If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #4266
Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874
Hi This might be a basic question, but if one plate of a capacitor was connected to +10kv supply, and the other side connected to a -30kv supply, would the +10kv side increase in voltage to +15kv or +30kv, or stay at +10kv.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
You are talking about matters of potential difference here - difference related to a something which is normally taken to mean Earth.
Therefore, if you have one plate of your capacitor that is at 10 kV relative to Earth, and the other plate has a voltage of -30 Kv relative to Earth upon it, then the potential difference between them is 40 kV.
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600
A metal surface is an isopotential for DC. so it stays at 10kv.
To achieve that, current necessarily flows in from the power supply to do that though; so if you unplug it, and then charge the other plate it will of course vary.
Registered Member #4266
Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874
@Proud Mary You didn't really answer the question, or I expanied it wrong...But will the 10kv one rise to +20kv, if its half of 40kv. If I have two transformers with one supplying one plate to 10kv, and I raise the other plate higher and higher, will the electric field of the 10kv plate increase to 20kv or stay at 10kv to earth?
@BigBad Why would you have to unplug the source? If I had +10kv and -10kv and then raised the -10kv to -30kv, with the transformer(at dc) still connected to the +10kv(not including the return path), your saying that I would have to disconnect the + side transformer for the plate to rise.
Registered Member #8558
Joined: Thu Dec 06 2012, 11:38PM
Location: usa
Posts: 57
No the capacitor does not have to center around 0v. You can have a capacitor with one side grounded and charge the other side to 100v and it wouldn't make ground 50v.
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600
Andy wrote ...
@BigBad Why would you have to unplug the source? If I had +10kv and -10kv and then raised the -10kv to -30kv, with the transformer(at dc) still connected to the +10kv(not including the return path), your saying that I would have to disconnect the + side transformer for the plate to rise.
Any electrically connected metal is going to be at exactly the same DC voltage all over it.
The physics and the reason is that if any charge on the plate or the lead was at a different voltage/potential energy, electrons would immediately move to even out the potential, flee from high voltage potential and attracted to low potential until they're all at the same potential all over. Not the same charge density, you understand, the same potential.
Only if the current can't flow fast enough into or through the plate will the voltage vary across the plate; in the case you're describing nothing is changing nearly fast enough for anything to budge noticeably.
So if you have a power supply with +10kv, and you connect a plate to the 10kv terminal, then the power supply lead and the plate will go to 10kv and be held there by the power supply; and you can wave any charged plates of any voltage (within reason) around near that, and the plate will stay at 10kv.
Some parts of the plate may have more charge than others though, but they will all be at exactly the same potential.
But if you were to charge the plate up to 10kv, and then disconnect it from the power supply, and then (say) move or charge a 30kv plate near to it, the potential on that plate would then change, it would be higher- the same everywhere on the plate, but at higher potential, like 15kv or something. If you put a -30kv plate near it, it would go down 7kv or something.
But it would only do that if it was disconnected from the power supply.
(Actually, I'm talking about metal plates in space, which is a slightly more general question, but two pole capacitors work exactly the same way, air is a dielectric, but you can't change the geometry with a two terminal capacitor.)
Registered Member #4266
Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874
So if you have a power supply with +10kv, and you connect a plate to the 10kv terminal, then the power supply lead and the plate will go to 10kv and be held there by the power supply; and you can wave any charged plates of any voltage (within reason) around near that, and the plate will stay at 10kv.
How high would the charge have to be above reason?
But if you were to charge the plate up to 10kv, and then disconnect it from the power supply, and then (say) move or charge a 30kv plate near to it, the potential on that plate would then change, it would be higher- the same everywhere on the plate, but at higher potential, like 15kv or something. If you put a -30kv plate near it, it would go down 7kv or something.
I don't understand why you would have to remove the supply, but that is what I was thinking about. Isn't 30 kv high than 10kv so more electrons or lack of them will move throught the plate more and raise the voltage, or if minus stop charge going onto the plate.
No the capacitor does not have to center around 0v. You can have a capacitor with one side grounded and charge the other side to 100v and it wouldn't make ground 50v.
But each plate would hold have the voltage wouldn't it, 50% electrons, 50% protons?
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
If you connect a plate to a supply, then you have fixed its voltage. If you change the electric field around it by changing the voltage of a nearby plate, or the position of a nearby charged plate, then charge will flow into or out of the supply along the connecting wire, to maintain the plate at the same supply voltage.
If you have an isolated plate, then you have fixed its charge. If you change the electric field round it, then the voltage of the plate will change.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
I wonder how it would change things to have number of extended plates of small radius arranged parallel to eachother in the form of insulated wires, and all these wires had different voltages on them as in a multi-way cable, or, in a word, a bunch of wires!
Now let's say we just have two parallel wires in a length of electric flex/cord. One of these two insulated wires is connected to the negative pole of a 30V battery, the other terminal of which is earthed. The second wire is connected to the positive terminal of a 10V battery, the other terminal of which is also earthed to a common ground.
Beyond the momentary pulse of current from the batteries as they charge up the capacitance formed between the two insulated wires, does any current flow? No, it doesn't (except for ~picoamp leakage through the insulation, which is not at issue in the present discussion).
Can anything happen at all if one side of each battery is not connected to Earth/chassis common ground? No.
See how folk are bewitched and lose their senses as soon as kilovolts are mentioned!
Registered Member #4266
Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874
I think I understand it. Was planning on building a marx and trying to get the output to feedback into the stages with a transformer supplying the difference. If there is three plates, the middle one +15volt with the left side -15volt the left side is connected in series with the next capacitor and then connected to the right side which is in parallel of the two capacitors.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
10kv and 30kv capactor plates
