Re: Lightning and Body of Metal

On Apr 6, 12:05 pm, "Michael W. Ryder" <_mwry...@xxxxxxxxxxxxxxxx>
wrote:

A problem I have with this is that most metal bodies are not affected by
lightning if they are not grounded.  A car is a good example as the
rubber tires prevent the electricity from going to ground in most cases.

Err, not so. Lightning that has arced through more than a kilometer
of air to an automobile body can easily arc another 15 or 30 cm from
the metal frame to the ground. If the tires have less electrical
resistance than the air, the bolt will go through the tires -
otherwise, it just jumps through the air. Automobile frames do have a
significant effect on a lighting bolt - they act as a conductive
"Faraday cage" that channels the deadly electric current away from any
people who are inside the car - this is why a car is one of the safest
places to be during a thunderstorm - but this has nothing to do with
the rubber of the tires.

In general, any conductor will distort the electric field around it,
so that the field is always perpendicular to the surface. A
consequence of this is that electrical discharges through air can be
attracted to a conductor. If this happens, it will flow through the
conductor and then arc out the other side. So ungrounded conductors
can still get surges of electricity through them from discharges of
enough voltage to arc through the air.

  If the body is grounded it will warm up depending on the voltages,
current, and resistance of the metal body.

Yup. Same with ungrounded metal that happens to have an electric
discharge arcing through it (I guess in this case you could say the
metal becomes momentarily grounded by the electrically conductive
channel of plasma created by the discharge from the metal to ground).

 Look at arc welding for an
example.  Following this idea what would happen if the body of metal was
  holding a metal object in the ground path?  Would they have a chance
of welding together?  A real nasty idea would have metal body A holding
metal body B when the lightning struck.  Could they become welded together?

Heh. That would be fun. "Sorry, Bob. You character is now
permanently welded to his sword." As a GM, I like to encourage
creative thinking like that from my players, perhaps the original
poster can make use of this if his players come up with similar ideas
- letting them weld the mean metal men to the wall or floor, or some
such.

Actually, there's a lot of complexity of how an electrical discharge
interacts with metal which is not represented in the description of
the Lightning spell. Details like a person's metal armor forming a
Faraday cage around him and protecting him, capacitive coupling of the
electric pulse through the armor into the body of the person inside
it, where the "sink" or "ground" is for the bolt (real lightning
doesn't get "thrown", it goes from regions of high electric potential
to low electric potential), the interaction with non-metal armor (this
discharge just arced through meters or more of air, one of the best
insulators around - do you really think it is going to be bothered by
a few millimeters of leather?), skin depth (this is how far an
electric current penetrates in to a conductor - at high frequencies it
tends to be small and hence lightning often travels over the surface
of people that are struck rather than arcing through them and causing
really terrible internal burns), and other details. Trying to account
for or include all this when describing a magic spell would make the
game well nigh unplayable, and also goes against a more mythic and
magical world view where lightning bolts really are thrown from the
heavens (often by angry gods). For these reasons, it is probably best
not to try to go too far into how lightning really behaves when using
magic lightning spells in games.

Luke
.

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