Let's Take A Vote...
in [Design]
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From: John Larkin on 24 Jul 2010 18:48 On Sun, 25 Jul 2010 07:53:49 +1000, Grant <omg(a)grrr.id.au> wrote: >On Sat, 24 Jul 2010 13:38:23 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>On Sat, 24 Jul 2010 15:14:41 -0400, Phil Hobbs >><pcdhSpamMeSenseless(a)electrooptical.net> wrote: >> >>>Grant wrote: >>>> On Sat, 24 Jul 2010 08:51:58 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>> >>>>> On Sat, 24 Jul 2010 09:45:53 +0100, Martin Brown >>>>> <|||newspam|||@nezumi.demon.co.uk> wrote: >>>>> >>>>>> On 23/07/2010 23:52, Jim Thompson wrote: >>>>>>> Let's Take A Vote... >>>>>>> >>>>>>> While I write this up, hopefully sometime this weekend, let me ask for >>>>>>> votes... >>>>>>> >>>>>>> How many think, as Larkin opines, "charge is not conserved" ?? >>>>>> Hopefully not too many. But it is difficult to predict the behaviour of >>>>>> electronics engineers - about half of them think Einstein was wrong :( >>>>>>> How many think charge IS conserved ?? >>>>>> Just about every physicist on the planet since Ben Franklin. >>>>>> >>>>>> It was the inconsistency of Ampere's Law with conservation of charge >>>>>> that led Maxwell to formulate his famous equations and show that >>>>>> oscillating fields of electromagnetic radiation travel at a constant >>>>>> speed c in a vacuum. >>>>>>> Just curious what I'm up against here. >>>>>>> >>>>>>> ...Jim Thompson >>>>>> A idealised physics version of your original capacitor problem but >>>>>> without the switch can be stated as the following problem: >>>>>> >>>>>> Two identical metal spheres with capacitance C are used. >>>>>> Initially one is uncharged and the other with a charge Q >>>>>> >>>>>> They are brought together from infinity until they touch. >>>>>> >>>>>> Describe what happens and how the charge is distributed after they are >>>>>> in electrical contact. You can add an infinite ground plane under the >>>>>> experiment if it makes you feel better about the circuit analogue. >>>>>> >>>>> Where can I buy 0.33 uF surface-mount metal spheres? Are they >>>>> expensive? I'd need ROHS, of course, on reels. [1] >>>> >>>> Second terminal optional?! >>>> >>>> But then, we sorta cater to 'monopole' charge when using human >>>> body model's charge for anti-static measures. >>>> >>>> Grant. >>>>> John >>>>> >>>>> [1] extra credit: how big would they be? >>>>> >>> >>>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 >> >>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 >>2-terminal or a 3-terminal measurement. One equation approaches zero C >>with distance, the other levels off. >> >>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. > >Net voltage with respect to what? The universe! John
From: Nunya on 24 Jul 2010 18:55 On Jul 24, 3:37 pm, Phil Hobbs <pcdhSpamMeSensel...(a)electrooptical.net> wrote: > John Larkin wrote: > > On Sat, 24 Jul 2010 15:14:41 -0400, Phil Hobbs > > <pcdhSpamMeSensel...(a)electrooptical.net> wrote: > > >> Grant wrote: > >>> On Sat, 24 Jul 2010 08:51:58 -0700, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > > >>>> On Sat, 24 Jul 2010 09:45:53 +0100, Martin Brown > >>>> <|||newspam...(a)nezumi.demon.co.uk> wrote: > > >>>>> On 23/07/2010 23:52, Jim Thompson wrote: > >>>>>> Let's Take A Vote... > > >>>>>> While I write this up, hopefully sometime this weekend, let me ask for > >>>>>> votes... > > >>>>>> How many think, as Larkin opines, "charge is not conserved" ?? > >>>>> Hopefully not too many. But it is difficult to predict the behaviour of > >>>>> electronics engineers - about half of them think Einstein was wrong :( > >>>>>> How many think charge IS conserved ?? > >>>>> Just about every physicist on the planet since Ben Franklin. > > >>>>> It was the inconsistency of Ampere's Law with conservation of charge > >>>>> that led Maxwell to formulate his famous equations and show that > >>>>> oscillating fields of electromagnetic radiation travel at a constant > >>>>> speed c in a vacuum. > >>>>>> Just curious what I'm up against here. > > >>>>>> ...Jim Thompson > >>>>> A idealised physics version of your original capacitor problem but > >>>>> without the switch can be stated as the following problem: > > >>>>> Two identical metal spheres with capacitance C are used. > >>>>> Initially one is uncharged and the other with a charge Q > > >>>>> They are brought together from infinity until they touch. > > >>>>> Describe what happens and how the charge is distributed after they are > >>>>> in electrical