Kapanadze and other FE discussion

[stivep]

Cathode: This is the electrode that is heated and emits the electrons.
Anode:
This electrode in the vacuum tube or valve has a high potential to attract electrons from the cathode.
Grid: This is the valve electrode that has a variable potential and is used to control the flow of electrons between cathode and anode.
https://www.electronics-notes.com/articles/electronic_components/valves-tubes/what-is-a-tube-basics-tutorial.php

Wesley

[kolbacict]

no no. I connect no voltage to any electrode. Just warm the cathode and measure the voltage between the cathode and anode with a voltmeter.
Edison has nothing to do with it. 

[stivep]

Anode:Target area: area of anodes struck by cathode electrons also called (focal track)
• Tube Current: number electrons flowing
from cathode to anode kVp
- on exposure
- measured in mA (milliamperes)

• Filament current: 3-6 A (amperes)
- mAs = number filament electrons
boiled off x time filament heated

When  you have   cathode at right temperature and no other voltage connected  than cloud  of electrons is  moving   to colder  area
or away  from the  filament.
only  when you connect any  measurement tool you have current   flowing by means of closed circuit  by that  device.
Internal  impedance of your  V meter  is determining current flow  and only
now when  you have  current  flow you have    potential difference.
Rather you  must have potential difference first or at the same time 

A potential difference is the energy per unit charge in an electrical circuit.
Potential difference must be measured between two points because it is generally impractical to measure the electrical potential of a single point. ...
Potential difference is commonly known as voltage because volts are the standard unit of measure for this quantity. It is also known historically as pressure and tension.

http://www.wisegeek.com/what-is-a-potential-difference.htm
https://en.wikipedia.org/wiki/Hot_cathode
Wesley

[kolbacict]

Well, here's a volt-ampere characteristic.
8mka-0.7v.
20mka-0.6v.
30mka-0.5v.
60mka-0.45v.
100mka-0.4v.
200mka-0.35v.
500mka-0.25v.
600mka-0.2v.
with load resistance 10mOhm
the voltage at the electrodes reaches 3v. !

[stivep]

That is correct the higher the impedance( resistance) -  the higher is  the potential  difference  -  the  lower is the current.
However Power  dissipated on the load ( your meter)is the same.

Ohms law  for resistance instead  of impedance:
U= R x I


Wesley