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High Voltage and a Crooke's Radiometer

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Nik

Tue Nov 06 2012, 08:01PM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

I had the idea of zapping my Crooke's Radiometer with some HV today to see what king of discharge it would give with such a high vacuum. Not surprisingly there wasn't much more then the scary green "might be x-rays" glow from the glass and a little blueness around the stem. The really interesting part is that it began to spin.

To get my radiometer to spin it takes at least a 100W bulb nearby, a 500W halogen lamp works much better, so I was very surprised to see it spin from the discharge of a violet wand. Does any one have any thoughts as to what the mechanism is for making it spin with HV? I doubt the discharge inside the bulb is enough to heat the vanes of the mill and make it spin for the normal reason.

Here is a video showing both normal and HV operation.

Patrick

Wed Nov 07 2012, 05:34PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

which way does it rotate, like normal radiant heating or counter? what kV are you using?

i have heard some conjecture that ion wind jets can cuase these devices to move outside there normal intended use. Its just the metal pin and vanes are static, so im not sure.

Nik

Wed Nov 07 2012, 08:44PM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

I't rotates in the normal direction, black side trailing. I don't know what voltage is exactly (violet wands don't come with a spec sheet and I don't have an HV scope probe that) but it will jump an inch to ground. More then 5 less then 25kv maybe? The frequency is between 400 and 600hz. Some one else asked me if the vanes might be heated just by the current flowing into and out of the vanes from the gas that surrounds it but I think that would heat both sides of the vanes fairly evenly.

Patrick

Thu Nov 08 2012, 03:04AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

it may be ion jets swirling inside the glass envelope, which then imparts rotation to the vanes. move your HV point tangently across the side of the envelope, see if you can get it to go CCW and then CW...

Nik

Thu Nov 08 2012, 04:33AM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

I took a run down to the lab/laundry room and was unable to get it to spin the other direction. I had it arc to the bulb and a few points along its surface as well as spinning it backwards by shaking it and then turning on the power. In that case it slowed down, stopped and then went the other direction.

Patrick

Thu Nov 08 2012, 05:12AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Nik wrote ...

... spinning it backwards by shaking it and then turning on the power. In that case it slowed down, stopped and then went the other direction.

so it always has the black faces trailing? if so thets compelling, maybe its teh latent heat doing the work from inside the envelope, instead of radiant heat from outside like normel.

PS. im drunk, thAt purple creature is a great friend !!!

Nik

Thu Nov 08 2012, 09:19PM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

The purple tequila monster is one of my very good friends. He and I meet frequently.

The black side is always trailing. I wonder if I could find a way to measure the temperature of the inside of the bulb without putting any holes in it. Maybe If I put an ohmeter on a light bulb then zapped it to see if the resistance of the filament goes up.

Patrick

Thu Nov 08 2012, 11:21PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Nik wrote ...

Maybe If I put an ohmeter on a light bulb then zapped it to see if the resistance of the filament goes up.

this is an excellent idea, just dont go exposing your self to Xrays!

Nik

Sat Nov 10 2012, 05:14PM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

I talked to an other youtube user who has a radiometer with electrodes in it to do exactly what I was observing. They are at the top and bottom so that the electron flow is perpendicular to the rotation and wont spin it like a water wheel. He says the heat produced by electrons bombarding the vanes is enough to cause it to run in the conventional way. Mystery solved!

Patrick

Sat Nov 10 2012, 06:26PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

wow ! that cool to know! so vertically moving electrons cuase no motion, yet your sideways ones must be thermallized of the black surface, giving an always black trailing rotation... Cool!

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