# mutual capacitance?

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RichD
Guest

Tue Feb 12, 2019 12:45 am

Looking at network theory and the duality theorems,
why is there no mutual capacitance? i.e. electric
flux linkages, symmetric to mutual inductance and B flux.

--
Rich

Jasen Betts
Guest

Tue Feb 12, 2019 3:45 am

On 2019-02-11, RichD <r_delaney2001_at_yahoo.com> wrote:
Quote:
Looking at network theory and the duality theorems,
why is there no mutual capacitance? i.e. electric
flux linkages, symmetric to mutual inductance and B flux.

you'll see something like mutual capacitance in piezo-electric transformers.

--
When I tried casting out nines I made a hash of it.

Phil Hobbs
Guest

Tue Feb 12, 2019 4:45 pm

On 2/11/19 5:58 PM, RichD wrote:
Quote:
Looking at network theory and the duality theorems,
why is there no mutual capacitance? i.e. electric
flux linkages, symmetric to mutual inductance and B flux.

--
Rich

There is. It's usually just called 'capacitance', unless you need to
distinguish it from self-capacitance.

A 1-cm radius isolated sphere has a self-capacitance of 1 cm (Gaussian
units), which is about 1.12 pF.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

John Larkin
Guest

Tue Feb 12, 2019 6:45 pm

On Tue, 12 Feb 2019 10:33:31 -0500, Phil Hobbs
<pcdhSpamMeSenseless_at_electrooptical.net> wrote:

Quote:
On 2/11/19 5:58 PM, RichD wrote:
Looking at network theory and the duality theorems,
why is there no mutual capacitance? i.e. electric
flux linkages, symmetric to mutual inductance and B flux.

--
Rich

There is. It's usually just called 'capacitance', unless you need to
distinguish it from self-capacitance.

A 1-cm radius isolated sphere has a self-capacitance of 1 cm (Gaussian
units), which is about 1.12 pF.

Cheers

Phil Hobbs

There are two commonly given values for the capacitance between the
earth and the moon, 160uF and 3 uF. I think one is 2-wire capacitance
and the smaller one is 3-wire.

Where is the universe's ground lug?

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Phil Hobbs
Guest

Tue Feb 12, 2019 6:45 pm

On 2/12/19 11:47 AM, John Larkin wrote:
Quote:
On Tue, 12 Feb 2019 10:33:31 -0500, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:

On 2/11/19 5:58 PM, RichD wrote:
Looking at network theory and the duality theorems,
why is there no mutual capacitance? i.e. electric
flux linkages, symmetric to mutual inductance and B flux.

--
Rich

There is. It's usually just called 'capacitance', unless you need to
distinguish it from self-capacitance.

A 1-cm radius isolated sphere has a self-capacitance of 1 cm (Gaussian
units), which is about 1.12 pF.

Cheers

Phil Hobbs

There are two commonly given values for the capacitance between the
earth and the moon, 160uF and 3 uF. I think one is 2-wire capacitance
and the smaller one is 3-wire.

Where is the universe's ground lug?

Well, there's some silly speculation about that we're living in a
simulation, in which case it would be Node 0. ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

John Larkin
Guest

Tue Feb 12, 2019 10:45 pm

On Tue, 12 Feb 2019 11:58:57 -0500, Phil Hobbs
<pcdhSpamMeSenseless_at_electrooptical.net> wrote:

Quote:
On 2/12/19 11:47 AM, John Larkin wrote:
On Tue, 12 Feb 2019 10:33:31 -0500, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:

On 2/11/19 5:58 PM, RichD wrote:
Looking at network theory and the duality theorems,
why is there no mutual capacitance? i.e. electric
flux linkages, symmetric to mutual inductance and B flux.

--
Rich

There is. It's usually just called 'capacitance', unless you need to
distinguish it from self-capacitance.

A 1-cm radius isolated sphere has a self-capacitance of 1 cm (Gaussian
units), which is about 1.12 pF.

Cheers

Phil Hobbs

There are two commonly given values for the capacitance between the
earth and the moon, 160uF and 3 uF. I think one is 2-wire capacitance
and the smaller one is 3-wire.

Where is the universe's ground lug?

