Thermionic Emission

Procedure First part of the experiment. Second part of the experiment. Objective. Theory. Thermionic emission definition. Equipment. Procedure. First part of the experiment. Second part of the experiment. Results/data. Conclusions. References.

The objective of this laboratory work was to investigate the thermionic emission of an operating vacuum tube diode and determine the work function of the cathode material.

For this work a vacuum diode was used, a variable power supply for heating the cathode, a variable power supply that provided power for the vacuum tube, an ammeter and a voltmeter for measurement of the heating current and voltage, and a milliAmmeter and voltmeter for main power supply current and voltage measurement. The schematic of the equipment is shown in fig 1.

The heating voltage (Uh1) was set to 4.78 Volts with a current (Ih1) of 1.1 Amps

After recording the readings of the milliAmmeter (I) the anode voltage was increased by 1 Volt and the readings of the milliAmmeter were recorded again.

The voltage was raised by 1 Volt, recording the current after every increase of voltage, up to 15 Volts, resulting in a total of 15 recorded measurments.

The current readings that no longer increased with an increase in voltage were recorded as the saturation current (Is1).