RE: Gap Question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Luke" <Bluu-at-cox-dot-net> 

Antonio:
You mention that a relay with the coil wired in parallel with the
contacts can not be forced into the negative resistance area.  With this
arrangement you are representing a switch that is controlled by a
voltage.  But you are also representing a switch that will shut off as
soon as it conducts or breaks down.  The contacts will close and short
circuit the coil and the contacts will open.

A spark gap will stay on as long as the voltage is still present. So
coil in parallel with the contacts is not a good representation of a
spark gap.


To represent a spark gap you would need to make a circuit that would be
a switch controlled by voltage and be able to stay on after that voltage
has closed the switch like a spark gap.

A better representation might be a relay with a resistor wired across
the normally open contacts and the coil wired in series with this pair.


Applying a voltage to this circuit would result in a current limited by
the series circuit of the resistor and the coil.  Increasing the applied
voltage would continue increasing the current until the coil magnetized
sufficiently to close the contacts.  At this point (breakdown) the
current in the circuit would be limited only by the coil since the
contacts have bypassed the resistor.  So the current would go up and the
voltage applied to the circuit would be the same. So there would be a
negative resistance curve.

So with this arrangement you have:
1.	A voltage controlled switch like a spark gap.
2.	A switch that stays closed after break down like a spark gap
3.	A switch that displays a negative resistance characteristic.

Just wanted to show that standard electronic components could be wired
together and looked at a unit rather than the individual components that
shows a negative resistance curve.


In every mention of the term negative resistance it seems there is a
component of time usually implied assumed etc.  Seems one has to realize
that the term negative resistance is actually referring to:

A decrease (negative) in ohmic value over a period of time when only a
voltage or current is changed to the component.

Am I on the right track here?

SNIP
If the switch is controlled by the voltage over it, as in a relay with
the coil in parallel with its normally open contacts, you
can say that it shows "negative resistance" (put a resistor in series
with the contacts, if you want to try). In this case you can't bias
the device in the negative resistance area not even by forcing current.

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Luke Galyan
Bluu-at-cox-dot-net
http://members.cox-dot-net/bluu