Electrically charged sphere in a vacuum

[Kerry Soileau]

If the negative charge on a sphere in a vacuum is increased
sufficiently, do electrons begin to escape from the sphere into
vacuum? If so, is the physics similar to that of the photoelectric
effect work function concept?

Thanks for any references/insight on this question.

[[Mod. note -- I think the answers to your questions are "yes" and
"yes". More detailed discussions from the newsgroup would be welcome.
-- jt]]

[Roland Franzius]

Am 07.12.2016 um 07:41 schrieb Kerry Soileau:
> If the negative charge on a sphere in a vacuum is increased
> sufficiently, do electrons begin to escape from the sphere into
> vacuum? If so, is the physics similar to that of the photoelectric
> effect work function concept?
>
> Thanks for any references/insight on this question.
>
> [[Mod. note -- I think the answers to your questions are "yes" and
> "yes". More detailed discussions from the newsgroup would be welcome.
> -- jt]]
>

This is a nice question, its complete anwser filling a monograph.

Sloterdijk, a German philosopher and TV-host has written a trilogy of spheres.

https://www.amazon.com/Bubbles-Spheres-Microspherology-Semiotext-Foreign/dp/1584351047/ref=sr_1_2?ie=UTF8&qid=1481101571&sr=8-2&keywords=sloterdijk

1. A charged sphere is the boundary of a conducting ball.

2. Classically the charged conducting ball has its non compensated
negative charge concentrated on its 2-d surface sphere.

The D-field strength there is the charge density by definition givrn in
As/m^2. The E-field strength is E=D/esps0 = Q/(4 pi eps0 r^2) in V/m.

3. A single classical pointlike electron will leave the charged sphere
if the local radial energy difference q E.dr over the radial extension
dr of the quantum surface states is larger than the negativ binding
energy in surface states of the conduction band.

4. An educated guess for the magnitudes of ionisation energies in an
external field of solid state conduction band electrons is 1eV binding
energy and some lattice constants of radial conduction band surface
states extension. This is a rather natural assumption, because the
electric outer E-field is damped exponentially in the forbidden inner of
the ball exactly by an expoential decaying charge density (div D=rho).

5. For a mathematically ideal smooth sphere, an ionisation field
strength of 1 V/nm gives a charge of Q= 4 pi eps0 r^2 *1 V/nm

with a value
http://physics.nist.gov/cgi-bin/cuu/Value?ep0

of ~ 10^-12 As/Vm

Q = 4 pi 10^-12 As/Vm r^2 *10^9 V/m = 10^-2 As/m^2 r^2

This estimate yields a bound of 100 As on an ideal sphere of radius 1 cm
and 1 As for 1 mm.

6. A polished sphere, optically ideal reflecting, has irregularities of
- lets say - surface curvature radius less than a wave length of visible
light: 400 nm=10^-9m. The Laplace equation for the outer field demands
that the charge is concentrated in such eminent edges with a spraying
field strength of D. The ionisaton charge in a real experiment depends
on the smoothness alone.

7. The description outlined here is a first approximation to quantum
thermo-electrodynamics. It involves filling the conduction surface band
with surface one-particle free states for a fermionic plasma gas
observing the Pauli principle, temperature dependence of mixed states in
quantum statistics and vacuum-surface effect of field modes known under
the name Casimir effect.

8. The physicists in the lab trivially observe an electronic atmosphere
of free electrons of some nonzero temperature around any charged or non
charged sphere. It is desribed by the term "surface bindíng energy" and
appears as the characteristic energy step in the barometric formula fo
the exponentially decaying radial density.

The thermodynamic equilibrium principle as well as the quantum principle
of minimal kinetic energy, expressed by the minimalization of variation
of density in quantum mechanics, demands that no possibly reachable
volume element of space has a zero expectation to catch a free electron
there. See "tunnel effect" for the extension of states into
energetically forbidden areas.

9. An isolated neutral sphere emits or absorbes a certain amount of
extra charges from the environment in order to minmize its total inner
and outer electric field energy. And additionally this amount is a
volatile quantity. And the eletron field state is fluctuating too, the
deeper reason for the Casimir effect, that may be expressed by squares
of fluctuations of the quantized external electric field modes, that
whose individual shape and energy encode strongly the geometry of the
conducting boundaries.

--

Roland Franzius

[Poutnik]

Dne 07/12/2016 v 07:41 Kerry Soileau napsal(a):
> If the negative charge on a sphere in a vacuum is increased
> sufficiently, do electrons begin to escape from the sphere into
> vacuum? If so, is the physics similar to that of the photoelectric
> effect work function concept?
>
> Thanks for any references/insight on this question.
>
> [[Mod. note -- I think the answers to your questions are "yes" and
> "yes". More detailed discussions from the newsgroup would be welcome.
> -- jt]]
>
I have already posted this answer in sci.physics :

> If the negative charge on a sphere in a vacuum is increased
> sufficiently, do electrons begin to escape from the sphere into
> vacuum?

Yes, if the potential is sufficiently negative.

