Nikola Tesla's Observation of Vacuum Electricity

[lufc88]

Nikola Tesla observed that electrons transmitted through a near perfect vacuum in his vacuum tubes appeared as corona several feet through the air surrounding the tube. He thought that if there is nothing in the tube between the electrode and the glass then how do the electrons convey through the vacuum and into the surrounding air.

 

[JaredJames]

Are you asking how an electron travels through a vacuum?

 

[lufc88]

no electricity

 

[JaredJames]

What do you think electricity is?

An electric current is the movement of charge.

http://en.wikipedia.org/wiki/Electric_charge

You don't need a medium for a charge to flow through.

 

[lufc88]

i thought electricity could not travel in a vacuum

 

[JaredJames]

i thought electricity could not travel in a vacuum

Old CRT televisions use electron beams, fired through the tube which is under vacuum in order to produce a picture.

Your question is the basis for the workings of a Cathode Ray Tube.

Perhaps the wording is ambiguous, the electrons have no medium to 'flow through' in a vacuum. However, they can travel through it.

 

[lufc88]

so then a corona does not need a electric current only the electrons to travel to the end of the tube

 

[AlephZero]

Nikola Tesla observed that electrons transmitted through a near perfect vacuum in his vacuum tubes appeared as corona several feet through the air surrounding the tube.

Did he really "observe" that? Or did he just do some experiment with electrons in a vacuum tube, and observed a corona, but he didn't actually know the corona "consisted of electrons".

There isn't time here to try and make sense of all Tesla's observations (or even find out what he actually observed, as opposed to what a million and one woo-woo websites say he observed). But electric currents create electric and magnetic fields, EM fields can propagate through most materials including glass and air, and they can create coronas when they interact with some gases including air. So there's probably no big mystery here, just somebody jumping to the wrong conclusion.

 

[lufc88]

I don't know it was off a dodgy website so I will look for a more reliable source

 

[lufc88]

http://www.rastko.rs/projekti/tesla/delo/10761
My principal argument is the following: I have experimentally proved that if the same discharge which is barely sufficient to excite a luminous band in the bulb when passed through the primary circuit be so directed as to exalt the electrostatic inductive effect — namely, by converting upwards — an exhausted tube, devoid of electrodes, may be excited at a distance of several feet.

In support of my view I will describe a few experiments made by me. To excite luminosity in the tube it is not absolutely necessary that the conductor should be closed. For instance, if an ordinary exhausted tube (preferably of large diameter) be surrounded by a spiral of thick copper wire serving as the primary, a feebly luminous spiral may be induced in the tube, roughly shown in Fig. 3. In one of these experiments a curious phenomenon was observed; namely, two intensely luminous circles, each of them close to a turn of the primary spiral, were formed inside of the tube, and I attributed this phenomenon to the .existence of nodes on the primary. The circles were connected by a faint luminous spiral parallel to the primary and in close proximity to it. To produce this effect I have found it necessary to strain the jar to the utmost. The turns of the spiral tend to close and form circles, but this, of course, would be expected, and does not necessarily indicate an electro-magnetic effect; whereas the fact that a glow can be produced along the primary in the form of an open spiral argues for an electrostatic effect.

So how is a luminous spiral and a luminous circle induced in a vacuum tube when a copper wire surrounds it?

 

[Drakkith]

Just to throw out a guess, it looks to me like the electrons are inducing a current in the wire which produces a magnetic field that influences the shape and whatnot of the electrons themselves.

 

[alxm]

so then a corona does not need a electric current only the electrons to travel to the end of the tube

That's a self-contradiction. Electric current is the motion of charged particles.

Edit: Also, those writings you're referencing are from 1891, before electrons were discovered.
Prior to that, people thought that electricity was a kind of 'fluid' inside or intrinsic-to matter. In that perspective, it's strange that electricity would be able to flow through a vacuum. But since the discovery of the electron, this has not been a mystery any more than how an apple could fall through a vacuum under the influence of a gravitational field rather than an electric one.

 

[lufc88]

thanks every one
so it is incorrect to say the vacuum is a good conductor of electricity even thought there would be no resistance to the flow?

 

[JaredJames]

thanks every one
so it is incorrect to say the vacuum is a good conductor of electricity even thought there would be no resistance to the flow?

A vacuum is a brilliant insulator. Current doesn't flow through a vacuum, there's nothing for it to flow through.

If you have an anode and cathode in a vacuum, you need to create a PD large enough to force the electrons to 'jump' between them.

 

[Dmytry]

A 'vacuum' is neither a conductor nor insulator. It acts a lot like semiconductor with no doping. If you put charge carriers into vacuum (electrons, or ions), the charge carriers can move through the empty space, conducting the electricity. If you don't put charge carriers into vacuum, there's no charge carriers and current does not flow.

In the insulator such as glass, charge carriers cannot move even if introduced. In the conductor, freely moveable charge carriers are present and can move. In the pure un-doped semiconductor, charge carriers are absent, but externally introduced charge carriers can move. The similarity doesn't end here. Even technological usage is similar. The field effect transistors are in many ways directly analogous to vacuum tubes. You can create 'depletion region' in semiconductor, which acts as insulator. You can create negative electric potential in vacuum, which will repel the electrons (so they won't fly in there).

Behaviour of insulators, conductors, and semiconductors is a lot more complicated than behaviour of vacuum, and it does not explain anything about vacuum to say that vacuum is either of those more complicated things.

 

[Naty1]

"so it is incorrect to say the vacuum is a good conductor of electricity even thought there would be no resistance to the flow?

"

yes it is incorrect...a vacuum is a good insulator.

There are a number of different electrical discharge mechanisms.

http://en.wikipedia.org/wiki/Electric_spark

Air is a good insulator up maybe 10,000 volts or so with small gaps...

http://en.wikipedia.org/wiki/Electric_discharge


If interested, also see discussions on lightning...and associated "leaders".