Well, there's some silly speculation about that we're living in a
simulation, in which case it would be Node 0. ;)

Cheers

Phil Hobbs

We could connect to the celestial sphere, the one with all the track
lights.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

Phil Hobbs
Guest

Wed Feb 13, 2019 12:45 am

On 2/12/19 6:17 PM, RichD wrote:
Quote:
On February 12, Phil Hobbs wrote:
Looking at network theory and the duality theorems,
why is there no mutual capacitance? i.e. electric
flux linkages, symmetric to mutual inductance and B flux.

There is. It's usually just called 'capacitance', unless you need to
distinguish it from self-capacitance.

I picture the analog of two isolated coils, magnetically
linked: two isolated capacitors, the flux of the 'primary'
transmits through the 'secondary'. Why no such device?

A 1-cm radius isolated sphere has a self-capacitance of 1 cm (Gaussian
units), which is about 1.12 pF.

Well, I have in mind your basic two plate capacitor.
I don't recall self-capacitance -

--
Rich

What you're describing is precisely the mutual capacitance. It's the
change of the charge on plate 1 due to the change in voltage on plate 2.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

RichD
Guest

Wed Feb 13, 2019 12:45 am

On February 12, Phil Hobbs wrote:
Quote:
Looking at network theory and the duality theorems,
why is there no mutual capacitance? i.e. electric
flux linkages, symmetric to mutual inductance and B flux.

There is. It's usually just called 'capacitance', unless you need to
distinguish it from self-capacitance.

I picture the analog of two isolated coils, magnetically
linked: two isolated capacitors, the flux of the 'primary'
transmits through the 'secondary'. Why no such device?

Quote:
A 1-cm radius isolated sphere has a self-capacitance of 1 cm (Gaussian
units), which is about 1.12 pF.

Well, I have in mind your basic two plate capacitor.
I don't recall self-capacitance -

--
Rich

RichD
Guest

Wed Feb 13, 2019 12:45 am

On February 12, John Larkin wrote:
Quote:
Looking at network theory and the duality theorems,
why is there no mutual capacitance? i.e. electric
flux linkages, symmetric to mutual inductance and B flux.

There are two commonly given values for the capacitance between the
earth and the moon, 160uF and 3 uF. I think one is 2-wire capacitance
and the smaller one is 3-wire.

2-wire, 3-wire?

--
Rich

whit3rd
Guest

Wed Feb 13, 2019 2:45 am

On Tuesday, February 12, 2019 at 3:17:53 PM UTC-8, RichD wrote:
Quote:
On February 12, Phil Hobbs wrote:

A 1-cm radius isolated sphere has a self-capacitance of 1 cm (Gaussian
units), which is about 1.12 pF.

Well, I have in mind your basic two plate capacitor.
I don't recall self-capacitance -

Self-capacitance is the capacitance of an object with respect to ground, when it is
in a large grounded box. An infinite box, ideally.

Phil Hobbs
Guest

Wed Feb 13, 2019 3:45 am

On 2/12/19 8:14 PM, whit3rd wrote:
Quote:
On Tuesday, February 12, 2019 at 3:17:53 PM UTC-8, RichD wrote:
On February 12, Phil Hobbs wrote:

A 1-cm radius isolated sphere has a self-capacitance of 1 cm (Gaussian
units), which is about 1.12 pF.

Well, I have in mind your basic two plate capacitor.
I don't recall self-capacitance -

Self-capacitance is the capacitance of an object with respect to ground, when it is
in a large grounded box. An infinite box, ideally.

Ground isn't necessary. An isolated conductor with a certain amount Q
of free charge on it will have an E field. The voltage V is minus the
line integral of E dot ds from the surface to infinity. The
self-capacitance is Q/V.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

George Herold
Guest

Wed Feb 13, 2019 3:45 am

On Tuesday, February 12, 2019 at 10:33:40 AM UTC-5, Phil Hobbs wrote:
Quote:
On 2/11/19 5:58 PM, RichD wrote:
Looking at network theory and the duality theorems,
why is there no mutual capacitance? i.e. electric
flux linkages, symmetric to mutual inductance and B flux.

--
Rich

There is. It's usually just called 'capacitance', unless you need to
distinguish it from self-capacitance.

