Magic capacitors!
in [Design]
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From: CIC on 4 Aug 2010 21:36 On Thu, 05 Aug 2010 10:27:16 +1000, Grant <omg(a)grrr.id.au> wrote: >On Thu, 5 Aug 2010 00:08:37 +0100, "markp" <map.nospam(a)f2s.com> wrote: > >> >>"Grant" <omg(a)grrr.id.au> wrote in message >>news:s3rj565jd7in972eu9uufgk3cufi9ni444(a)4ax.com... >>> On Wed, 4 Aug 2010 18:13:49 +0100, "markp" <map.nospam(a)f2s.com> wrote: >>> >>>> >>>>"John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in >>>>message >>>>news:6ese46h8ne8luliofpjilue4af6d514js1(a)4ax.com... >>>>> On Wed, 21 Jul 2010 16:30:20 -0500, "George Jefferson" >>>>> <phreon111(a)gmail.com> wrote: >>>>> >>>>>> >>>>>> >>>>>>"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote >>>>>>in >>>>>>message news:rcie465itdu34iaajm1itdqslepu2i87r6(a)4ax.com... >>>>>>> On Wed, 21 Jul 2010 12:14:04 -0700, John Larkin >>>>>>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>>>>> >>>>>>>>On Wed, 21 Jul 2010 12:17:41 -0500, "George Jefferson" >>>>>>>><phreon111(a)gmail.com> wrote: >>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>>"John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in >>>>>>>>>message >>>>>>>>>news:dj7e465sga7fe3nq7hfl3f0uk601pvrem8(a)4ax.com... >>>>>>>>>> On Wed, 21 Jul 2010 11:19:31 -0500, "George Jefferson" >>>>>>>>>> <phreon111(a)gmail.com> wrote: >>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>>"John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in >>>>>>>>>>>message >>>>>>>>>>>news:s43e46la1p1vt11527eg3ptl9ulm44dfrj(a)4ax.com... >>>>>>>>>>>> On Wed, 21 Jul 2010 07:54:03 -0500, "George Jefferson" >>>>>>>>>>>> <phreon111(a)gmail.com> wrote: >>>>>>>>>>>> >>>>>>>>>>>>>Suppose you have two capacitors connected as >>>>>>>>>>>>> >>>>>>>>>>>>>--*-- >>>>>>>>>>>>>| | >>>>>>>>>>>>>C1 C2 >>>>>>>>>>>>>| | >>>>>>>>>>>>>----- >>>>>>>>>>>>> >>>>>>>>>>>>>where * is a switch. >>>>>>>>>>>>> >>>>>>>>>>>>>What is the total energy before and after the switch is closed(in >>>>>>>>>>>>>general). >>>>>>>>>>>> >>>>>>>>>>>> Energy is conserved, so it's the same, if you account for all the >>>>>>>>>>>> manifestations of energy. >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>>You didn't answer the question. I assume this because you don't >>>>>>>>>>>know. >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> State the question unambiguously and I will. >>>>>>>>>> >>>>>>>>>> As I said, the puzzle is both ancient and trivial, so probably JT >>>>>>>>>> invented it. There are web sites and even academic papers devoted >>>>>>>>>> to >>>>>>>>>> it. Given all that, how could I not understand it? >>>>>>>>>> >>>>>>>>> >>>>>>>>>Um you don't get it. Your ignorance in basic electronics amazes me. >>>>>>>> >>>>>>>>That's funny. But people can choose to be amazed in all sorts of ways. >>>>>>>> >>>>>>>> >>>>>>>> Michael >>>>>>>>>got it(although he didn't explain where the energy went but I think >>>>>>>>>gets >>>>>>>>>it). >>>>>>>>> >>>>>>>>>Assume the second cap is initially "uncharged" and has the same >>>>>>>>>capacitance >>>>>>>>>as the first. >>>>>>>>> >>>>>>>>>Then the initial energy is >>>>>>>>> >>>>>>>>>Wi = 1/2*C*V^2 >>>>>>>>>Wf = 2*1/2*C*(V/2)^2 = 1/4*C*V^2 = 1/2*Wi >>>>>>>>> >>>>>>>>>Hence the final energy of the system 1/2 what we started with. >>>>>>>> >>>>>>>>Miraculous calculation. Yours and about 300 web sites that admire this >>>>>>>>puzzle. >>>>>>>> >>>>>>>>You didn't wxplain where the energy went - see those 300 web sites - >>>>>>>>but you are assuming losses. Another solution is that no energy is >>>>>>>>lost, and it rings forever, in which case the final state that you >>>>>>>>cite never happens. The exact waveforms are actually interesting. >>>>>>>> >>>>>>>>> >>>>>>>>>I'd really like to hear your explanation but I know thats >>>>>>>>>impossible(as >>>>>>>>>you'll steal someone elses). After all your the one that believes >>>>>>>>>charge >>>>>>>>>isn't conserved... heres your change to *prove* it. >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>> >>>>>>>>Check my previous posts. I noted the exact waveform across a resistive >>>>>>>>switch, for any values of C1 and C2, and an independent way to compute >>>>>>>>the energy lost in that switch. >>>>>>>> >>>>>>>>Given an inductor, one can move all the