3B SCIENTIFIC PHYSICS U19151 Instrucciones De Uso página 8

3. Technical data
Filament voltage:
Filament current:
Anode voltage:
Anode current:
Grid voltage:
Glass bulb:
Total length:
4. Operation
To perform experiments using the triode, the fol-
lowing equipment is also required:
1 Tube holder D
1 DC power supply 0 – 500 V
or
1 DC power supply 0 – 500 V
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.
•
Push the jaw clamp sliders on the stanchion of
the tube holder right back so that the jaws
open.
•
Push the bosses of the tube into the jaws.
•
Push the jaw clamps forward on the stanchions
to secure the tube within the jaws.
4.2 Removing the tube from the tube holder
•
To remove the tube, push the jaw clamps right
back again and take the tube out of the jaws.
5. Example experiments
5.1 Generation of charge carriers by a hot cath-
ode (thermionic effect) and determining the
polarity of the charge carriers so emitted
•
Set up the circuit as in Fig. 1. Connect the mi-
nus pole of the anode voltage to the 4-mm
socket marked with a minus.
•
Set the anode voltage U
When the grid voltage U
about 0.4 mA.
•
Set the grid voltage to +10 V resp. -10 V.
If the voltage of the grid is positive with respect to
the anode, the anode current I
7.5 V max.
3 A approx.
500 V max.
U 400 V and U 6.3 V
A F
U 0 V, I 0.4 mA approx.
G A
U +8 V, I 0.8 mA approx.
G A
U -8 V, I 0.04 mA approx.
G A
± 10 V max.
130 mm diam. approx.
300 mm approx.
U19100
U33000-115
U33000-230
U17451
to 400 V.
A
is 0 V the anode current is
G
is considerably
A
increased. If the grid is negative with respect to the
cathode the anode current decreases.
A heater filament generates charge carriers. Cur-
rent flows between the cathode and the anode. The
charge carriers must be of negative polarity be-
cause when the grid is negative with respect to the
cathode the flow of current decreases and when it
is positive, the flow of current increases.
5.2 Recording triode characteristics
•
Set up the circuit as in Fig. 1. Connect the mi-
nus pole of the anode voltage to the 4-mm
socket marked with a minus.
•
I – U characteristics: for constant grid volt-
A A
ages, determine the anode current as a func-
tion of the anode voltage and plot the values
in a graph (refer to Fig. 2).
•
I – U characteristics: for constant anode volt-
A G
ages, determine the anode current as a func-
tion of the grid voltage and plot the values in a
graph (refer to Fig. 2).
5.3 Generating cathode rays
•
Set up the circuit as in Fig. 3 so the grid and
cathode form a diode. Connect the minus pole
of the anode voltage U
marked with a minus.
•
Raise the anode voltage U
and measure the current flowing at the anode.
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 between
the grid and the cathode can be detected beyond
the grid (cathode rays). Increasing the voltage leads
to higher currents which indicates a greater num-
ber of electrons being accelerated.
5.4 Triode amplifier
Also required:
1 AC/DC power supply 0 – 12 V
or
1 AC/DC power supply 0 – 12 V
1 Resistor 1 MΩ
1 Oscilloscope
•
Set up the circuit as in Fig. 4. Connect the mi-
nus pole of the anode voltage to the 4-mm
socket marked with a minus.
•
Apply an anode voltage U
The oscilloscope is used to demonstrate the ampli-
fication in the signal across the resistor.
•
Repeat the experiment using a variety of resis-
tors.
2
to the 4-mm socket
A
from 10 V to 80 V
A
U8521105-115
U8521105-1230
of about 300 V.
A