If so, is the physics similar to that of the photoelectric effect work
function concept?

Yes, it is.

If the given material ( and its surface atomic structure )
has the work function x electronvolts,
then the surface potential <= -x Volts provides enough energy
for the electron to leave the surface.

As in such a case,
the energy needed to leave the surface structure is equal or lower
than energy released by repulsion of the other charges.

Addition to the original post in sci.physics:
Due destructive vector addition of ES force at surface,
there is an energy barrier for electron to overcome.
( As analogy, imagine tight collection of small balls on the floor,
and the force needed to cause a random ball push up.)

So the absolute value of the needed negative potential
is for spontaneous escape much higher than the work function.

--
Poutnik ( The Pilgrim, Der Wanderer )

A wise man guards words he says,
as they say about him more,
than he says about the subject.

[szczepan bialek]

"Kerry Soileau" <***@gmail.com> napisa³ w wiadomo¶ci
news:3babb2e3-eaae-4331-905c-***@googlegroups.com...
> If the negative charge on a sphere in a vacuum is increased
> sufficiently, do electrons begin to escape from the sphere into
> vacuum? If so, is the physics similar to that of the photoelectric
> effect work function concept?
>
> Thanks for any references/insight on this question.

It is the field electron emission.
The all electron emissions are discused here:
http://www.nobelprize.org/nobel_prizes/physics/laureates/1928/richardson-lecture.pdf

"It has been suspected for a long time that electrons-could be pulled
out of metals without the co-operation of gases by sufficiently strong
electric fields. The effects seemed very erratic and difficult to
investigate. The reality of the phenomenon has, however, been firmly
established by the work of Gossling, of Millikan and Eyring, and of
Rother, during or a little prior to 1926, and by that of various
experimenters since then. These currents are carried by electrons and
they may be quite large. The magnitude is in- dependent of the
temperature of the emitting substance, but at the same time is a
continuous function of the applied electric field." S*

[Poutnik]

Dne 11/12/2016 v 11:10 szczepan bialek napsal(a):
> "Kerry Soileau" <***@gmail.com> napisaￜ w wiadomoￜci
> news:3babb2e3-eaae-4331-905c-***@googlegroups.com...
>> If the negative charge on a sphere in a vacuum is increased
>> sufficiently, do electrons begin to escape from the sphere into
>> vacuum? If so, is the physics similar to that of the photoelectric
>> effect work function concept?
>>
>> Thanks for any references/insight on this question.
>
> It is the field electron emission.
> The all electron emissions are discused here:
> http://www.nobelprize.org/nobel_prizes/physics/laureates/1928/richardson-lecture.pdf
>

But these are quite different scenarios.

In the former,
the electron is pushed out by mutual repulsion of the negative
charges of excessive electrons,
without acting of an external cause.

In the latter,
the electron is pulled out by force caused by an external field,
what is not dependent on the surface charge
but in the needed intensity.

--
Poutnik ( The Pilgrim, Der Wanderer )

A wise man guards words he says,
as they say about him more,
than he says about the subject.

[J. J. Lodder]

Kerry Soileau <***@gmail.com> wrote:

> If the negative charge on a sphere in a vacuum is increased
> sufficiently, do electrons begin to escape from the sphere into
> vacuum? If so, is the physics similar to that of the photoelectric
> effect work function concept?

An infinite vacuum doesn't exist.
There must be other conductors somewhere.
So what matters is not the charge on the sphere,
but the field strength at its surface.

Field emission will occur, in sufficiently strong fields.
(a needle tip is a practical way of concentrating the field)

But the electrons will not 'escape into the vacuum'.
They will follow a field line to somewhere else,
where there is a shortage of electrons,

Jan

[Poutnik]

Dne 11/12/2016 v 11:10 J. J. Lodder napsal(a):
> Kerry Soileau <***@gmail.com> wrote:
>
>> If the negative charge on a sphere in a vacuum is increased
>> sufficiently, do electrons begin to escape from the sphere into
>> vacuum? If so, is the physics similar to that of the photoelectric
>> effect work function concept?
>
> An infinite vacuum doesn't exist.
> There must be other conductors somewhere.

Not necesserily close enough to play any significant role.

> So what matters is not the charge on the sphere,
> but the field strength at its surface.

But as both quantity are directly related,
charge does matter.
>
> But the electrons will not 'escape into the vacuum'.
> They will follow a field line to somewhere else,
> where there is a shortage of electrons,
>

Electrons can escape anywhere where is higher potential,
therefore lower eventual potential energy.

--
Poutnik ( The Pilgrim, Der Wanderer )

A wise man guards words he says,
as they say about him more,
than he says about the subject.

[J. J. Lodder]

Poutnik <***@gmail.com> wrote:

> Dne 11/12/2016 v 11:10 J. J. Lodder napsal(a):
> > Kerry Soileau <***@gmail.com> wrote:
> >
> >> If the negative charge on a sphere in a vacuum is increased
> >> sufficiently, do electrons begin to escape from the sphere into
> >> vacuum? If so, is the physics similar to that of the photoelectric
> >> effect work function concept?
> >
> > An infinite vacuum doesn't exist.
> > There must be other conductors somewhere.
>
> Not necesserily close enough to play any significant role.

