CURRENT-STABILISATION
The working point of the electric current
and voltage will stabilise in point G' and
the underlying mechanism is illustrated in
the figure next to here. Starting in point G
of the characteristic a small increase in
current will cause a more than proportional
drop in the voltage over the discharge
tube. Due to the increased current the
voltage over the resistor will increase as
well but not enough to compensate for the
drop in voltage over the tube. The voltage
source U will try to compensate for the
potential difference by raising the current
through the circuit, causing the voltage
over the discharge tube to drop even
further. In point G'' the voltage drop in
reaction to an increase in current has
become small enough to allow the resistor to compensate fully for the drop of voltage
over the tube. Nevertheless the current keeps rising because the sum of the voltage
over the tube and over the resistor is still lower than the supply voltage U. Only in
point G' the balance is restored and from here on the increase in voltage over the
resistor due to an increase in current exceeds the drop of the voltage over the
discharge tube. A further increase of current is now prevented and current and
voltage will stabilise in G'.
