The instrumentation that they used was inadequate to draw relevant conclusions.
For a 9V battery to short-circuit, we have to get the breakdown voltage below 9V per the gap between the electrodes. The gap is .22 inches, or 0.005588 m. So that's 9 V / 0.005588 m = 1610.59413028 V/m.
STP air, at 1013.25 millibars, has a breakdown voltage of 3,000,000 V/m.
Since resistance varies directly with pressure, to drop the breakdown voltage, we have to drop the pressure to a fraction of STP air equal to the fraction of target voltage over the STP voltage. So that's 1610.59413028 / 3,000,000 = 0.00053686471, which we multiply by 1013.25 millibars to get a target pressure of 0.5439781674 millibars.
So they reported:
Our Safeway 9V battery survived the test with no apparent harm. During the test, the vacuum gauge registered a full 30 inches of mercury (762 mm Hg). This represents a full vacuum, within the limits of gauge accuracy.
An inch of mercury = 33.86 millibars, so they got a pressure deficit of 30 * 33.86 = 1015.8 millibars. Wait a second — STP air is 1013.25 millibars. No, they didn't get a pressure deficit that created an absolute pressure that was below zero!!!
If we look at the photo that they took of the gauge...
...I'd say that it was actually reading 29.4 inches of mercury, which would mean a pressure deficit of 29.4 * 33.86 = 995.484 millibars. That subtracted from STP (1013.25) = 17.766 millibars. And remember that we were looking for a pressure below 0.5439781674 millibars to get a short-circuit. So if that's correct, no short-circuit would be expected. But obviously these numbers are all over the place, and we can't do anything with these.
BTW, the pressure in space is 0.00032 millibars, at 100 km above the surface.
upriver
Re: Does Space Insulate or Conduct?
Lloyd wrote: Thanks a lot, David. Looks like a good test. And your related comments sound very relevant as well.
Something doesn't seem to be adding up now. If the rocket tests showed increasing conductance with decreasing atmospheric pressure, it seems that the vacuum should have the most conductance. But if batteries don't short out in vacuum, it seems that vacuum must have low conductance.
Seems to be a paradox. And paradoxes mean opportunities.
There is this pesky little thing called work function which determines how easily electrons leave the cathode. You have to either heat the cathode or turn up the voltage.
Thats what you are seeing with the 9v battery experiment.
From wiki.... "A cathode electrode in a vacuum tube or other vacuum system is a metal surface which emits electrons into the evacuated space of the tube. Since the negatively charged electrons are attracted to the positive nuclei of the metal atoms, they normally stay inside the metal, and require energy to leave it.[1] This energy is called the work function of the metal.[1] In a hot cathode, the cathode surface is induced to emit electrons by heating it with a filament, a thin wire of refractory metal like tungsten with current flowing through it.[1][2] The increased thermal motion of the metal atoms knocks electrons out of the surface; this process is called thermionic emission.[1]
There are two types of hot cathodes:[1]
Directly heated cathode: In this type, the filament itself is the cathode and emits the electrons directly. Directly heated cathodes were used in the first vacuum tubes. Today they are used in fluorescent tubes and most high power transmitting vacuum tubes. Indirectly heated cathode: In this type, the filament is not the cathode but rather heats a separate cathode consisting of a sheet metal cylinder surrounding the filament which then emits electrons. Indirectly heated cathodes are used in most low power vacuum tubes. For example, in most vacuum tubes the cathode is a nickel tube heated by a tungsten filament inside it, and the heat from the filament causes the outside surface of the tube to emit electrons.[2] The filament of an indirectly-heated cathode is usually called the heater. The main reason for using an indirectly heated cathode is to isolate the rest of the vacuum tube from the electric potential across the filament. Many vacuum tubes use alternating current to heat the filament. In a tube in which the filament itself was the cathode, the alternating electric field from the filament surface would affect the movement of the electrons and introduce hum into the tube output. It also allows the filaments in all the tubes in an electronic device to be tied together and supplied from the same current source, even though the cathodes they heat may be at different potentials.
Glow of a directly-heated cathode in an Eimac 4-1000A 1 kW power triode tube in a radio transmitter. Directly heated cathodes operate at higher temperatures and produce a brighter glow. The cathode is behind the other tube elements and not directly visible. In order to improve electron emission, cathodes are usually treated with chemicals, compounds of metals with a low work function. These form a metal layer on the surface which emits more electrons. Treated cathodes require less surface area, lower temperatures and less power to supply the same cathode current. The untreated tungsten filaments used in early vacuum tubes (called "bright emitters") had to be heated to (1400°C), white-hot, to produce sufficient thermionic emission for use, while modern coated cathodes produce far more electrons at a given temperature so they only have to be heated to 800 (425-600°C)[1][3][4]"
Brant
David
Re: Does Space Insulate or Conduct?
upriver wrote:
There is this pesky little thing called work function which determines how easily electrons leave the cathode. You have to either heat the cathode or turn up the voltage.