They play a significant role even when placed at infinity.
For example, place the negatively charged sphere
inside a bigger concentric sphere that is charged even more negatively,
and take the limit of the outer sphere going to infinity.

In other words, even if you idealise to nothing else present
you still must specify the potential at infinity.
Just 'in vacuum' is not enough.

> > So what matters is not the charge on the sphere,
> > but the field strength at its surface.
>
> But as both quantity are directly related,
> charge does matter.

See above,

Jan

[Poutnik]

Dne 13/12/2016 v 08:10 J. J. Lodder napsal(a):
> Poutnik <***@gmail.com> wrote:
>
>> Dne 11/12/2016 v 11:10 J. J. Lodder napsal(a):
>>> Kerry Soileau <***@gmail.com> wrote:
>>>
>>>> If the negative charge on a sphere in a vacuum is increased
>>>> sufficiently, do electrons begin to escape from the sphere into
>>>> vacuum? If so, is the physics similar to that of the photoelectric
>>>> effect work function concept?
>>>
>>> An infinite vacuum doesn't exist.
>>> There must be other conductors somewhere.
>>
>> Not necesserily close enough to play any significant role.
>
> They play a significant role even when placed at infinity.
> For example, place the negatively charged sphere
> inside a bigger concentric sphere that is charged even more negatively,
> and take the limit of the outer sphere going to infinity.
>
> In other words, even if you idealise to nothing else present
> you still must specify the potential at infinity.
> Just 'in vacuum' is not enough.

Potential in infinity is zero by definition. :-)

--
Poutnik ( The Pilgrim, Der Wanderer )

A wise man guards words he says,
as they say about him more,
than he says about the subject.

[[Mod. note -- Actually the potential at infinity is arbitrary -- we
can choose it to be any (direction-independent) value we want without
changing any observable physics. Choosing this value to be zero is a
common convention, not a definition.
-- jt]]

[Lauretta Nagle]

Poutnik wrote:

>> In other words, even if you idealise to nothing else present you still
>> must specify the potential at infinity.
>> Just 'in vacuum' is not enough.
>
> Potential in infinity is zero by definition.

What definition would be that, yours?

[J. J. Lodder]

Poutnik <***@gmail.com> wrote:

> Dne 13/12/2016 v 08:10 J. J. Lodder napsal(a):
> > Poutnik <***@gmail.com> wrote:
> >
> >> Dne 11/12/2016 v 11:10 J. J. Lodder napsal(a):
> >>> Kerry Soileau <***@gmail.com> wrote:
> >>>
> >>>> If the negative charge on a sphere in a vacuum is increased
> >>>> sufficiently, do electrons begin to escape from the sphere into
> >>>> vacuum? If so, is the physics similar to that of the photoelectric
> >>>> effect work function concept?
> >>>
> >>> An infinite vacuum doesn't exist.
> >>> There must be other conductors somewhere.
> >>
> >> Not necesserily close enough to play any significant role.
> >
> > They play a significant role even when placed at infinity.
> > For example, place the negatively charged sphere
> > inside a bigger concentric sphere that is charged even more negatively,
> > and take the limit of the outer sphere going to infinity.
> >
> > In other words, even if you idealise to nothing else present
> > you still must specify the potential at infinity.
> > Just 'in vacuum' is not enough.
>
> Potential in infinity is zero by definition. :-)

Excercise: consider a charged half-space.
Calculate the potential at infinity.

Equivalently: given an infinite flat earth.
Calculate the potential at infinity above it.

More genrerally: absolute potential has no physical meaning,
only potential differences have,
so the potential at infinity can be chosen arbitrarily,

Jan

[Poutnik]

Dne 18/12/2016 v 09:52 J. J. Lodder napsal(a):
> Poutnik <***@gmail.com> wrote:
>
>>
>> Potential in infinity is zero by definition. :-)
>
> Excercise: consider a charged half-space.
> Calculate the potential at infinity.
>
> Equivalently: given an infinite flat earth.
> Calculate the potential at infinity above it.
>
> More genrerally: absolute potential has no physical meaning,
> only potential differences have,
> so the potential at infinity can be chosen arbitrarily,
>
Exactly taken, I agree.

What I meant were physically real scenarios.
Infinite objects do not fit there, so gedankens
based on them can easily trick me out, I admit.

By infinity I have meant a physical infinity
in the sense being far enough from disturbances
to keep them physically negligible.

And the potential value at this place
can be considered as a pseudoabsolute zero.

--
Poutnik ( The Pilgrim, Der Wanderer )

A wise man guards words he says,
as they say about him more,
than he says about the subject.

