-
Asked by rida to Dalya, Derek, Sarah, Tim, Tom on 19 Jun 2011.
-
Sarah Thomas answered on 16 Jun 2011:
Lightning is a sudden discharge of high voltage and high current arising between charged clouds. These surges, in their path towards the earth, can strike power lines and antennae and pass through the wires to the terminal equipment such as TV. The huge currents and voltages, even though of short life, can damage the electrical components and electronic circuits which are usually designed for low power. The surges are so powerful that they can destroy the equipment even if they are off but connected to the mains.
-
-
Derek McKay-Bukowski answered on 16 Jun 2011:
If electric current passes through something, it heats up. This is called Joule Heating. Lightning, as Sarah explained, results in huge electrical currents. Because Joule Heating is proportional to the square of the current, then things that have the electrical current passing through them also get hot.
In the case of lightning striking a tree, if the trunk is damp from the sap or the rain, this moisture can boil instantly, causing parts of the tree to blow off explosively. (Which is one of many good reasons not to stand under a tree during a storm!) The electronics and wires in a television can be subjected to the same thing. They might not explode, but they could over heat and burn out.
However, there is another effect. As Sarah also said, there is a high voltage involved. This voltage can be so high that it can cause semiconductors to break down. In fact, that’s how lightning discharges occur… it is the electrical breakdown of air (often triggered by cosmic rays). Anyway, this high voltage can also cause problems for the sensitive microelectronics in a television set.
Also, don’t forget that the lightning doesn’t have to be a direct hit. If a current is flowing through something, it can “induce” a current in a nearby thing. This is why you should be careful with coiled power cables.
Additionally, as the lightning strikes the ground, it can cause a power surge up the “earth wire” in a house. Even though something might be switched off, if it is still plugged in, this earth wire (working in reverse) will bring power into the house, potentiallyburning out anything attached to it.
Modern wiring is designed to try to minimise these risks. But there is always still a chance for a nearby strike to do some VERY serious damage.
-
Tim Millar answered on 16 Jun 2011:
As kids we always were told to turn the TV off during the lightening storm to stop it coming through the ariel and into the house. It never did though
-
Tom Crick answered on 19 Jun 2011:
A lightning strike (a sudden discharge of high voltage/high current due to atmospheric conditions) would certainly damage electronics depending on whether the fuses in your house tripped. If you did get a lightning strike on your aerial, this may blow the TV, but it would be very rare — in most areas there are other paths of least resistance for the strike.
In the good ol’ days of using modems to connect to the Internet, you were always advised to unplug your computer if there was lightning, as a strike on a telephone pole could travel and fry the motherboard (but in retrospect, this is as unlikely as an aerial strike!).
Comments