Generation of Large Electrostatic field

[[email protected]]

Hello,

I'm trying to figure out a simple way in which to create a large,
static electric field (at least 10^4 V/m, if not 10^5 or even higher)
over a short distance (about, or less than, 1cm). Could I simply hook
some high voltage source up to a parallel plate type configuration and
put them close together? Obviously if the field is larger than the
dielectric strength of air this would have to be done in vacuum, but
are there any other special considerations for generating large
electric fields? Can this large field be created with "standard"
lab equipment?

 

[srp]

[email protected] a écrit :

Hello,

I'm trying to figure out a simple way in which to create a large,
static electric field (at least 10^4 V/m, if not 10^5 or even higher)
over a short distance (about, or less than, 1cm). Could I simply hook
some high voltage source up to a parallel plate type configuration and
put them close together?
Yes.

Obviously if the field is larger than the
dielectric strength of air this would have to be done in vacuum, but
are there any other special considerations for generating large
electric fields?

The most important is to keep your hands away.

Can this large field be created with "standard"
lab equipment?

Yes.

André Michaud

 

[Don Taylor]

I'm trying to figure out a simple way in which to create a large,
static electric field (at least 10^4 V/m, if not 10^5 or even higher)
over a short distance (about, or less than, 1cm). Could I simply hook
some high voltage source up to a parallel plate type configuration and
put them close together? Obviously if the field is larger than the
dielectric strength of air this would have to be done in vacuum, but
are there any other special considerations for generating large
electric fields? Can this large field be created with "standard"
lab equipment?

Since you have 1cm or less you need only 100, if not only 1000 volts
to generate your 10^4 V/m or 10^5 V/m. 1000 volt dc bench supplies
aren't that hard to buy or build.

Now if you wanted it with the plates separated by 10 meters, then that
would be more challenging And perhaps something for Van De Graff.

 

[Jonathan Thornburg -- remove -animal to reply]

I'm trying to figure out a simple way in which to create a large,
static electric field (at least 10^4 V/m, if not 10^5 or even higher)
over a short distance (about, or less than, 1cm). Could I simply hook
some high voltage source up to a parallel plate type configuration and
put them close together? Obviously if the field is larger than the
dielectric strength of air this would have to be done in vacuum, but
are there any other special considerations for generating large
electric fields? Can this large field be created with "standard"
lab equipment?

You might try re-posting your query over in sci.space.science.
A couple of regular posters there are active participants in space
experiments that involve such equipment.

ciao,

--
-- "Jonathan Thornburg -- remove -animal to reply" <[email protected]>
Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut),
Golm, Germany, "Old Europe" http://www.aei.mpg.de/~jthorn/home.html
"ActiveX as a security component? Isn't that like Ben and Jerry's ice
cream as a diet component?" -- Bill Unruh, sci.crypt, 18.Jul.2003

 

[KC]

Hi,

Try this link:
http://users.pandora.be/educypedia/electronics/electricitytesla.htm#Van de graaf generator

Tesla coils and at the bottom the Van de Graaf generators.

 

[Don Kelly]

----------------------------

Hello,

I'm trying to figure out a simple way in which to create a large,
static electric field (at least 10^4 V/m, if not 10^5 or even higher)
over a short distance (about, or less than, 1cm). Could I simply hook
some high voltage source up to a parallel plate type configuration and
put them close together? Obviously if the field is larger than the
dielectric strength of air this would have to be done in vacuum, but
are there any other special considerations for generating large
electric fields? Can this large field be created with "standard"
lab equipment?

10^5 volts/meter is not a particularly high field. For example, At 1 cm,
and normal temperature and pressure, the breakdown voltage of a 1 cm gap is
about 30KV (doesn't increase linearly with gap width). This is for a uniform
gap - either large plates with radiused edges (to eliminate edge effects),
or, as used in labs, spheres of the order of 20 to 30cm diameter.

Now, if you are going to put something into this field, the breakdown
voltage may be significantly reduced.