That's right. And as someone already mentioned earlier, the vacuum has a dielectric strength of 1012 MV/m.
The batteries used by NASA have voltages which are many orders of magnitude below the breakdown voltage.
upriver wrote: There is this pesky little thing called work function which determines how easily electrons leave the cathode. You have to either heat the cathode or turn up the voltage.
That's right. And as someone already mentioned earlier, the vacuum has a dielectric strength of 1012 MV/m.
The batteries used by NASA have voltages which are many orders of magnitude below the breakdown voltage.
No, the vacuum does not have a dielectric strength of 1012 MV/m. It has a dielectric strength of 0 V/m, if you can assign a resistance to nothingness. But Brant is right that the work function also comes into play — in addition to overpowering the resistance (if any) in the medium between the electrodes, you also have to break the electrons out of the covalent bonds in the crystal lattice so that they can begin their trek through the medium to the other electrode. In our case, we'd have to demonstrate that the pressure had been dropped below 0.54 millibars, and that the ionization potential of the electrode wasn't getting in the way.
Maol
Re: Does Space Insulate or Conduct?
Electromagnetic fluctuation forces across plasmas analogous to so-called weak nuclear interaction forces
In addition to overpowering the resistance (if any) in the medium between the electrodes, you also have to break the electrons out of the covalent bonds in the crystal lattice so that they can begin their trek through the medium to the other electrode.
That's exactly what the dielectric strength tells you; the voltage necessary to break the electrons out of their covalent bonds and then pass through the insulator (for example, rubber).
The numbers below were derived experimentally, by applying voltages to a DC circuit. Dielectric strength is the applied voltage divided by the electrode separation (the insulated gap in the circuit). The numbers represent the voltage at which breakdown occurs, allowing electrons to flow through the insulating material.
The dielectric strength of air is 3 MV/m.
The dielectric strength of rubber is 20 MV/m.
The dielectric strength of vacuum is 1012 MV/m.
As you can clearly see, vacuum has far and away the highest dielectric strength of any material; that is, its ability to resist the flow of current in a DC circuit. It requires enormous voltages to get current to flow across a vacuum insulated gap in a circuit.
CharlesChandler
Re: Does Space Insulate or Conduct?
David wrote: The dielectric strength of vacuum is 1012 MV/m.
As you can clearly see, vacuum has far and away the highest dielectric strength of any material; that is, its ability to resist the flow of current in a DC circuit. It requires enormous voltages to get current to flow across a vacuum insulated gap in a circuit.
How was that determined? If you're going on the basis of the Paschen curve, that's another thing that has been grossly misinterpreted. With decreasing distance between electrodes, and/or decreasing pressure in the medium separating them, it takes more and more volts to get an arc discharge. This is interpreted as a measure of the resistance, but that's incorrect. Same electrodes, same medium, same temperature, shorter distance, greater resistance? No. Nothing in the electrodes changed, and nothing in the medium changed, so the resistance of those entities did not change. What changed was that you got the electrodes close enough together that there just isn't enough resistor between the electrodes to manifest any sort of breakdown, and the current happily flowed in glow or dark mode, without there being a spark. But this doesn't mean that no current was flowing, because the resistance went through the roof. Remember that R = V/I. If you actually want to measure the resistance, you have to judge it by the volts and the current (using an ammeter), not by whether or not you got a spark.
De omnibus dubitandum est.
David
Re: Does Space Insulate or Conduct?
CharlesChandler wrote:
What changed was that you got the electrodes close enough together that there just isn't enough resistor between the electrodes to manifest any sort of breakdown, and the current happily flowed in glow or dark mode, without there being a spark. But this doesn't mean that no current was flowing, because the resistance went through the roof. Remember that R = V/I. If you actually want to measure the resistance, you have to judge it by the volts and the current (using an ammeter), not by whether or not you got a spark.
If the current "happily flowed", as you put, then the copper wire in the circuit would be instantly vaporized at those high levels of voltage. If you apply a million volts to a circuit, the resistance better be very high; otherwise you best run for cover and say a prayer.
JeffreyW
Re: Does Space Insulate or Conduct?
David wrote:
CharlesChandler wrote:
In addition to overpowering the resistance (if any) in the medium between the electrodes, you also have to break the electrons out of the covalent bonds in the crystal lattice so that they can begin their trek through the medium to the other electrode.
That's exactly what the dielectric strength tells you; the voltage necessary to break the electrons out of their covalent bonds and then pass through the insulator (for example, rubber).
The numbers below were derived experimentally, by applying voltages to a DC circuit. Dielectric strength is the applied voltage divided by the electrode separation (the insulated gap in the circuit). The numbers represent the voltage at which breakdown occurs, allowing electrons to flow through the insulating material.
The dielectric strength of air is 3 MV/m.
The dielectric strength of rubber is 20 MV/m.
The dielectric strength of vacuum is 1012 MV/m.
