Vacuum Tube Diode Explained: Electron Boiling

[pardesi]

Can anyone explain me the mechanism of vacuum diode.Specifically how the electronts which are 'boiled' of the cathode behave

 

[Meir Achuz]

They leave the cathode at low, thermal velocities.
They are accelerated to the anode by the electric field between the anode and the cathode.

 

[pardesi]

why are there any space charges at all why don'e they flow towards the anode

 

[Meir Achuz]

why are there any space charges at all why don'e they flow towards the anode

The space charge does flow toward the anode, but more electrons keep coming from the cathode, so there is a steady current and a constant space charge.

 

[pardesi]

well actually i was talking about the situation before the steady current begins then what does happen