Timeline for Why does a cathode have to be heated to emit electrons?
Current License: CC BY-SA 3.0
5 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Aug 12, 2013 at 21:02 | vote | accept | yippy_yay | ||
| Aug 12, 2013 at 20:56 | comment | added | user4552 | @SebastianHenckel: No, what matters locally is the electric field. The electric field required in order to cancel the electric field holding the electrons in at the surface is $\sim(5\ \text{V})/(0.1\ \text{nm})$. This is basicallly the strength of the microscopic fields, and if you apply it externally to matter, the matter is destroyed. | |
| Aug 12, 2013 at 20:37 | comment | added | yippy_yay | If the work function is around 5 eV, shouldn't cathodes that have a potential drop to the anode of more than 5V start emitting without heat? | |
| Aug 10, 2013 at 8:31 | comment | added | Vasiliy | In my opinion, very weak explanation. Given that electron feels attractive force once it "finds itself at the surface", it would take him some time to stop and reverse the speed. In this case, we could observe electrons "flying out of material", and these electrons could easily be extracted. Also, the net electric force which affects the electron once it is out of the lattice is very weak due to screening effects. | |
| Aug 10, 2013 at 0:05 | history | answered | user4552 | CC BY-SA 3.0 |