| MadSci Network: Earth Sciences |
If lightning strikes close to electronic equipment it can have a impact on the operation of the equipment. The immediate area around a lightning strike has a high amount of electromagnetic radiation. Therefore, it is very possible that anything electronic will be adversely affected. As far as I know, there is no easy way to determine if the reason for failure of a particular piece of electronic equipment is due to the result of a close lightning strike. Another Mad Scientist wrote: Hi Melvin! When lightning strikes, a high voltage surge can be produced in the power lines and telephone lines, and this surge can sometimes travel for many miles. If the surge is brief, it will not cause obvious charring, yet electronic parts can easily be damaged by microscopic "charring" down inside the individual parts. The ICs in computers are particularly sensitive to high voltage because their transistors contain microscopically thin layers of glass. The glass is so thin that just a few tens of volts can cause a small spark to jump through the glass. When this happens, a hole is blown through the glass layer, and the conductive layers on either side of the glass can touch together. In technical language, the transistor has been "fried". ;) Also, many types of electronic parts (diodes, transistors, ICs) contain extremely thin internal wires which connect the silicon components to the heavier external wires. A large surge of electric current can vaporize the thin wires in the same way as a fuse is vaporized by overcurrent. Equipment which is disconnected from wall outlets and phone lines is relatively immune to lightning damage. However, lighting energy is is not just delivered by an electric current in the power lines and phone lines. The path of the lightning current also is surrounded by an extremely powerful and rapidly changing magnetic field. I metal objects are immersed in a magnetic field, and if the field strength suddenly changes, it will "induce" a voltage across the metal objects, and can create a pulse of electric current through them. If the lightning takes a path which travels very close to an electronic device, the magnetic field can create a pulse of voltage and current in the components within the device. Since these fields become weaker with distance, all this would probably only happen if lightning struck the building. If your computer, stereo, etc., has wires attached to it, these wires can act as an antenna which "gathers" a larger pulse of current from the lightning's magnetic field. For example, if a stereo amplifier is disconnected from AC power, but if there are long wires attached to distant loudspeakers, the long speaker wires can cause trouble. They can pick up the lightning's magnetic "signal", and this signal may pack enough power that it can damage the output transistors in the amplifier even if the amplifier is unplugged from AC power. Another possibility: in theory, the magnetic field from the lightning strike can erase computer hard drives, floppy disks, etc. If a computer dies because of lightning, look into the possibility that the hard drive's tables, boot track, or system software was partially erased. (Note that other valuable data on the hard drive might still be OK, so don't just format the whole thing if you want to retrieve this data.) About determining the source of damage: if your equipment worked fine just before a lightning storm, but then it was no longer working after the storm, then lightning is very probably the cause. If the equipment was totally disconnected from all long cables, yet it still was damaged, yet lightning did not strike your building directly, then the cause of the failure is not as clear-cut. see http://www.eskimo.com/~billb/ele-edu.html for my list of articles about electricity ((((((((((((((((((( ( ( ( ( (O) ) ) ) ) )))))))))))))))))))) William J. Beaty DESIGN ENGINEER beatywj@ch.etn.com INDUSTRIAL PHOTOCONTROLS EATON/CUTLER-HAMMER Everett, WA 206-353-0900
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