Can activated carbon be used to create a high voltage DC electroscope?

In summary: I don't know. I need to find something that is both very resistive and non-conductive. I guess some sort of polymer would work? The device you describe sounds like a Wimshurst machine. These generate a good spark and it is DC at about 50000 volts. You have to wind a handle to get the voltage.The next step up would be a Van Der Graaf machine, but that may be too high a voltage for your project. Good ones generate sparks that are a foot long, or more.Another choice, at your own risk, is a defunct color TV set which has a source of 30000 volts DC in it. If this part of the circuit was still working,
  • #1
taylaron
Gold Member
397
1
Happy holidays everyone!

I'm searching how to produce high voltage, high current DC electricity to be used for statically charging a giant electroscope. The explanation why is very elaborate, so to put it simply, I need to energize a giant electroscope.

I have limited electrical engineering education, but a thorough explanation would be appreciated.

Perhaps using a Telsa coil to generate high voltage AC current and then rectify the current. Evidently this is not an option because rectifying circuits can not handle such extreme voltages.

Any Ideas?

Regards,
-Tay
 
Engineering news on Phys.org
  • #2
Probably a Wimshurst Machine would be OK. These generate a good spark and it is DC at about 50000 volts. You have to wind a handle to get the voltage.

The next step up would be a Van Der Graaf machine, but that may be too high a voltage for your project. Good ones generate sparks that are a foot long, or more.

Another choice, at your own risk, is a defunct color TV set which has a source of 30000 volts DC in it. If this part of the circuit was still working, that would be plenty for an electroscope.

For you and anyone else reading this, be aware that any voltage over 50 volts can kill you, especially if it is on a capacitor capable of delivering a lot of current.

Don't operate Van Der Graaf machines anywhere near electronic equipment.
 
  • #3
How giant is that electroscope?
There is a giant Van de Graaff generator that should be perfect for charging giant things.
http://www.mos.org/sln/toe/
However I don't think they will borrow it to you.
 
  • #4
I'm attempting to energize 10 grams of activated carbon to the highest static potential possible. I will then use the discharge to power a circuit, regulating the flow of electricity with a "current potentiometer" I designed. The surface area is calculated using the activated carbon surface area to weight ratio of 100m^2 per gram [Figure from http://www.cee.vt.edu/ewr/environmental/teach/wtprimer/carbon/sketcarb.html] . Imagine an electroscope with 1,000 m^2 of surface area made of conductive carbon...
 
Last edited by a moderator:
  • #5
That link doesn't seem to be working, but maybe you could explain why you think this would be a good idea?

One key to getting a high voltage onto something without it discharging is to have a very smooth surface. Charge tends to spark away at any sharp point.
So, you always see Van Der Graaff generators with a highly polished dome on them.

I have to wonder if your conductive carbon would act like a lot of sharp points.

What circuit are you thinking of powering after your "current potentiometer". I'm not even sure what that is, so you could explain that, too, if you like.
 
  • #6
vk6kro said:
That link doesn't seem to be working
http://www.cee.vt.edu/ewr/environmen...sketcarb.html"
The OP has an extra ] at the end.
 
Last edited by a moderator:
  • #7
This one works:

http://www.cee.vt.edu/ewr/environmental/teach/wtprimer/carbon/sketcarb.html
 
Last edited by a moderator:
  • #8
I apologize for the broken link and yes, http://www.cee.vt.edu/ewr/environmental/teach/wtprimer/carbon/sketcarb.html is the correct link.

The device I'm describing is similar to modern super capacitors according to http://scitizen.com/screens/blogPage/viewBlog/sw_viewBlog.php?idTheme=5&idContribution=174

an appropriate diagram of a modern super capacitor cell can be found here:
http://www.nanomac.uq.edu.au/pdfs/Fact%20SheetSupercapicitors.pdf

Instead of having multiple cells in a super capacitor, I'm attempting to merge the layers into one block and provide a more compact, powerful version. I realize that combining the cells eliminates the possibility of putting multiple cells in series or parallel and thus dramatically increases the discharge voltage (if I am correct).
To prevent premature discharge, the activated carbon would be placed in a very resistive dielectric container.