[Jos Bergervoet]

On 12/18/2016 9:52 AM, J. J. Lodder wrote:
> Poutnik <***@gmail.com> wrote:
>> Dne 13/12/2016 v 08:10 J. J. Lodder napsal(a):
>>> Poutnik <***@gmail.com> wrote:
>>>> Dne 11/12/2016 v 11:10 J. J. Lodder napsal(a):
>>>>> Kerry Soileau <***@gmail.com> wrote:
>>>>>
>>>>>> If the negative charge on a sphere in a vacuum is increased
>>>>>> sufficiently, do electrons begin to escape from the sphere into
>>>>>> vacuum? If so, is the physics similar to that of the photoelectric
>>>>>> effect work function concept?
>>>>>
>>>>> An infinite vacuum doesn't exist.
>>>>> There must be other conductors somewhere.
>>>>
>>>> Not necesserily close enough to play any significant role.
>>>
>>> They play a significant role even when placed at infinity.
>>> For example, place the negatively charged sphere
>>> inside a bigger concentric sphere that is charged even more negatively,
>>> and take the limit of the outer sphere going to infinity.
>>>
>>> In other words, even if you idealise to nothing else present
>>> you still must specify the potential at infinity.
>>> Just 'in vacuum' is not enough.
>>
>> Potential in infinity is zero by definition. :-)
>
> Excercise: consider a charged half-space.
> Calculate the potential at infinity.
>
> Equivalently: given an infinite flat earth.
> Calculate the potential at infinity above it.
>
> More genrerally: absolute potential has no physical meaning,
> only potential differences have,

No Jan, they haven't. As you know very well!

The scalar potential is not physical, only the fields are. You
can change the potential freely by any gauge transformation and
still describe the same *physical* situation.

--
Jos

[Roland Franzius]

Am 18.12.2016 um 22:36 schrieb Jos Bergervoet:

> The scalar potential is not physical, only the fields are. You
> can change the potential freely by any gauge transformation and
> still describe the same *physical* situation.
>


Yes, in an empty infinite euclidean space.

There, the kernel of the Poisson equation, the linear space with Laplace
f=0, is the space of linear functions, not only the constant functions.
Linear potentials would mean constant electric fields with div E=0. This
is exluded as a solution with inifite field energy
int E^2 d^3x = oo in open infinite R^3. But classical point charge
fields are excluded by the same argument, unfortunately.

Now, with the knowlege that the electromagnetic potentials are gauge
fields introduced to fix the momentum 4-vector point of reference for a
swarm of charged elementary particles by the canonical substitution

(E/c =p^2/(2mc), p ) -> (E/c - q A0(x), p - q A(x)),

try to answer the same question at least for three particles (hint: its
trivial only for up to two particles).

Next step: Try to answer the gauge freedom class of potentials in the
compact empty space S^3, the uniform 3-sphere without a boundary. Does
there exist a single point charge solution with div E = everywhere?

--

Roland Franzius

[szczepan bialek]

"J. J. Lodder" <***@de-ster.demon.nl> napisa³ w wiadomo¶ci
news:1mxw58i.vpayd01q09v41N%***@de-ster.demon.nl...
> Kerry Soileau <***@gmail.com> wrote:
>
>
> Field emission will occur, in sufficiently strong fields.
> (a needle tip is a practical way of concentrating the field)
>
> But the electrons will not 'escape into the vacuum'.
> They will follow a field line to somewhere else,
> where there is a shortage of electrons,

In the interplanetary space is the solar wind (protons and electrons).
So the electrons are pushed out into such medium.
S*

[Poutnik]

On 12/11/2016 11:52 PM, szczepan bialek wrote:
> "J. J. Lodder" <***@de-ster.demon.nl> napisa=B3 w wiadomo=B6ci
> news:1mxw58i.vpayd01q09v41N%***@de-ster.demon.nl...
>> Kerry Soileau <***@gmail.com> wrote:
>>
>>
>> Field emission will occur, in sufficiently strong fields.
>> (a needle tip is a practical way of concentrating the field)
>>
>> But the electrons will not 'escape into the vacuum'.
>> They will follow a field line to somewhere else,
>> where there is a shortage of electrons,
>
> In the interplanetary space is the solar wind (protons and electrons).
> So the electrons are pushed out into such medium.
> S*
>

I rather would not call it a medium.

concerning an electron emitted from a solid phase,
interactions with remote particles in high degree vacuum
about 11 atoms per cm3 *) is negligible
wrt interaction with the solid phase.

These remote particles play no role in ability
to be transferred to or stay in vacuum.


*) https://en.wikipedia.org/wiki/Vacuum#Examples

--=20
Poutnik ( The Pilgrim, Der Wanderer )

A wise man guards words he says,
as they say about him more,
than he says about the subject.

