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One of the most stunning electrostatic phenomena are lightning strikes that accompany electrical storms. Thunderclouds often have a positively charged upper portion, a negatively charged lower portion (each charge being approximately 30 coulombs) and a neutral central area. The negatively charged base of the cloud induces a corresponding positive charge on the earth below the cloud. This in turn sets up a strong electrical field between the cloud and the earth. Forked lightning flashes occur when the electrical field is so great that the air ionizes, or breaks up into positively and negatively charged ions. The positive ions flow up to the base of the cloud, neutralizing the negative charge there, while the negative ones flow down to earth, neutralizing the induced positive charge there: this ionization is visible as the lightning flash.

The transfer of such a large charge over such a short period of time produces temperatures in the air as high as 30 000 K. This sudden heating causes the air around the strike to expand rapidly, setting into motion an intense longitudinal vibration of the air, which can be heard as thunder. Since light travels much faster than sound, to a distant observer the thunder will arrive much later than the lightning. Obviously if one were struck by lightning, the lightning and thunder would occur almost simultaneously, but unfortunately one would unlikely notice this phenomena if one were in such a situation. As lightning strikes a building, it will flow to earth through the stonework and produce intense heat. Any moisture in the lightning’s path will boil, producing pockets of high-pressure steam, which can easily crack the masonry, often causing severe structural damage to the building. This is where lightning conductors come in. They consist copper strips reaching from the highest point of the building to the earth causing any lightning charge to flow directly to the ground, leaving the building unaffected.

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