Let's Take A Vote...

Objects have both self-capacitance and mutual capacitance, so it's quite sensible to talk about a capacitor with only one lead. In Gaussian units, the self-capacitance of an isolated sphere of radius r centimetres is r. (The CGS unit of capacitance is the centimetre.)

One cm ~= 1.12 pF, so 330,000 pF is about 30 km radius. That's quite a big reel!

Cheers

Phil Hobbs

Yep. Must be black magic :-) ...Jim Thompson

Every step-down DC-DC converter in the world puts out more current than it takes in, as commonly understood in the EE world. Or does your PC have a mondo heatsink on the PSU?

Cheers

Phil Hobbs

Cheers

Phil Hobbs

Of course it does (*). I was being facetious. How did you miss it ?:-)

(*) Thus my tongue-in-cheek post...

"NNTP-Posting-Date: Tue, 20 Jul 2010 10:24:26 -0500 From: Jim Thompson Newsgroups: sci.electronics.design Subject: Charge Conservation - Hint of the Day Date: Tue, 20 Jul 2010 08:24:26 -0700 Message-ID:

Charge Conservation - Hint of the Day:

How many Coulombs can a 1mH inductor charged to 1A deliver?"

Which seems to have gone over everyone's head and created asinine retorts.

Such a "discussion" group... NOT :-(

Nothing but a bunch of prima donnas and bloviators. ...Jim Thompson

Do inductors get "charged" or do they get a field applied to them?

Coils held at a static DC value project a specific field level and density. Release the DC application, and that field collapses, releasing the energy that was holding the core atoms in a forced orientation. The amount of energy such a collapse can deliver has a lot to do with how quickly it saturates under DC excitation. Noting these particulars allows one to characterize the operational parameters of a specific coil or transformer. This is why we choose laminated for low frequency power and smaller domain media for higher frequency, lower power(density) applications. *then* one starts talking about windings and turns and transformational characteristics.

A cap with a coulomb "in it" will eventually deliver it all back out. An inductor, on the other hand, is where a lot of the losses in electronics can be found. They do NOT deliver all they get 'fed'. Sousing an inductor in your ideal circuit should ideally include some of the parasitic effects that they suffer to yield idealized results.

Some things just conjure up problems if idealized absolutely.

I'm terribly sorry about that. Some things are easy to miss in your recent posts, though--actual engineering content, for instance, as opposed to organic waste material. I'm reminded of the famous book review by Moses Hadas: "This book fills a much-needed space." ;)

You claim merely to want to correct error and set the record straight--so why all the junior high school coyness and posturing, rather than just posting a link? Maybe we could all learn something useful.

I've used many of your chips with both profit and pleasure (I used to love the MC1648, for instance), and so have most of the rest of us on SED, so you really don't need to do this to gain respect.

Cheers

Phil Hobbs

=A0 =A0 ...Jim Thompson

=A0 =A0| =A0 =A0mens =A0 =A0 |

=A0 | =A0 =A0 et =A0 =A0 =A0|

=A0|

=A0 =A0 =A0 =A0 |

The charge is on the surface of the balloon. Just like on your CRT surface, it requires a conductive (hand) to actually make contact with the electrons sitting on the surface to 'remove' them into your ground sink body. When you pop the balloon, you literally fling the electrons off that surface. Many remain in the air in the cage, IF it is dry air to start with. Many strike the cage and get absorbed. Some remain on the balloon carcass, whether you noticed it or not, and contact with the carcass does NOT remove the charge from it. It is NON-conductive, remember? Nothing special. A cathode recitfier is a perfect example of doing it with heat and attraction instead of blowing it off with an explosion of air.

I err in trying to taunt youngsters (can't use "young bucks" anymore, John "The Bloviator" Larkin gets sexually aroused :) to think for themselves.

That's the way you really learn, not by having answers served up to you on a platter.

I owe my inquisitiveness and tenacity to one old battle-axe of an 8th grade Algebra teacher, Evelyn Truchovesky, who forced me to think things through on my own. She impressed me so much that I, to this day, use her way of writing a capital "E" for my middle initial.

And then there was a Trigonometry teacher who kept me away by handing me textbook after textbook, "Here! Work all the problems in this book, THEN come discuss them with me." :-)

Glad you like the MC1648! Still popular, but no one making it anymore. Last year I did a custom chip design that, amongst a gezillion other functions, featured two MC1648 equivalents, but on a faster process and with significantly improved AGC. ...Jim Thompson

The entire planet is only about a 700 uF cap, but the voltage rating is pretty good. Bob Pease presided over a debate a few years ago about the capacitance between the earth and the moon; there were two distinct values cited, and he came down on the side of the smaller one and ridiculed the other. I think it depends on whether you do a

I wonder what the net voltage of "ground" is. Since we keep getting whacked with solar wind (net protons?) we might actually be heavily charged. There's a considerable gradient at the surface.

John

--- As is the _mechanical_ force exerted by an electrical charge.

For example, in the post I made from Schaum's, you obviously missed supplemental problem 24 on page 144:

Q. "If two equal charges, each of 1 coulomb, were separated in air by a distance of 1km, what would be the force between them?"

A. "9000 nt repulsion."

---

--- Well, by restating the problem like this: "What two like charges, separated in air by a distance of 1km would cause a repulsive force between them of 9000 nt?" ,it becomes obvious that charge can be a measure of mechanical force since the answer is: "One coulomb each."

As for volts and abvolts, I don't believe there's any question that those are units of _electromotive_ force, do you?

You might read this

since it's the easiest part of the article to understand.

Engineers do sometimes break the rules and add non-commensurable units, like designing a foldback power supply that limits the sum of a voltage and a current. Addition is a poor substitute for multiplication, but it's a lot easier to do with cheap parts.

John

One for the Pommy twit:

for

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arge

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Here, Trickle Charge... this one is for you.

Yes, I know the body model has a ground. But my point was that the human can deliver a static shock without being grounded. Carrying a static charge above (below?) ground.

Grant.

For a 1.2pF sphere? ;^)

Grant.

Engineering is often simply about placing the decimal point in the right spot! :)

Grant.