to hold a negative electric charge at the surface.
Thermion dance
A metallic surface in a vacuum
is half metal, half vacuum, and dancing
dancing on that surface, dance thermions.
When the surface gets too hot
thermions cannot stay on, and so they slip,
they slip into the vacuum like dust motes.
Thermions slip like drops of mist, float
into space, drift like helpless mosquitoes,
and fly like tiny moths attracted to a lamp.
The work function of a surface is the energy that an electron needs
to escape into space. For a metal, this energy varies for
different arrangements of atoms on crystal faces.
Once an electron is free, it can be accelerated by an electric field
toward the anode of a vacuum tube.
John Ambrose Fleming created the first thermionic vacuum tube, the Fleming valve.
Guthrie was a mentor to Fleming
but Fleming was more inspired by the Edison effect
embodied in vacuum tubes.
The work function of a surface is the energy that an electron needs to escape into space. For a metal, this energy varies for different arrangements of atoms on crystal faces. Once an electron is free, it can be accelerated by an electric field toward the anode of a vacuum tube.
John Ambrose Fleming created the first thermionic vacuum tube, the Fleming valve. Guthrie was a mentor to Fleming but Fleming was more inspired by the Edison effect embodied in vacuum tubes.
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