To best illustrate the device and DC circuit I intend to build, think of two classic gold foil electroscopes, each discharge probe spaced apart from one another. One of the electroscopes is charged with static electricity and the other is neutral. Between the charged scope and the circuit is a "current potentiometer or c-pot". After the c-pot is a resistor and then the resistor is connected to the neutral electroscope. This is illustrated in the image attached. The electrons flow from the high concentration in one electroscope to the other neutral electroscope until both scopes have reached static equilibrium.

I realize that the definition of a circuit is along the lines of 'current traveling in a closed loop' and that the "circuit" described above doesn't exactly describe this definition. But for simplicity sake, I will continue to use the word circuit, although it is the wrong term.

The c-pot I describe works by varying the conductivity of a material. Unfortunately I intend to patent the concept so I can not give much detail.

I am concerned that the electrons stored on the surface area of the activated carbon will not be able to travel freely within the body of activated carbon itself and reach the conductive terminal on one end. Activated carbon supposedly is conductive, but can charge on one side of a clump freely move to the other side? I sure as heck hope so, because modern super capacitors do it on a smaller scale. The increased thickness concerns me.

The dielectric containing the activated carbon would of course be filled with a liquid. Can the liquid be conductive and still be able to store electrons on the surface of the activated carbon?

According to http://www.theactivatedcarbon.com/page/activated-carbon-properties/" 10 grams of activated carbon would provide 15,000m^2 of surface area to store electrons on.
Thoughts?

Thank you for your help

-Tay
 

Attachments

  • electroscope_circuit_2.jpg
    electroscope_circuit_2.jpg
    14.5 KB · Views: 458
Last edited by a moderator:
  • #9
Your c-pot sounds like a simple transistor.
If you statically charge a piece of activated carbon, it won't store much more charge then an equally big sphere.
In a super capacitor the large surface area gives you a large capacitance, however if you just put that activated carbon into an insulating liquid and apply a charge to it you don't get a capacitor effect. The capacity will be very small. The charge will not distribute over the entire surface area. It will only be at the outside. All the surface area on the inside will stay free of charge.
To get a large capacitance the carbon needs to be in a conductive liquid. But then you can only apply a small voltage.
 

Related to Can activated carbon be used to create a high voltage DC electroscope?

What is High Voltage Direct Current (HVDC)?

High Voltage Direct Current (HVDC) is an electrical transmission system that is used to transmit electricity over long distances at high voltages. It involves the conversion of alternating current (AC) to direct current (DC) and vice versa using power electronic devices.

What are the advantages of using HVDC over traditional AC transmission?

There are several advantages of using HVDC over traditional AC transmission, including lower transmission losses, higher efficiency, and the ability to transmit electricity over longer distances without the need for intermediate substations. HVDC also allows for the interconnection of asynchronous AC systems and the integration of renewable energy sources into the grid.

What are the main components of an HVDC system?

The main components of an HVDC system include converters, transformers, and the transmission line. The converters are responsible for converting AC power to DC power and vice versa. The transformers are used to step up or step down the voltage of the electricity, while the transmission line is used to transmit the high voltage DC electricity over long distances.

How is HVDC used in the real world?

HVDC is used in various applications in the real world, including long-distance power transmission, submarine power cables, and the interconnection of different power grids. It is also used in renewable energy projects, such as offshore wind farms, to transmit electricity to the mainland.

What are the potential drawbacks of using HVDC?

Despite its advantages, there are also potential drawbacks of using HVDC. These include high initial costs, the complex control and protection systems required, and the need for skilled personnel to operate and maintain the system. HVDC also has lower fault current levels, which can make it more difficult to detect and isolate faults in the system.

Similar threads

Replies
1
Views
1K
  • Electrical Engineering
Replies
8
Views
2K
Replies
23
Views
3K
  • Electrical Engineering
Replies
5
Views
3K
  • Electrical Engineering
Replies
14
Views
5K
Replies
13
Views
3K
  • Electrical Engineering
Replies
2
Views
3K
Replies
12
Views
31K
Replies
3
Views
4K
Back
Top