As you can clearly see, vacuum has far and away the highest dielectric strength of any material; that is, its ability to resist the flow of current in a DC circuit. It requires enormous voltages to get current to flow across a vacuum insulated gap in a circuit.
This is why the Sun being powered by an external circuit is completely strange. It is like the Sun is completely engulfed by a giant transparent rubber ball.
Or like saying rubber tubing, not copper wire, works better to conduct electricity in disconnects and panel boards. Strange.
Saying the Sun is like a node in a giant electrical grid completely ignores the fact that vacuum has been experimentally verified to be highly electrically insulating, meaning electric current as electrical conduction does NOT flow out of, or into the Sun.
Plasma does conduct electricity, but outer space is vacuum. The Sun is comprised of plasma and charged particles are coming out of it, but this is because of heterolytic cleavage. The neutral particles split during electrolysis into negative and positive components. In other words, it is chemistry and does not require insulating electrical grids (a contradiction).
Sparky
Re: Does Space Insulate or Conduct?
Saying the Sun is like a node in a giant electrical grid completely ignores the fact that vacuum has been experimentally verified to be highly electrically insulating,
And you are ignoring the fact that the solar wind is current. So, everywhere there are ions in the vacuum of space, those ions promote current.
CharlesChandler
Re: Does Space Insulate or Conduct?
David wrote: If the current "happily flowed", as you put, then the copper wire in the circuit would be instantly vaporized at those high levels of voltage. If you apply a million volts to a circuit, the resistance better be very high; otherwise you best run for cover and say a prayer.
Volts never vaporized anything. It's the amps that do the damage. And yes, in a short-circuit, you find out the current-carrying capacity of the weakest link in the circuit.
I'll never forget the time that I was walking across the factory floor to get back to my office, and that entire section of the factory lit up in bright blue light. And there was this really loud "pop!". I turned around and saw the maintenance supervisor standing in front of the main electrical panel for the entire plant, looking a bit dazed. He had figured out how to short several hundred amps by letting his screwdriver touch the frame, as he tightened a loose screw on the main board. The arc took a big bite out of the shaft of the screwdriver, and the frame. But it happened so fast that the mains didn't even kick out. The screw soldered itself tight, so it was OK.
upriver
Re: Does Space Insulate or Conduct?
I think there is still some confusion about the motion of a particle through space. No resistance. A bunch of these particles are called electricity. Kinetic energy does the work. Think of a photon. It has no mass but it can do work by virtue of its kinetic motion.
When you measure the "breakdown of space or vacuum" you are not measuring the breakdown of vacuum.
You are measuring the properties of the matter that emits the electrons.
I would almost go so far as to say kinetic energy is the aether that is "received by the shape of the sun" and converted into energy attached to electrons to do work.
Brant
viscount aero
Re: Does Space Insulate or Conduct?
It's interesting to see in this thread how people can have entirely different perceptions of outer space. Some think it is an insulator. Whereas others think it is a conductor--completely and totally the opposite condition And some, like, me are skeptical of either assessment. Paradoxically, space is the "largest thing" out there. And yet it is not clearly defined as being anything!
upriver
Re: Does Space Insulate or Conduct?
viscount aero wrote: It's interesting to see in this thread how people can have entirely different perceptions of outer space. Some think it is an insulator. Whereas others think it is a conductor--completely and totally the opposite condition And some, like, me are skeptical of either assessment. Paradoxically, space is the "largest thing" out there. And yet it is not clearly defined as being anything!
Because nobody has defined what electricity really is...
JeffreyW
Re: Does Space Insulate or Conduct?
viscount aero wrote: It's interesting to see in this thread how people can have entirely different perceptions of outer space. Some think it is an insulator. Whereas others think it is a conductor--completely and totally the opposite condition And some, like, me are skeptical of either assessment. Paradoxically, space is the "largest thing" out there. And yet it is not clearly defined as being anything!
Well if it were a conductor then if an astronaut tossed a 9V battery out the window of the ISS, it should explode from constant short circuiting, exactly as if you tied together the poles of the battery with a copper wire.
The answer to the question is "vacuum" does not conduct electric current, because there is no matter to do the conducting.
Same with heat. There is no heat conduction in vacuum because there is no matter!
Saying there is electrical conduction in vacuum is like saying there is heat conduction in vacuum.
I think this entire argument can be chalked up to people confusing radiation with electrical conduction. There being no resistance to radiation in vacuum is not the same as no resistance to electrical conduction. They are two completely different animals.
But Brant is right that the work function also comes into play — in addition to overpowering the resistance (if any) in the medium between the electrodes, you also have to break the electrons out of the covalent bonds in the crystal lattice so that they can begin their trek through the medium to the other electrode. In our case, we'd have to demonstrate that the pressure had been dropped below 0.54 millibars, and that the ionization potential of the electrode wasn't getting in the way.
And some, like, me are skeptical of either assessment. Paradoxically, space is the "largest thing" out there. And yet it is not clearly defined as being anything!