[J. J. Lodder]

szczepan bialek <***@wp.pl> wrote:

> "J. J. Lodder" <***@de-ster.demon.nl> napisa" w wiadomo=B6ci=20
> news:1mxw58i.vpayd01q09v41N%***@de-ster.demon.nl...
> > Kerry Soileau <***@gmail.com> wrote:
> >
> >
> > Field emission will occur, in sufficiently strong fields.
> > (a needle tip is a practical way of concentrating the field)
> >
> > But the electrons will not 'escape into the vacuum'.
> > They will follow a field line to somewhere else,
> > where there is a shortage of electrons,
>=20
> In the interplanetary space is the solar wind (protons and electrons).
> So the electrons are pushed out into such medium.
> S*

Such a medium is a medium, and not a vacuum.
(a plasma, to be precise)

An isolated conductor placed in a plasma
will rapidly acquire a potential
such that the net current to or from it is zero.

Jan

[Roland Franzius]

Am 13.12.2016 um 08:10 schrieb J. J. Lodder:
> szczepan bialek <***@wp.pl> wrote:
>
>> "J. J. Lodder" <***@de-ster.demon.nl> napisa" w wiadomo¶ci
>> news:1mxw58i.vpayd01q09v41N%***@de-ster.demon.nl...
>>> Kerry Soileau <***@gmail.com> wrote:
>>>
>>>
>>> Field emission will occur, in sufficiently strong fields.
>>> (a needle tip is a practical way of concentrating the field)
>>>
>>> But the electrons will not 'escape into the vacuum'.
>>> They will follow a field line to somewhere else,
>>> where there is a shortage of electrons,
>>
>> In the interplanetary space is the solar wind (protons and electrons).
>> So the electrons are pushed out into such medium.
>> S*
>
> Such a medium is a medium, and not a vacuum.
> (a plasma, to be precise)
>
> An isolated conductor placed in a plasma
> will rapidly acquire a potential
> such that the net current to or from it is zero.

That the expectation. As always there is a dynamics of fluctuations in a
temperature state.

All modes of charg and current distributions are degrees of freedom in a
thermodynamical system at equilibrium at certain temperature. They can
be modelled as small oszillations around the equilibrium state.

With the standard mode energy distributions of ocillations given, these
modes will be activated according to the Boltzmann distribution e^-(E/kT).

This is the point where all considerations of the conducting sphere in
courses of electrodynamics stop. Mostly because its a fuzzy open
frontier of reliable knowlegde.

--

Roland Franzius

[szczepan bialek]

"J. J. Lodder" <***@de-ster.demon.nl> napisa³ w wiadomo¶ci
news:1my61vv.1lcve9017fjpcuN%***@de-ster.demon.nl...
> szczepan bialek <***@wp.pl> wrote:
>
>> "J. J. Lodder" <***@de-ster.demon.nl> napisa" w wiadomo=B6ci=20
>> news:1mxw58i.vpayd01q09v41N%***@de-ster.demon.nl...
>> > Kerry Soileau <***@gmail.com> wrote:
>> >
>> >
>> > Field emission will occur, in sufficiently strong fields.
>> > (a needle tip is a practical way of concentrating the field)
>> >
>> > But the electrons will not 'escape into the vacuum'.
>> > They will follow a field line to somewhere else,
>> > where there is a shortage of electrons,
>>=20
>> In the interplanetary space is the solar wind (protons and electrons).
>> So the electrons are pushed out into such medium.
>> S*
>
> Such a medium is a medium, and not a vacuum.
> (a plasma, to be precise)

Rare plasma.
>
> An isolated conductor placed in a plasma
> will rapidly acquire a potential
> such that the net current to or from it is zero.

To be precise the conductor with deficyt or excess of electrons gain or lost
them.
The speed is the surface structure dependent.
S*

[Rich L.]

On Wednesday, December 7, 2016 at 12:41:38 AM UTC-6, Kerry Soileau wrote:
> If the negative charge on a sphere in a vacuum is increased
> sufficiently, do electrons begin to escape from the sphere into
> vacuum? If so, is the physics similar to that of the photoelectric
> effect work function concept?
>
> Thanks for any references/insight on this question.
>
> [[Mod. note -- I think the answers to your questions are "yes" and
> "yes". More detailed discussions from the newsgroup would be welcome.
> -- jt]]

What you are describing is field emission. Some electron microscopes
use this as the electron source from a specially prepared very fine
needle with a very sharp (small radius) tip. Rolands answer discusses
some details of this process. For these fine tips used in electron
microscopes the atoms of the metal do represent significant deviations
from a perfect sphere.

Rich L.

[John Heath]

