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3. Technical data
Filament voltage:
Filament current :
Anode voltage:
Anode current:
Grid voltage:
Grid current:
Glass bulb:
Total length:
4. Operation
To perform experiments using the triode, the
following equipment is also required:
1 Tube holder S
1 Power supply 500 V (115 V, 50/60 Hz) 1003307
or
1 Power supply 500 V (230 V, 50/60 Hz) 1003308
1 Analogue multimeter AM51
4.1 Setting up the tube in the tube holder
The tube should not be mounted or removed
unless all power supplies are disconnected.
•
Press tube gently into the stock of the holder
and push until the pins are fully inserted.
Take note of the unique position of the guide
pin.
4.2 Removing the tube from the tube holder
•
To remove the tube, apply pressure with the
middle finger on the guide pin and the thumb
on the tail-stock until the pins loosen, then
pull out the tube.
5. Example experiments
5.1 Generation of charge carriers by a hot
cathode (thermionic effect) and deter-
mining the polarity of the charge carriers
so emitted
•
Set up the circuit as in Fig. 1.
•
Set the anode voltage U
When the grid voltage U
rent is about 0.4 mA.
•
Set the grid voltage U
If the voltage of the grid is positive with respect
to the anode, the anode current I
bly increased. If the grid is negative with respect
to the cathode the anode current decreases.
A heater filament generates charge carriers.
Current flows between the cathode and the an-
ode. The charge carriers must be of negative
polarity because when the grid is negative with
respect to the cathode the flow of current de-
7.5 V max.
3 A approx.
500 V max.
400 V and U
6.3 V
U
A
F
0 V, I
0.4 mA approx.
U
G
A
+8 V, I
0.8 mA approx.
U
G
A
-8 V, I
0.04 mA approx.
U
G
A
± 10 V
typ. I
= 0.9 mA at U
G
7.5 V, U
= 300 V
A
130 mm diam. approx.
260 mm approx.
1014525
1003074
to 400 V.
A
is 0 V the anode cur-
G
to +10 V resp. -10 V.
G
is considera-
A
creases and when it is positive, the flow of cur-
rent increases.
5.2 Recording triode characteristics
•
Set up the circuit as in Fig. 1.
•
– U
characteristics: for constant grid volt-
I
A
A
ages, determine the anode current as a
function of the anode voltage and plot the
values in a graph (refer to Fig. 2).
•
– U
characteristics: for constant anode
I
A
G
=
voltages, determine the anode current as a
F
function of the grid voltage and plot the val-
ues in a graph (refer to Fig. 2).
5.3 Generating cathode rays
•
Set up the circuit as in Fig. 3 so the anode
and cathode form a diode.
•
Raise the anode voltage U
and measure the current flowing at the an-
ode.
The current decreases at higher voltages since
the positive potential of the grid causes it to
capture electrons causing an increase in the
current passing through the grid itself. Voltages
greater than 100 V can lead to the destruction of
the grid.
Electrons accelerated by higher potentials be-
tween the grid and the cathode can be detected
beyond the grid (cathode rays). Increasing the
voltage leads to higher currents which indicates a
greater number of electrons being accelerated.
5.4 Triode amplifier
Also required:
power supply
1 AC/DC
or
power supply
1 AC/DC
Resistor
1
1 MΩ
1 Oscilloscope
•
Set up the circuit as in Fig. 4.
•
Apply an anode voltage U
The oscilloscope is used to demonstrate the
amplification in the signal across the resistor.
•
Repeat the experiment using a variety of
resistors.
Lower AC voltages at the grid lead to greater
changes in voltage across a resistor connected
in circuit with the anode. The amplification gain
increases with the size of the resistor.
5.5 Generation of undamped LC oscillations
Also required:
1 Helmholtz pair of coils S
1 Capacitor 250 pF or 1000 pF
1 Oscilloscope
Warning!
When
switched on, the metal parts of the coils are
live. Do not touch!
2
from 10 V to 80 V
A
12 V (115 V, 50/60 Hz)
1001006
12 V (230 V, 50/60 Hz)
1001007
of about 300 V.
A
1000611
the
anode
voltage
is
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