However, from the tenor of your question, I strongly suggest that you stay
away from high voltage experimentation until you learn more.

 

[Dave]

sure, no problem. 10^4 v/m is only 100v across 1cm, easy. 10^5 v/m is only
1000v at 1cm, you can get up to about 10,000 v across 1cm of air or 10^6v/m
before it breaks down if its dry and clean. beyond that you need something
better, like a vacuum or some other dielectric material. you should also
have smooth and flat plates, have them bend in a wide radius away from each
others at the ends to limit fringe effects, and lots of safeties and
interlocks. high voltage power supplies are available up to at least 100kv
dc, beyond that it starts to really get expensive.

 

[Tom Roberts]

I'm trying to figure out a simple way in which to create a large,
static electric field (at least 10^4 V/m, if not 10^5 or even higher)

That's not really very large. Wires carrying house current (120 V in the
U.S.) can be stripped and held ~3 mm apart without breaking down the air
(60 Hz ac is essentially dc as far as breakdown is concerned). That's
4*10^4 V/m. A classroom Van De Graff machine generates ~200,000 Volts
over ~0.5 meter, which is 4*10^5 V/m -- in this case ionization of the
air is usually quite apparent.

In modern particle accelerators, gradients of 5 MegaVolts/meter
are common, but this is using RF frequencies, not dc. In tests
we have achieved over 80 MegaVolts/meter (in high pressure
hydrogen gas, using RF at 805 MHz).

over a short distance (about, or less than, 1cm).

10^4 V/m over 1 cm is just 100 Volts. That's easy. Doing 10^5 V/m you'll
need to be sure that all surfaces are smooth (because sharp corners will
ionize the air, and could initiate sparking).

Could I simply hook
some high voltage source up to a parallel plate type configuration and
put them close together? Obviously if the field is larger than the
dielectric strength of air this would have to be done in vacuum, but
are there any other special considerations for generating large
electric fields? Can this large field be created with "standard"
lab equipment?

Plates connected to a lab ~100 Volt power supply and separated by 1 cm
is easy.

Watch your fingers! -- you seem quite unknowledgeable about this sort of
apparatus. I recommend getting someone with experience to assist --
these things can be dangerous.


Tom Roberts [email protected]

 

[Robert Baer]

Hello,

I'm trying to figure out a simple way in which to create a large,
static electric field (at least 10^4 V/m, if not 10^5 or even higher)
over a short distance (about, or less than, 1cm). Could I simply hook
some high voltage source up to a parallel plate type configuration and
put them close together? Obviously if the field is larger than the
dielectric strength of air this would have to be done in vacuum, but
are there any other special considerations for generating large
electric fields? Can this large field be created with "standard"
lab equipment?

Have not done any calculations, but a simple vacuum does not
necessarily add much to dielectric strength.
It probably would arc easily.
So i would suggest an insulator that would do two things for you: 1)
the higher dielectric constant, therby making it easier to get a larger
electric field for a given voltage source, and 2) the possibility of
standing off that much field strength without arcing.

 

[[email protected]]

Have not done any calculations, but a simple vacuum does not
necessarily add much to dielectric strength.

It makes matters worse, in fact, till you get to really good vacuum.
On pumping down from atmospheric pressure to 1 torr dielecetric
strength decreases dramatically and remains quite poor to around
10^(-2)-10^(-3) torr. Then it starts improving but ou have to get to
circa 10^(-5) or so before you get back to atmospheric levels.

Mati Meron | "When you argue with a fool,
[email protected] | chances are he is doing just the same"

 

[nobody home]

[email protected] wrote in

Hello,

I'm trying to figure out a simple way in which to create a
large, static electric field (at least 10^4 V/m, if not 10^5 or
even higher) over a short distance (about, or less than, 1cm).
Could I simply hook some high voltage source up to a parallel
plate type configuration and put them close together? Obviously
if the field is larger than the dielectric strength of air this
would have to be done in vacuum, but are there any other special
considerations for generating large electric fields? Can this
large field be created with "standard" lab equipment?