On Wednesday, December 7, 2016 at 1:57:40 PM UTC-5, Poutnik wrote:
> Dne 07/12/2016 v 07:41 Kerry Soileau napsal(a):
> > If the negative charge on a sphere in a vacuum is increased
> > sufficiently, do electrons begin to escape from the sphere into
> > vacuum? If so, is the physics similar to that of the photoelectric
> > effect work function concept?
> >
> > Thanks for any references/insight on this question.
> >
> > [[Mod. note -- I think the answers to your questions are "yes" and
> > "yes". More detailed discussions from the newsgroup would be welcome.
> > -- jt]]
> >
> I have already posted this answer in sci.physics :
>
> > If the negative charge on a sphere in a vacuum is increased
> > sufficiently, do electrons begin to escape from the sphere into
> > vacuum?
>
> Yes, if the potential is sufficiently negative.
>
> If so, is the physics similar to that of the photoelectric effect work
> function concept?
>
> Yes, it is.
>
> If the given material ( and its surface atomic structure )
> has the work function x electronvolts,
> then the surface potential <= -x Volts provides enough energy
> for the electron to leave the surface.
>
> As in such a case,
> the energy needed to leave the surface structure is equal or lower
> than energy released by repulsion of the other charges.
>
> Addition to the original post in sci.physics:
> Due destructive vector addition of ES force at surface,
> there is an energy barrier for electron to overcome.
> ( As analogy, imagine tight collection of small balls on the floor,
> and the force needed to cause a random ball push up.)
>
> So the absolute value of the needed negative potential
> is for spontaneous escape much higher than the work function.
>
> --
> Poutnik ( The Pilgrim, Der Wanderer )
>
> A wise man guards words he says,
> as they say about him more,
> than he says about the subject.

If it is a cube not a sphere then electrons will leave at a lower
voltage potential at the sharp corners of the cube compared to the flat
surfaces. The temperature of the cube changes the voltage potentials
that will cause an electron to leave. The point I wanted to make is it
is not as easy as the ionization voltage of the atom.

[Poutnik]

Dne 11/12/2016 v 11:11 John Heath napsal(a):
>
> If it is a cube not a sphere then electrons will leave at a lower
> voltage potential at the sharp corners of the cube compared to the flat
> surfaces. The temperature of the cube changes the voltage potentials
> that will cause an electron to leave. The point I wanted to make is it
> is not as easy as the ionization voltage of the atom.
>

As I have said before, the work function depends
on both material AND the surface structure.

The macro shape belongs to the surface structure.

It should be as well obvious
the needed energy = work function - kinetic energy.
The mean kinetic energy is proportional to temperature.

Neither I have said it is as easy
as the ionization voltage of the atom.

--
Poutnik ( The Pilgrim, Der Wanderer )

A wise man guards words he says,
as they say about him more,
than he says about the subject.

[charly]

Kerry Soileau wrote:
> If the negative charge on a sphere in a vacuum is increased
> sufficiently, do electrons begin to escape from the sphere into
> vacuum? If so, is the physics similar to that of the photoelectric
> effect work function concept?
>
> Thanks for any references/insight on this question.
>
> [[Mod. note -- I think the answers to your questions are "yes" and
> "yes". More detailed discussions from the newsgroup would be welcome.
> -- jt]]

Question : would this problem not be rather similar to a glass, filled
with water, inverted and under gravity? The water falls out, unless its
surface is stabilized by for example a sheet of paper.

Quantum tunneling of electrons leeds to a formula (Fowler Nordheim). But
its results are reached only for sharp points. For flat surfaces there
is a disagreement with experiment : the field reached is lower by a
factor 10-20, even for well polished surfaces. Stability problem?

charles

[John Heath]

On Tuesday, February 13, 2018 at 11:36:33 AM UTC-5, charly wrote:
> Kerry Soileau wrote:
> > If the negative charge on a sphere in a vacuum is increased
> > sufficiently, do electrons begin to escape from the sphere into
> > vacuum? If so, is the physics similar to that of the photoelectric
> > effect work function concept?
> >
> > Thanks for any references/insight on this question.
> >
> > [[Mod. note -- I think the answers to your questions are "yes" and
> > "yes". More detailed discussions from the newsgroup would be welcome.
> > -- jt]]
>
> Question : would this problem not be rather similar to a glass, filled
> with water, inverted and under gravity? The water falls out, unless its
> surface is stabilized by for example a sheet of paper.
>
> Quantum tunneling of electrons leeds to a formula (Fowler Nordheim). But
> its results are reached only for sharp points. For flat surfaces there
> is a disagreement with experiment : the field reached is lower by a
> factor 10-20, even for well polished surfaces. Stability problem?
>
> charles

I little bit that could be helpful. Hard to say until it is on the table
to be seen. I was talking to someone that was doing model rendering of
a coulomb force in a vacuum in 3 dimensions. The point of interest was
sphere vs cube with sharp edges. To my surprise a Coulomb force from a
cube in a vacuum becomes a sphere surprisingly fast. Within 1 diameter
of the cube the coulomb force is almost a sphere. At 2 diameters you can
not tell from the human eye that the Coulomb force started from a cube.
It is perfectly round in force. I would venture a guess that it is the
spreading out in all 3 dimensions that causes it to average out quicker
than one would intuitively think. Well it is now on the table. Is this
helpful?

