Lightning Revisited [RE-wrenches]

[Antony Tersol]

Drake -

Inductance works not by raising the potential of each of the conductors
a set amount all along the conductor.  Inductance causes an
electromotive force AROUND a circuit which is proportional to the time
rate of change of the magnetic flux through the circuit.  The "magnetic
flux through the circuit" is the amount of magnetic field through the
area of the circuit.  That is why the problems with a large series
circuit in which the wire returning current from the extreme panel does
not return along the same path as the wires connecting the panels.  If a
circuit forms a loop of large area (picture if you will a series circuit
in which the "outgoing" wires connecting the panels are along the top of
the subarray, and the wire returning from the farthest panel is run back
along the bottom of the subarray.  Then the area of the circuit is
roughly the same as the areas of the panels - for a four panel kc120
array approx 40 sq ft) it will have a much larger inductance and larger
potential around the circuit then a circuit of small area (now the
return wire returns right next to the "outgoing" wire, or even spiraled
around it* - for the same four panel array, with a wire separation of
say 1/2 inch, the circuit area would be approx 8 ft x 1/24 ft = 1/3 sq
ft, or 1/120th as much, so for the same lightning strike nearby the
potential differences around the circuit would be 1/120th as much).

*Spiralling the wires around each other is even better because the
direction of the magnetic field relative to the area is relevant.  In
physics/math speak, "the dot product of the magnetic field vector with
the surface normal vector" is the flux.  Spiralling the wires creates
adjacent areas whose fluxes tend to cancel out (assuming the scale of
spatial variation of the magnetic field is relatively larger than the
space scale of the spirals), so that inductance could be reduced by even
larger factors.

(btw, it is precisely this property of inductance that is the foundation
of motors and generators)

Regards,

Antony Tersol

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