Question: How does lightning affect TVs?

Nathan Langford answered on 27 Jun 2012:

Hi again,

There are probably lots of ways that lightning could affect TVs, but here are a couple of ideas for you.

1) Electrical equipment is designed to carry “electrical currents”, which are basically flows of free electrons moving around metal circuits. However, lots of components in electrical equipment is only designed to carry a certain amount of current. If you try to push more current through them than they’re designed to take, then you can burn them out or overload them in some way. That’s why if you plug too many things into a single electrical socket, you can put out the power in your house, or even worse things and it can be quite dangerous. Well, lightning is just a flow of very fast moving electrons jumping through the air, which is created by a huge voltage building up during a thunderstorm between two clouds or between a cloud and the ground. Normally, air doesn’t conduct electricity, but if you make the voltage big enough, you can start ripping electrons of the atoms which make up the air (mostly nitrogen with some oxygen) and these get accelerated very quickly towards the ground. Now, the current carried by a lightning strike is huge, so if it hits anywhere which is connected with the electrical circuits in your house, it can overload them and damage them.

2) The chances of this happening for TVs are especially high, because a lot of people still get their TV signals through antennas on the roof of their house or apartment building. Now an antenna is a big metal rod (which is designed to conduct electricity really easily) which is attached to wires which run all the way down through the house and eventually into the ground. Because air doesn’t conduct electricity well, going through the antenna is a much easier way for the electrons flowing in the lightning strike to make it in the ground and so the lightning will often be attracted to hit the antennas instead of the ground. Unfortunately, after hitting the antenna, it normally then passes through the TV on the way to the ground, and this can then damage the TV.

Interestingly, there’s another way that you might think of lightning affecting TVs, but it’s a different type of lightning. It turns out that if you take a look at the old style of TVs (big boxy things), they use a form of lightning to create the TV picture in the first place! They used what is called a “Cathode Ray Tube”, where they artificially create the conditions of lightning, by applying a large voltage between two electrodes in the TV. But they do this in a very controlled way, so that they can create a thin continuous stream of electrons. These would then be sent to run into a layer of fluorescent material on the back of the screen and this can be used to create a picture. But this perhaps also explains why such TVs were particularly susceptible to damage from a lightning strike – a sudden lightning strike when the TV was on would mess up those very controlled conditions which they use to create the picture and maybe even wreck the operation of the TV.