[Jos Bergervoet]

On 2/13/2018 5:36 PM, charly wrote:
> Kerry Soileau wrote:
>> If the negative charge on a sphere in a vacuum is increased
>> sufficiently, do electrons begin to escape from the sphere into
>> vacuum? If so, is the physics similar to that of the photoelectric
>> effect work function concept?
>>
>> Thanks for any references/insight on this question.
>>
>> [[Mod. note -- I think the answers to your questions are "yes" and
>> "yes". More detailed discussions from the newsgroup would be welcome.
>> -- jt]]
>
> Question : would this problem not be rather similar to a glass, filled
> with water, inverted and under gravity? The water falls out, unless its
> surface is stabilized by for example a sheet of paper.
>
> Quantum tunneling of electrons leeds to a formula (Fowler Nordheim). But
> its results are reached only for sharp points. For flat surfaces there
> is a disagreement with experiment : the field reached is lower by a
> factor 10-20, even for well polished surfaces. Stability problem?

Or maybe polished surfaces are not flat? Even if you have a
perfectly stacked crystal, just one single atom adsorbed on
its surface would create big field gradients and may already
give you the order of magnitude difference you mention.

--
Jos

[charly]

Jos Bergervoet wrote:
> On 2/13/2018 5:36 PM, charly wrote:
>> Kerry Soileau wrote:
>>> If the negative charge on a sphere in a vacuum is increased
>>> sufficiently, do electrons begin to escape from the sphere into
>>> vacuum? If so, is the physics similar to that of the photoelectric
>>> effect work function concept?
>>>
>>> Thanks for any references/insight on this question.
>>>
>>> [[Mod. note -- I think the answers to your questions are "yes" and
>>> "yes". More detailed discussions from the newsgroup would be welcome.
>>> -- jt]]
>>
>> Question : would this problem not be rather similar to a glass, filled
>> with water, inverted and under gravity? The water falls out, unless its
>> surface is stabilized by for example a sheet of paper.
>>
>> Quantum tunneling of electrons leeds to a formula (Fowler Nordheim). But
>> its results are reached only for sharp points. For flat surfaces there
>> is a disagreement with experiment : the field reached is lower by a
>> factor 10-20, even for well polished surfaces. Stability problem?
>
> Or maybe polished surfaces are not flat? Even if you have a
> perfectly stacked crystal, just one single atom adsorbed on
> its surface would create big field gradients and may already
> give you the order of magnitude difference you mention.
>

A single adsorbed atom would indeed create field gradients. But I
suppose that even on a perfectly stacked crystal, the field at the
surface is also not free from big gradients. An adsorbed atom would
probably just increase matters. As a model one could take the field
enhancement at the top of a semisphere on a flat plane : about a factor
3 (as I read in paper from the internet on vacuum breakdown some time
(years) ago). But of course, on top of this semisphere one could place
another semisphere an order of magnitude smaller, so that the top of the
larger one could be considered flat.: yet another factor 3 ... and so
on, every order of magnitude would result in a factor 3 increase in
field strength.

However increasing electrical potential eventually leads to a
flash-over, a catastrophic breakdown. That is why I was thinking of
stability questions as I mentionned at first. And most interesting is of
course : what is the max field that can practically be reached : 4e9 V/m
(~=Fowler Nordheim), or 1e9 V/m, 4e8 V/m , 2e8 V/m ???

A similar problem is the max field strength in a dielectricum, for
example with an error, a sphere inside where the dielectricum is missing
... I read on wikipedia that the max field in diamond for example is 2e9
V/m. Or in a flash memory device 8e8 V/m is used to program the memory
... So apparently the field in a dielectricum might be larger than at
the surface of a metal in a vacuum?

Charles

[charly]

Kerry Soileau wrote:
> If the negative charge on a sphere in a vacuum is increased
> sufficiently, do electrons begin to escape from the sphere into
> vacuum? If so, is the physics similar to that of the photoelectric
> effect work function concept?
>
> Thanks for any references/insight on this question.
>
> [[Mod. note -- I think the answers to your questions are "yes" and
> "yes". More detailed discussions from the newsgroup would be welcome.
> -- jt]]
>

Question : would this problem not be rather similar to a glass filled with
water, inverted, and under gravity? The water falls out, unless its surface
is stabilized by for example a sheet of paper.

Quantum tunneling of electrons leeds to a formula (Fowler Nordheim), but in
experiment its results only agree for sharp points. For flat surfaces there
is a disagreement by some factor (at least 10-20) which is attributed to
surface irregularities. But maybe stability issues play a major role?

charles

[Gerry Quinn]

In article <p5uj8v$dur$***@dont-email.me>, ***@skynet.be says...
>
> Kerry Soileau wrote:
> > If the negative charge on a sphere in a vacuum is increased
> > sufficiently, do electrons begin to escape from the sphere into
> > vacuum? If so, is the physics similar to that of the photoelectric
> > effect work function concept?
> >
> > Thanks for any references/insight on this question.
> >
> > [[Mod. note -- I think the answers to your questions are "yes" and
> > "yes". More detailed discussions from the newsgroup would be welcome.
> > -- jt]]
> >
>
> Question : would this problem not be rather similar to a glass filled with
> water, inverted, and under gravity? The water falls out, unless its surface
> is stabilized by for example a sheet of paper.
>
> Quantum tunneling of electrons leeds to a formula (Fowler Nordheim), but in
> experiment its results only agree for sharp points. For flat surfaces there
> is a disagreement by some factor (at least 10-20) which is attributed to
> surface irregularities. But maybe stability issues play a major role?

