The Nezperce herald. (Nezperce, Idaho) 1900-1957, 1922-10-05

grid, determine the value of E. e is
The negative potential which must be-
applied to the grid in order to reduce
he plate current to zero. The value
dF, which is the positive grid poten-
na that will cause the maximum or
situation current to flow in the plate
circuit is also determined by the rela-
tive position of the grid with respect
% the filament and plate. If the grid
Is Of very fine mesh, the value of K
Is small because the eIectrons in pass
ng through the small mesh of the
Wd on their journey from the fila
nent to the plate will negatively
charge the grid and will be repealed.
Slmllarly a small positive charge APP
pued to a fine mesh will tend to ac-
eeerate the velocity of the electrons.
In case of very coarse mesh grid,
ne electrons can pass through the ap-
H1ures In the grid without coming in
70 close to the charge on it and
leatvely high potential will be re- ,
CURED on the grid to control the cleo
aOn stream, or in other words, the
current flowing in the plate circuit.
referring to Fig. VIII, O-G, is the |
current that will flow in the plate cir
eull when there is no potential APP |
phed to the grid. Suppose a positive
~ as OF is applied to the grid
ine corresponding plate circuit current |
VIZ be I'D or BID, more than it was
'aen the grid had no potential APP
lied to it.
a negative potential of OH rs now
pplled to the grid where OH is cqual
saiue to Oh, but opposite in sign.
ne application of the negative POI
ulial when applied to the grid will
'use the plate current to be reduced
a value He or A-C, less than it
as When there was no potential ap-
led 70 the grid. SO it is seen that
sa'lVe potential when applied to the
y uoes not reduce the plate circuit
rent as much as the same positive
'enlial increased the plate circuit
rent. This irregular conductivity of
'uoe is made use of when the tube
aseo as detector or rectifier of
10 signals.
.ne incoming radio signal is a high
,uency alternating current. Let us
y an alternating difference of po-
lia whose maximum positive val
: equal to Oh and whose maximum !
a'iVe value is equal to OH, to the :
Vi the three-electrode tube ,
4 - characteristic curve is the same +
lnat Shown in Fig. VIII. In Fig.
. SHOWN the alternating difference d
potential applied to the grid.
'ugh the first quarter of a cycle,
zero at J to a maximum mega :
value at X, equal to OH, the .
circuit current will vary from
i's value at z when no grid po- .
[C4 :
nns the next quarter of a cycle
siiu potential changes from :
uium negative value at X to zero, d
Inc corresponding values Of :
circuit current are shown by the
On of the plate current curve :
ring the next or third quarter
eseie the applied grid potential :
uses from zero at L to maxi /
positive value at M, equal to :
nu causes the plate circuit to in
from I-B, its value when the
polential Is zero, to I'D, an in
IN plate current equal to BID.
ing the remaining fourth quar-
cycle as the applied grid POI !
varies from maximum posi-
aiue at M to zero at N, the plate :
current varies from a value S
uining that the characteristic
as Shown in Fig. VIII and Fig.
- with a potential of 40 volts
Plate, then, if the plate current
oe reduced to zero by a varia-
plate voltage-with no poten-
lpplied to the grid-the plate
: must be reduced to zero or
ion or 40 volts must be made. ! e