Open question.
Discussion
Last night I caught myself wandering what happens when a convertible gets hit by lighting. My physics is a bit rusty, but I assume you're protected in tin top by the Faraday cage nature of the car.
At a guess, this won't be true for a convertible. Does anyone know if they're "safe". (Ignoring the fact that being hit by lightening is wildly unlikely in the first place). I know the tyres offer a degree of insulation, but I assume lightning has enough power to jump the 6" or so to the ground.
Dan
At a guess, this won't be true for a convertible. Does anyone know if they're "safe". (Ignoring the fact that being hit by lightening is wildly unlikely in the first place). I know the tyres offer a degree of insulation, but I assume lightning has enough power to jump the 6" or so to the ground.
Dan
plotloss: Not quite true, lightning always takes the route of least resistance to earth, as with any electrical transmission. The reason tall objects tend be struck is that they offer a lower resistance than the air. So, if you have a copper conductor 50 metres tall and a tree 70 metres tall it would tend to hit the copper conductor. This also applies to the car/head situation.
Regards.
roadsweeper.
Regards.
roadsweeper.
quote:
plotloss: Not quite true, lightning always takes the route of least resistance to earth, as with any electrical transmission. The reason tall objects tend be struck is that they offer a lower resistance than the air. So, if you have a copper conductor 50 metres tall and a tree 70 metres tall it would tend to hit the copper conductor. This also applies to the car/head situation.
Regards.
roadsweeper.
Well there you go, I stand corrected
Matt.
quote:
I think I remember reading somewhere that lightning actually goes up to the atmosphere, not down to earth? If this is the case then a moving car is perfectly safe.
Very dodgy physics from memory here, but doesn't a very thin "trace" bolt come down from the sky (barely visible) which then makes the connection, and the main "arc" of lightning then follows that trace back up from ground to sky ?
quote:
Very dodgy physics from memory here, but doesn't a very thin "trace" bolt come down from the sky (barely visible) which then makes the connection, and the main "arc" of lightning then follows that trace back up from ground to sky ?
thats my understanding of it too. I think if it cant find a source to 'strike' lightning usually disappears into the atmosphere.
i reckon as there is no faraday cage, you're probably gonna get fried.
>> Edited by toleman on Tuesday 30th July 12:32
quote:
Reaching for the Sky
Before we get ahead of ourselves, we have to consider what is happening with the surface of the earth and objects on the surface. As the step leaders approach the earth, objects on the surface begin responding to the strong electric field. The objects reach out to the cloud by "growing" positive streamers. These streamers also have a purplish color and appear to be more prominent on sharp edges. The human body can and does produce these positive streamers when subjected to a strong electric field as that of a storm cloud. In actuality, anything on the surface of the earth has the potential to send a streamer. Once produced, the streamers do not continue to grow toward the clouds; bridging the gap is the job of the step leaders as they stage their way down. The streamers wait patiently, stretching upward as the step leaders approach.
Next to occur is the actual meeting of a step leader and a streamer. As discussed earlier, the streamer that the step leader reaches is not necessarily the closest streamer to the cloud. It's very common for lightning to strike the ground even though there is a tree or a light pole or any other tall object in the vicinity. The fact that the step leader does not take the path of a straight line allows for this to occur.
After the step leader and the streamer meet, the ionized air (plasma) has completed its journey to the earth, leaving a conductive path from the cloud to the earth. With this path complete, current flows between the earth and the cloud. This discharge of current is nature's way of trying to neutralize the charge separation. The flash we see when this discharge occurs is not the strike -- it is the local effects of the strike.
quote:
quote:
Reaching for the Sky
Before we get ahead of ourselves, we have to consider what is happening with the surface of the earth and objects on the surface. As the step leaders approach the earth, objects on the surface begin responding to the strong electric field. The objects reach out to the cloud by "growing" positive streamers. These streamers also have a purplish color and appear to be more prominent on sharp edges. The human body can and does produce these positive streamers when subjected to a strong electric field as that of a storm cloud. In actuality, anything on the surface of the earth has the potential to send a streamer. Once produced, the streamers do not continue to grow toward the clouds; bridging the gap is the job of the step leaders as they stage their way down. The streamers wait patiently, stretching upward as the step leaders approach.
Next to occur is the actual meeting of a step leader and a streamer. As discussed earlier, the streamer that the step leader reaches is not necessarily the closest streamer to the cloud. It's very common for lightning to strike the ground even though there is a tree or a light pole or any other tall object in the vicinity. The fact that the step leader does not take the path of a straight line allows for this to occur.
After the step leader and the streamer meet, the ionized air (plasma) has completed its journey to the earth, leaving a conductive path from the cloud to the earth. With this path complete, current flows between the earth and the cloud. This discharge of current is nature's way of trying to neutralize the charge separation. The flash we see when this discharge occurs is not the strike -- it is the local effects of the strike.
Blimey....and to think I thought it was God turning the lights on and off!
After posting, I had a quick Google and found these:
www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=lightning+strike+convertible
The universal advice seems to be:
In the absence of a sturdy, frequently inhabited building, any vehicle with a hard metal roof (not a convertible or golf cart) and rolled-up windows can provide a measure of safety. A vehicle is certainly better than remaining outdoors. It is not the rubber tires that make a vehicle a safe shelter, but the hard metal roof which dissipates the lightning strike around the vehicle. DO NOT TOUCH THE SIDES OF THE VEHICLE!
Dan
www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=lightning+strike+convertible
The universal advice seems to be:
In the absence of a sturdy, frequently inhabited building, any vehicle with a hard metal roof (not a convertible or golf cart) and rolled-up windows can provide a measure of safety. A vehicle is certainly better than remaining outdoors. It is not the rubber tires that make a vehicle a safe shelter, but the hard metal roof which dissipates the lightning strike around the vehicle. DO NOT TOUCH THE SIDES OF THE VEHICLE!
Dan
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