Of course all these discussions presuppose that there are electrons
already hanging around in the sphere.

I assume if it is a negatively charged sphere of anti-matter, or some
other substance that contains no electrons, electron emissions would not
begin until the charge is sufficient that electron-positron pair
production is energetically favoured. [Hmmm - are science fictional
super-capacitors as used in death stars etc. partly composed of anti-
matter?]

For a sphere containing real electrons, there are probably many
processes and effects that can materially aid their escape, so the
emissions will start earlier than theory predicts.

- Gerry Quinn

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

[Lawrence Crowell]

On Wednesday, December 7, 2016 at 12:41:38 AM UTC-6, Kerry Soileau wrote:
> If the negative charge on a sphere in a vacuum is increased
> sufficiently, do electrons begin to escape from the sphere into
> vacuum? If so, is the physics similar to that of the photoelectric
> effect work function concept?
>
> Thanks for any references/insight on this question.
>
> [[Mod. note -- I think the answers to your questions are "yes" and
> "yes". More detailed discussions from the newsgroup would be welcome.
> -- jt]]

It is related to the photoelectric effect if there is an increase in the
flux of electrons leaving the sphere with an increase in photon
irradiance incident on the sphere.

LC

[John Heath]

On Saturday, February 17, 2018 at 5:14:35 AM UTC-5, Lawrence Crowell wrote:
> On Wednesday, December 7, 2016 at 12:41:38 AM UTC-6, Kerry Soileau wrote:
> > If the negative charge on a sphere in a vacuum is increased
> > sufficiently, do electrons begin to escape from the sphere into
> > vacuum? If so, is the physics similar to that of the photoelectric
> > effect work function concept?
> >
> > Thanks for any references/insight on this question.
> >
> > [[Mod. note -- I think the answers to your questions are "yes" and
> > "yes". More detailed discussions from the newsgroup would be welcome.
> > -- jt]]
>
> It is related to the photoelectric effect if there is an increase in the
> flux of electrons leaving the sphere with an increase in photon
> irradiance incident on the sphere.
>
> LC

I was experimenting with micro gravity waves induced by extreme vacuum stress
caused by a rapid change in temperature of a plasma state. Some would call
that a spark plug but it sounds better the way I put it. It did not work.
However the plasma voltage breakdown in air , less air and down to a vacuum
has some surprises. Breakdown voltage goes down as air pressure goes down
until around 1 torr cm at which point the voltage breakdown of all gases
quickly points up towards infinity?

https://en.wikipedia.org/wiki/Paschen%27s_law

Infinity is a big word. Would it run into pair production in the 1 M volt range?
It would be elegant if it did. 1 M volt of raw energy translated into
a water fountain of electrons and positrons. No reason for heat as it would
be energy going directly to matter. A nice way to demonstrate the weight
of E=MC^2.

The strangest part has to do with distance of a voltage break down gap.
I will quote.

With a constant pressure, the voltage needed to cause an arc reduced as
the gap size was reduced but only to a point. As the gap was reduced
further, the voltage required to cause an arc began to rise and again
exceeded its original value.

End quote.

This is more plasma physics but it is related to an electron leaving the
surface of a sphere in a vacuum. Charged particles in a vacuum are free
do move without resistance as can be seen with charged particles coming
from our sun. This returns the focus to the Coulomb force holding the
electron to a sphere. let us make the sphere copper to eliminate Mr
proton from holding back the electron from leaving a sphere. This would
mean that the voltage to remove 1 electron from a copper sphere into a
vacuum would in the u volt range. This is not the case. What went wrong?

Note to moderators. The following may be deleted if too speculative.

There is one way out but it is speculation. Declare all leptons ,
electron muon tauon , on the standard model as products of the vacuum
not matter. Matter would only be quarks leading to protons pions ... If
this were the case then the voltage required to pull an electron off a
copper sphere that is cold and in a vacuum would be in the 1 G volt
range.

[jacobnavia]

Le 10/03/2021 11:09, Phillip Helbig (undress to reply) a écrit :

> How well do we know the value of G?
>
> G is the constant (well, as far as we know) of nature whose value is
> known with the least precision. How well do we know it? Presumably
> only Cavendish-type experiments can measure it directly. Other
> measurements of G, particularly astronomical ones, probably actually
> measure GM, or GMm. In some cases, those quantities might be known to
> more precision than G itself.
>
> Suppose G were to vary with time, or place, or (thinking of something
> like MOND here) with the acceleration in question. Could that be
> detected, or would it be masked by wrong assumptions about the mass(es)
> involved?
>
> Just as an example, would a smaller value of G and correspondingly
> higher masses be compatible with LIGO observations?

There is a very interesting article in scientific american about this:

see

https://www.scientificamerican.com/article/physicists-measure-the-gravitational-force-between-the-smallest-masses-yet/

[Moderator's note: See also https://www.aspelmeyer.quantum.at/news/ -P.H.]