LIghting is very definetly a regional thing. Around here, we don’t even bother to get out of the pool, much less unplug the phone. Still, all the old churches and public buildings had lightning rods (modern buildings have steel frames, and typically there is an exposed electrical contact at the top).
Here’s a copy of the NASA satellite map: World Lightning Strikes Map AFAIK, the first lighting maps were created in the late 60’s. Before that, everybody had assumed that, apart from topographical variation, it was much the same everywhere.
There are some lovely lighting rods around: I always look. On the chimmny of the Old Engineering School there was a lovely item that (probably for aesthetic reasons) combined the traditional sphere (derived from theoretical analysis) and points (derived from experimentation)
I saw a documentary on lightning that delved into the precursor events of a strike.
There is a branching bunch of streams of ionized air pathways that develop. When one of the branches reaches a good enough conductive potential. Boom. The potential difference floods through that branch.
It may be that your lightning rod protected object is just one of many nearby objects that is in the path of these branches. It might not be the spot that a branch first connects with.
But. If it is. Then I suspect that the very good conductance of the lightning rod system, will conduct it more reliably along that path. Not through other paths in your building.
But. Your lightning rod needs to be the very best path. Just because it is attached to a spike in the ground, does not mean it is the best path. Your water pipes might be the best one. or your electrical system ground, which may be your water pipes as well.
Lightning is a tricky thing. It goes for the best difference between it’s pent up energy and what is near.
A lightning rod system that is grounded by a metal spike in dry earth is often not as good a ground as your water pipes or electrical system ground or neutral.
They are simply more complex lightning rod systems. And they do work very well, in fact, if it weren’t for the lightning arresters, we would be rebuilding our electrical grid every time there was a lightning strike on a pole or substation.
In practice, if a surge of electricity hits the arrester, it blows (like a fuse) and diverts the current through the ground wire to the ground. Best case scenario we only have to replace the arrester and ground wire. Worst case, it was a mutliple hit and 1-2 spans of wire and equipment need to be replaced.
Now, with people cutting and stealing the ground wire (typically copper #4), the grid is more susceptible to lightning damage, including homes. We have to replace grounds with armored cable, especially in the poorer neighborhoods - but that’s another thread.
Mostly TRUE ! The false bit is the strength of the “cannot”. That is not so, it greatly reduces the chances.
Bachelor of Engineering in an electrical field and a nerdy watcher of these nerdy repetitive doco’s .
the answer implies he is interpreting the question like this
"Does the lightning rod reduce damage by connecting the (conductive) roof to the ground ? " Well anyway the important part is that this interperation is
Lighting hits roof
electricity flows through roof to lightning rod
lightning rod conducts it down to the ground.
Well yes it does, the answer is false to say that is wrong
The lightning rod both protects the roof, by allowing the feeler field to be created up there at the sharp end of the lightning rod (sharp ends are more effective than say, grounding a metal roof.)
AND
protects everything under the roof, eg the wall, the electricals and plumbing, and the contents and people inside, etc. by being there to conduct from the roof to the ground.
There are videos of the feeler field, this is a true thing, its the wet air conducting toward the sharp end of the lightning rod or similar sharp conductor
If I remember correctly, the smaller the radius of the point on a lightning rod the less voltage is necessary to create a corona discharge which is a sort of ionized electrical field due to the potential difference between the ground and the cloud. As the cloud above
builds up potential relative to the ground, the size of the corona discharge on the rod increases in proportion. If the build up rate is not too great no lightning bolt will appear to equalize the potential. But if its rapid the corona discharge cannot equalize the potential fast enough to prevent the strike which may or may not hit the rod itself.
You probably correctly remember what you have been taught, but the point of the American Journal of Physics article I cite above is that it’s not really correct – the article not only argues persuasively that the electric field (which is a global phenomenon) is not dictated by the radius of curvature at the tip (which is strictly local). It even goes so far as to provide counterexamples, where the field has no correlation at all with the radius of curvature, or where the field is actually greater for a region where the radius of curvature is smaller.
In any event, it’s irrelevant – lightning rods work perfectly well without sharp tips.