A 1-cm radius isolated sphere has a self-capacitance of 1 cm (Gaussian
units), which is about 1.12 pF.

Huh right, I had this picture of three hunks of stuff with various
inter-capacitances. But that starts with one hunk!

George H.

Quote:

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

John Larkin
Guest

Wed Feb 13, 2019 7:45 am

On Tue, 12 Feb 2019 15:12:11 -0800 (PST), RichD
<r_delaney2001_at_yahoo.com> wrote:

Quote:
On February 12, John Larkin wrote:
Looking at network theory and the duality theorems,
why is there no mutual capacitance? i.e. electric
flux linkages, symmetric to mutual inductance and B flux.

There are two commonly given values for the capacitance between the
earth and the moon, 160uF and 3 uF. I think one is 2-wire capacitance
and the smaller one is 3-wire.

2-wire, 3-wire?

https://www.dropbox.com/s/ir45h6qd8gjryl0/2wire_3wire.JPG?dl=0

The 3-wire measurement ignores Cy and Cz.

If the moon moved away from earth, Cem would approach zero, but Ceu
and Cmu wouldn't change.

Most good c-meters will do 3-wire measurement, which allows a small
cap to be measured at the ends of coaxial cables.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

John Larkin
Guest

Wed Feb 13, 2019 7:45 am

On Tue, 12 Feb 2019 17:55:41 -0800 (PST), George Herold
<gherold_at_teachspin.com> wrote:

Quote:
On Tuesday, February 12, 2019 at 10:33:40 AM UTC-5, Phil Hobbs wrote:
On 2/11/19 5:58 PM, RichD wrote:
Looking at network theory and the duality theorems,
why is there no mutual capacitance? i.e. electric
flux linkages, symmetric to mutual inductance and B flux.

--
Rich

There is. It's usually just called 'capacitance', unless you need to
distinguish it from self-capacitance.

A 1-cm radius isolated sphere has a self-capacitance of 1 cm (Gaussian
units), which is about 1.12 pF.
Huh right, I had this picture of three hunks of stuff with various
inter-capacitances. But that starts with one hunk!

George H.

Just get a ball bearing floating in space and throw electrons at it.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

George Herold
Guest

Wed Feb 13, 2019 4:45 pm

On Wednesday, February 13, 2019 at 12:56:49 AM UTC-5, John Larkin wrote:
Quote:
On Tue, 12 Feb 2019 15:12:11 -0800 (PST), RichD
r_delaney2001_at_yahoo.com> wrote:

On February 12, John Larkin wrote:
Looking at network theory and the duality theorems,
why is there no mutual capacitance? i.e. electric
flux linkages, symmetric to mutual inductance and B flux.

There are two commonly given values for the capacitance between the
earth and the moon, 160uF and 3 uF. I think one is 2-wire capacitance
and the smaller one is 3-wire.

2-wire, 3-wire?

https://www.dropbox.com/s/ir45h6qd8gjryl0/2wire_3wire.JPG?dl=0

The 3-wire measurement ignores Cy and Cz.

If the moon moved away from earth, Cem would approach zero, but Ceu
and Cmu wouldn't change.

Most good c-meters will do 3-wire measurement, which allows a small
cap to be measured at the ends of coaxial cables.

OK we should be able to work out the earth-moon capacitance as a
physics problem.
Here it is using method of images.
http://www.iue.tuwien.ac.at/phd/wasshuber/node77.html

(Hmm that is for sphere's of equal radius.)

As a first approximation we could guess that the Earth's C to the
universe is decreased by the ratio of the field lines that hit the
moon, to all of them... Which is pi*R_moon ^2/ (4*pi*Dist_E-M^2)
R_earth ~6.4 x10^6 m C_earth ~ 640 uF
R_moon ~1.7 x10^6 m
and Dist_E-M ~3.8x10^8 m.

Putting that all in.. and hopefully making no mistakes I get a drcrease
of 5x10^-6 or C_e-m ~3,200 pF .... 3.2 nF
What was your number for C_e-m?

George H.

Of course this is going to only be true at low frequency...
Speed of light and all.

Quote:

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

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elektroda.net NewsGroups Forum Index - Electronic for beginners - mutual capacitance?