Vacuum Diode: Thermionic Emission and Half‑Wave Rectification

The simulation models a vacuum diode where a heated filament (cathode) emits electrons through thermionic emission. As the filament temperature rises, more electrons are released, creating a space‑charge cloud that limits the current until saturation is reached. The device can also be used as a half‑wave rectifier, converting an AC input into a pulsed DC output.

Students can select from several preset experiments and then vary key parameters with sliders and input fields: filament temperature, plate (anode) voltage or AC drive, load resistance, and a smoothing capacitor. Additional controls allow reversal of the plate supply, sweeping of the plate voltage, and clearing or pausing the plotted data. The graph displays current‑voltage characteristics and rectified waveforms, updating in real time as parameters change.

By interacting with the model, learners observe how temperature influences emission current (Richardson‑Dushman law), how space‑charge limits current (Child‑Langmuir law), and how diode polarity and load affect rectification efficiency. The activity reinforces concepts in current electricity, electronic device operation, and basic signal processing.