.I hope this is clear.

    Source(s): My Brain
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  • 1 decade ago

    In the United States, the pointed lightning rod conductor, and more accurately the "lightning attractor", was invented by Benjamin Franklin as part of his groundbreaking explorations of electricity. Franklin speculated that, with an iron rod sharpened to a point at the end,

    the electrical fire would, I think, be drawn out of a cloud silently, before it could come near enough to strike [...].

    Franklin had speculated about lightning rods for several years before his reported kite experiment.

    It is commonly believed, erroneously, that a rod ending in a sharp point at the peak is the best means to conduct the current of a lightning strike to the ground. According to field research, a rod with a rounded or spherical end is better. "Lightning Rod Improvement Studies" [2] by Moore et al say:

    Calculations of the relative strengths of the electric fields above similarly exposed sharp and blunt rods show that although the fields, prior to any emissions, are much stronger at the tip of a sharp rod, they decrease more rapidly with distance. As a result, at a few centimeters above the tip of a 20-mm-diameter blunt rod, the strength of the field is greater than that over an otherwise similar, sharper rod at the same height. Since the field strength at the tip of a sharpened rod tends to be limited by the easy formation of ions in the surrounding air, the field strengths over blunt rods can be much stronger than those at distances greater than 1 cm over sharper ones.

    The results of this study suggest that moderately blunt metal rods (with tip height–to–tip radius of curvature ratios of about 680:1) are better lightning strike receptors than are sharper rods or very blunt ones.

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  • 1 decade ago

    if you know some basic things about electric fields, you may know that round things do not concentrate electric field, and are equally strong in all directions, but sharp things concentrate the electric field at the sharp point. if i could draw a picture it might help.

    I beleive the previous to be correct. However, on wikipedia.org, the article on lighting rods suggests they should in fact be rounded at the end. This does not make much sense to me, maybe check into it further.

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  • 1 decade ago

    not all rods are pointed, some of them are round, but i figure its to gather more electricity more efficiently in one spot i figure

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  • 1 decade ago

    if u work out the electrostatics, the electric field diverges at a tip or point. so the lighning will have more probability to strike the tip.

    Source(s): Classical electrodynamics, Landau
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  • 1 decade ago

    the only ones i have seen are spikes on top of our buildings there was one above each room and on the edge of the roof but they were only like 3 feet tall

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