contact. You can add an infinite ground plane under the > >>>>> experiment if it makes you feel better about the circuit analogue. > > >>>> Where can I buy 0.33 uF surface-mount metal spheres? Are they > >>>> expensive? I'd need ROHS, of course, on reels. [1] > >>> Second terminal optional?! > > >>> But then, we sorta cater to 'monopole' charge when using human > >>> body model's charge for anti-static measures. > > >>> Grant. > >>>> John > > >>>> [1] extra credit: how big would they be? > > >> 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 > > > 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 > > 2-terminal or a 3-terminal measurement. One equation approaches zero C > > with distance, the other levels off. > > > 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 > > <dim-memory-on> > > The Sun is nearly electrically neutral, because it continuously streams > plasma, which is electrically conductive. If there were any really big > excess charge, there would be an excess of one polarity in the solar > wind until it was dissipated. (There may be some solar processes that > act to maintain a smallish charge on the Sun, but it won't be much.) > > The whole Earth (solid plus atmosphere) is also nearly electrically > neutral, due to being immersed in a conducting medium (the solar wind). > > The solid Earth has a net negative charge of something like 1E10 > coulombs, iirc, and the atmosphere a nearly equal positive charge, > maintained by thunderstorms. (Google will have a better handle on it, I > expect.) > > <dim-memory-off> > > Cheers > > Phil Hobbs > > -- > Dr Philip C D Hobbs > Principal > ElectroOptical Innovations > 55 Orchard Rd > Briarcliff Manor NY 10510 > 845-480-2058 > hobbs at electrooptical dot nethttp://electrooptical.net This is spot on.
From: Nunya on 24 Jul 2010 18:58 On Jul 24, 3:48 pm, Trickle Charge <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > The universe! > John That would make you a new particle. A "Convolutron".
From: m II on 24 Jul 2010 20:36 John Fields wrote: > 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." I like my comb. I brush it with a scarf. Then I hold it close to a thin stream of water coming out of my tap. The water gets deflected in it's fall by a 20 to 40 degree angle. Pretty good mechanical movement due to a static charge. Eventually, dissipation rears it's ugly head and the bent water straightens slowly out. The comb returns to it's drawer, reminiscing of more useful, follicle filled days. mike
From: George Herold on 25 Jul 2010 00:14
On Jul 24, 11:51 am, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Sat, 24 Jul 2010 09:45:53 +0100, Martin Brown > > > > > > <|||newspam...(a)nezumi.demon.co.uk> wrote: > >On 23/07/2010 23:52, Jim Thompson wrote: > >> Let's Take A Vote... > > >> While I write this up, hopefully sometime this weekend, let me ask for > >> votes... > > >> How many think, as Larkin opines, "charge is not conserved" ?? > > >Hopefully not too many. But it is difficult to predict the behaviour of > >electronics engineers - about half of them think Einstein was wrong :( > > >> How many think charge IS conserved ?? > > >Just about every physicist on the planet since Ben Franklin. > > >It was the inconsistency of Ampere's Law with conservation of charge > >that led Maxwell to formulate his famous equations and show that > >oscillating fields of electromagnetic radiation travel at a constant > >speed c in a vacuum. > > >> Just curious what I'm up against here. > > >> ...Jim Thompson > > >A idealised physics version of your original capacitor problem but > >without the switch can be stated as the following problem: > > >Two identical metal spheres with capacitance C are used. > >Initially one is uncharged and the other with a charge Q > > >They are brought together from infinity until they touch. > > >Describe what happens and how the charge is distributed after they are > >in electrical contact. You can add an infinite ground plane under the > >experiment if it makes you feel better about the circuit analogue. > > Where can I buy 0.33 uF surface-mount metal spheres? Are they > expensive? I'd need ROHS, of course, on reels. [1] > > John > "[1] extra credit: how big would they be?" epsilon sub zero times R? or is there a 4*pi in there? 4*pi*epsilon is about 10^-10, so you need a radius of 10^3 meters for 0.1uF, 3.3 kilometers for your desired value.... but I'm going to have to check my math before I can quote you a price. George H. - Hide quoted text - > > - Show quoted text - |