The flash of a nearby lightning bolt followed by the crack of thunder can't help but make you take notice of the power of nature. And it's a good thing you get that reminder because lightning kills more people than floods, hurricanes or tornadoes. Some of those deaths are from direct strikes, but most are from the distributed effects of the large surge of current created when lightning hits. That current can make its way through electrical wires into your home, damage your appliances and put you at risk -- your television set is not immune to the danger.
Water and ice droplets can carry an electric charge. During a thunderstorm, clouds separate the charge -- sending the positive charge to the top of the cloud and the negative charge to the base. No one truly understands the mechanism for that charge separation, nor can anyone conclusively state what triggers lightning to start at a specific moment. But what is known is that the charge in the clouds continues to build, creating an electric field between the cloud and the ground. The air between acts as an insulator, preventing current from flowing, but eventually the electric field gets large enough and current flows.
The Power of Lightning
Most lightning occurs when negative current makes its way down to the Earth through the easiest path, approaching the surface step by step. As it gets closer, the negative charge attracts a positive charge from the surface. The positive charge moves upward in streamers. The streamers make an easy path to the surface; when they meet the downward-reaching leaders, the circuit is complete and the bolt of lightning strikes.
The stroke of lightning travels at 100 million kilometers (62 million miles) per hour -- and several strikes can travel the same path so fast the eye sees only a single flickering bolt. That bolt is hotter than the surface of the sun, carries hundreds of thousands of amperes of current and contain 250 kilowatt-hours of energy -- more than a quarter as much energy as the average U.S. home uses in an entire month.
Dangers of Lightning
Lightning brings a lot of electric charge down to the Earth -- that current has to go somewhere. In the same way as lightning seeks the easiest path through the air, the current on the ground will also seek the easiest path. Open water contains electrolytes that make it highly conductive, so the current can easily travel along the surface. Damp ground is also conductive to a certain extent. In both of those situations, though, there is enough natural resistance around that the current dies out quickly. But if the lightning strikes on or near power lines, the current surge can travel along those lines -- lines that lead right to the appliances in your home.
If your television and other appliances are plugged in and an unabated current surge makes its way into your home, the circuits, transformers and wires within can easily be overloaded, melt and even ignite. If you have a cathode ray tube television, the damage to the electrodes can weaken the integrity of the tube and it can implode. If you have a more modern style of television, the effects are unlikely to be as dramatic -- but don't count on the television working after that happens.
You can protect your appliances by unplugging them when a thunderstorm is close. If you live in lightning country, it's also a good idea to install a lightning surge arrester at your home's power panel. For a final layer of protection, you can flip off your home's main circuit breaker during the storm.
About the Author
First published in 1998, Richard Gaughan has contributed to publications such as "Photonics Spectra," "The Scientist" and other magazines. He is the author of "Accidental Genius: The World's Greatest By-Chance Discoveries." Gaughan holds a Bachelor of Science in physics from the University of Chicago.