> But it can't be just a pure conductor because
> that would mean there is nothing for a galvanometer to
> detect.
Sorry, Jim, but I disagree.
Current flowing through a wire always generates a (weak) magnetic field
around the wire. The ammeter used on TR2-early TR6 is not a galvanometer
at all, but instead a "moving vane" movement that responds to that magnetic
field directly. Hence it requires no voltage drop and in fact would still
work even if the segment of wire inside the instrument could be made a
superconductor with no voltage drop.
And it will still indicate (some) with a direct short between the terminals.
In fact, that is exactly what I have on my TR3A, so that the 60 amp
alternator does not peg the 30 amp ammeter. By choosing the short (3
strands of wire stretched terminal to terminal), it acts as a current
divider with the section of wire inside the meter, resulting in only
approximately 1/2 the current flowing through it. Thus it reads 30 when the
actual system current is 60.
Randall
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