Take a look at Wimshurst Static Generator,
http://www.powerlabs.org/wimshurst.htm

I made one, go to sunday flea market, buy two 33rpm records.
Buy copper snail tape and tape small 1/2" copper to vinyl record,
spaced evenly apart.
Buy two toothbrushes. These will rub against the record and copper
tape.
You can design the round probes your way.
Turn the crank, a twisted rubber band will make one record spin in
the opposite direction.

Try aluminum tape for air condition duct, instead of copper tape.
Try other plastic discs that are about 12" in diameter.
Try a small motor to turn the discs.

 

[Dirk Bruere]

Hello,

I'm trying to figure out a simple way in which to create a large,
static electric field (at least 10^4 V/m, if not 10^5 or even higher)
over a short distance (about, or less than, 1cm). Could I simply hook
some high voltage source up to a parallel plate type configuration and
put them close together? Obviously if the field is larger than the
dielectric strength of air this would have to be done in vacuum, but
are there any other special considerations for generating large
electric fields? Can this large field be created with "standard"
lab equipment?

First off, dry air breaks down at around 30kV/cm. Use a vacuum or
something like SF6 if you want higher field strengths. Getting the
required voltage is no problem, unless you want it very precise - use a
toy Van Der Graaf generator.

However, that is the least of your problems.
The major problem is that field strengths increase as the radius of
curvature of the conductor decreases. That's why field strength at a
needle point can be millions of volts mer metre while the applied
voltage is in the hundreds or thousands. It's why ion wind streams from
needle points.

If you have a parallel plate capacitor it's the *edges* that are very
sharp (comparatively) and where the breakdown or ion winds will start.

You need two oblate spheroids whose flat portions face each other in
order to get a uniform field over a small area.

Dirk

 

[Dirk Bruere]

----------------------------



10^5 volts/meter is not a particularly high field. For example, At 1 cm,
and normal temperature and pressure, the breakdown voltage of a 1 cm gap is
about 30KV (doesn't increase linearly with gap width). This is for a uniform
gap - either large plates with radiused edges (to eliminate edge effects),
or, as used in labs, spheres of the order of 20 to 30cm diameter.

Now, if you are going to put something into this field, the breakdown
voltage may be significantly reduced.

However, from the tenor of your question, I strongly suggest that you stay
away from high voltage experimentation until you learn more.

Which reminds me.
Do not on any account use a high current PSU! You will probably die!
Even a TV CRT HV supply at 25kV and a few mA will cause a massive shock
and possibly burns if you mess with it. The only bonus being that it
will probably not kill you, unless you are unlucky.

30kV at amperes will blast the flesh from your bones.
10mA will hurt, 100mA will kill.

Dirk

 

[[email protected]]

I'm trying to figure out a simple way in which to create a large,
static electric field (at least 10^4 V/m, if not 10^5 or even higher)
over a short distance (about, or less than, 1cm). Could I simply hook
some high voltage source up to a parallel plate type configuration and
put them close together? Obviously if the field is larger than the
dielectric strength of air this would have to be done in vacuum, but
are there any other special considerations for generating large
electric fields? Can this large field be created with "standard"
lab equipment?

Check http://www.Exair.com

 

[Dirk Bruere]

First off, dry air breaks down at around 30kV/cm. Use a vacuum or
something like SF6 if you want higher field strengths. Getting the
required voltage is no problem, unless you want it very precise - use a
toy Van Der Graaf generator.

However, that is the least of your problems.
The major problem is that field strengths increase as the radius of
curvature of the conductor decreases. That's why field strength at a
needle point can be millions of volts mer metre while the applied
voltage is in the hundreds or thousands. It's why ion wind streams from
needle points.

If you have a parallel plate capacitor it's the *edges* that are very
sharp (comparatively) and where the breakdown or ion winds will start.

You need two oblate spheroids whose flat portions face each other in
order to get a uniform field over a small area.

This site might be of interest since part of it deals with HV circuits
and discharges in a relatively safe manner
http://www.electricstuff.co.uk/

Dirk