Magnet Myths and Misconceptions

[MileHigh]

"The electrons leave the hot cathode"

Hello Milehigh and TK,

If I recall correctly, I think that the cathode was usually "painted" with a chemical that had a rich supply of electrons available, that when heated with the filament, the electrons would be free to boil on the cathode.  This allowed the tube to have electrons to flow with the high voltage potential of the grid and screens and eventually the plate.

Liberty

There is no such thing as a "chemical with a rich supply of electrons available."   The cathode is effectively two things at the sane time.  It is the secondary load of a transformer, that's how it heats up.  This is completely isolated from the main circuit which is the second component.  The main circuit pumps electrons through the cathode such that they end up striking the phosphor screen.  The main circuit is the source of the electrons.  The main circuit is not even "aware" that the cathode is also a load resistor for the secondary of a transformer.

The heat facilitates the liberation of the electrons, somewhat akin to heating water facilitates the more rapid evaporation of the water.

[Liberty]

There is no such thing as a "chemical with a rich supply of electrons available."   The cathode is effectively two things at the sane time.  It is the secondary load of a transformer, that's how it heats up.  This is completely isolated from the main circuit which is the second component.  The main circuit pumps electrons through the cathode such that they end up striking the phosphor screen.  The main circuit is the source of the electrons.  The main circuit is not even "aware" that the cathode is also a load resistor for the secondary of a transformer.

The heat facilitates the liberation of the electrons, somewhat akin to heating water facilitates the more rapid evaporation of the water.

Some tubes use an electrically separate cathode that is heated up by the filament.  Some tubes use the filament itself as the cathode. 

[Liberty]

There is no such thing as a "chemical with a rich supply of electrons available."   The cathode is effectively two things at the sane time.  It is the secondary load of a transformer, that's how it heats up.  This is completely isolated from the main circuit which is the second component.  The main circuit pumps electrons through the cathode such that they end up striking the phosphor screen.  The main circuit is the source of the electrons.  The main circuit is not even "aware" that the cathode is also a load resistor for the secondary of a transformer.

The heat facilitates the liberation of the electrons, somewhat akin to heating water facilitates the more rapid evaporation of the water.

I was taught that the manufactures use a chemical on the cathode.  If they don't, how does a tube wear out or get weak?  Tubes do become weak performers after a time, as there are tube testers to check their operation.  I always thought that it was because the chemical coating on the cathode eventually wore out after a while due to the heat of the filament.  Or not?

[MileHigh]

You may be right that there is a chemical coating on the cathode that facilitates the liberation of the electrons.  I honestly don't know.  When I read what you say I am wondering if a substance can act as a sort of catalyst for the liberation of the electrons.  But to be clear, "facilitating" is definitely not being a source of electrons.

For testing tubes, the filament can simply burn out like a light bulb.  I am guessing that that happens less frequently then the other failure mode.  That mode being when the tube loses its partial vacuum.  If the tube leaks and air enters, that will block the transmission of the electrons because they need a rarefied partial vacuum medium.

There are probably other failure modes.  I am old enough to remember tube testers being at the local pharmacy!  lol

It's scary to think that soon there will be adults that never saw CRT-based TVs for sale at Big Box stores, and adults that never walked into a video club to rent a movie!

MileHigh

[CANGAS]

Cangas:

I disagree strongly.  Hopefully this new example will swat this nonsensical belief in literal "lines" or "threads" of magnetic field.  There are NO LINES.  The lines are there ONLY to help you visualize the strength and direction of the magnetic field, and that's all.

Look at the attached diagram.  Do you think that there are real "lines" in the air?  What is your common sense telling you?  Now apply that common sense to magnetic fields.

You can't prove that there aren't pink elephants floating over the sky in the center of Greenland either, but you can use your common sense and not let yourself get led down a garden path because you see lines used as a visual aid in diagrams.

MileHigh

u speed reed dont u

It has been proven that speed readers miss over 90% of the content of the stuff they have fleetingly skimmed over. You have ran that up to either 99% or 100%.

My post blatantly stated that FIELD LINES are a useful MODEL.

My post blatantly stated that FIELD LINES may or may not be real, and cannot be proved to either exist or to not exist per se.

Just what is it that you disagree  with me about?

Do you know, or, do you just try to be disagreeable at any opportunity?


CANGAS 87