8—8.
PROBES
’
167
mechanism by which this is started is not shown in the diagram)
and the shaded.area represents the region in which the familiar
'
greenish light appears. The total potential drop across the tube
'
is 30 volts, as shown, and the potential at some point along the
discharge is to be
Although this potential is the
unknown quantity, it is shown in the gure as + 25 volts, for
clarity in the following discussion. In this case, the potential
(Vs) of the gas near the probe with respect to the anode is 30 minus —
25, equals 5 volts.
,
_
The probe circuit is shown in the upper right corner of the
gure 8—9. A Curve of the current (i) and the probe potential (V)
with respeCt to the anode, is shown in gure 8—10. - The current
c
_
-
-
-
"\
'
—
…
/
‘
[=£o€Vfe/ / :
'
-
,
CURRENT DUE ro
/ _—
|
|
_
ELECTRO/VS» REACH/NG
/
'
COLLECTOR
_
POSIT/VE
ION—$»
| }
_—
REACH THE moss
| |
_
Î
»
Ÿ Ÿ
totheanodeelectronsarerepeedWlthh1ghvebütyff°m th?
“
vm1mtyofthepwbeanPosmvemsaf€Sl°“lyamwnt°1tA - :"
pas1twewnsleftmthenelghb0fh@°d°fth€PmbeTheele°“°