energy from one charged cap to >>>>>>>>another, uncharged one. If the C values are unequal, the C*V (charge) >>>>>>>>on the first cap obviously becomes a different C*V on the second one. >>>>>>>>I noted that here some weeks ago, too. >>>>>>>> >>>>>>>>This is all EE101 stuff. >>>>>>>> >>>>>>>>John >>>>>>> >>>>>>> Let the hedging begin... >>>>>>> >>>>>>> In Message-ID: <3b893612tjjndo8o4v1evro050nonjgp41(a)4ax.com> >>>>>>> >>>>>>> You said: >>>>>>> >>>>>>> "Right. If you dump all the energy from one charged cap into another, >>>>>>> discharged, cap of a different value, and do it efficiently, charge is >>>>>>> not conserved." >>>>>>> >>>>>>> Note the NOT CONSERVED. >>>>>>> >>>>>>> Now you say, "...the C*V (charge) on the first cap obviously becomes a >>>>>>> different C*V on the second one". >>>>>>> >>>>>>> Where did the charge come from/go to? >>>>>>> >>>>>>> John "The Bloviator" Larkin is totally incapable of admitting error. >>>>>>> >>>>>>> I truly suspect you're too ignorant to understand :-( >>>>>>> >>>>>> >>>>>>I'm glad my post got what it was suppose to get out. I kinda feel like >>>>>>Breitbart. >>>>>> >>>>> >>>>> Initial condition: >>>>> >>>>> C1 2F, 1 volt, 1 joule, 2 coulombs >>>>> >>>>> C2 1F, 0 volts, 0 joules, 0 coulombs >>>>> >>>>> Now remove all the energy from C1 and deliver it to C2. An inductor >>>>> will move the energy nicely. >>>>> >>>>> Now >>>>> >>>>> C1 has 0 volts, 0 joules, 0 coulombs >>>>> >>>>> C2 has 1.414 volts, 1 joule, 1.414 coulombs. >>>>> >>>>> John >>>> >>>>Sorry but I'm afraid you've fallen into the 'capacitor stores charge' trap >>>>John. It doesn't, as I said in another post, capacitors don't store >>>>charge, >>>>the plates are equal and opposite in the excess or depletion of electrons >>>>(they can't store electrical charge, since we all know the current going >>>>in >>>>and the current coming out of a capacitor is equal, and current is >>>>Coulombs >>>>per second). The total stored electrical charge in a capacitor is zero. >>>>That >>>>negates the whole premise of this analysis. >>>> >>>>Mark. >>> >>> Charge 1uF to 50V and put your tongue across the terminals, now tell me >>> there's nothing there ;) >>> >>> Grant. >> >>I didn't say a capacitor can't store energy, it certainly can. When you say >>'charge 1uF to 50V' the 'charge' bit refers to putting energy into the >>capacitor, not electrical charge. When you put your tongue across the >>terminals you form an electrical circuit, the plate with excess electrons >>pushes electrons through the tongue and the plate with a depletion of >>electrons sucks exactly the same number of electrons back in. The capacitor >>at the end of that 'discharge' cycle has the same number of electrons in it >>as it had when it was 'charged'. > >Practical users of caps use the terms charge and discharge without >qualification. Same as they accept electricity flows from positive >to negative ;) Convention, or convenient lies? Does it matter? > >Grant. P1. OK has been fun reading all this but I give up! I will let you know a secret. We know nothing! The more we learn, the less we know. Why? Let's look at this logically. The universe is infinite and hence its laws and the achievable knowledge is infinite. At this stage our knowledge is insignificant. Welcome to the classroom kiddies!
From: markp on 4 Aug 2010 21:40 "John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message news:ci3k56d0kga1776gghosaq09q2e0i2ahhq(a)4ax.com... > On Wed, 4 Aug 2010 16:55:16 +0100, "markp" <map.nospam(a)f2s.com> wrote: > >> >>"John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in >>message >>news:2vge46h4sragrk4jdn6sasde6hg2r52nos(a)4ax.com... >>> On Wed, 21 Jul 2010 12:17:41 -0500, "George Jefferson" >>> <phreon111(a)gmail.com> wrote: >>> >>>> >>>> >>>>"John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in >>>>message >>>>news:dj7e465sga7fe3nq7hfl3f0uk601pvrem8(a)4ax.com... >>>>> On Wed, 21 Jul 2010 11:19:31 -0500, "George Jefferson" >>>>> <phreon111(a)gmail.com> wrote: >>>>> >>>>>> >>>>>> >>>>>>"John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in >>>>>>message >>>>>>news:s43e46la1p1vt11527eg3ptl9ulm44dfrj(a)4ax.com... >>>>>>> On Wed, 21 Jul 2010 07:54:03 -0500, "George Jefferson" >>>>>>> <phreon111(a)gmail.com> wrote: >>>>>>> >>>>>>>>Suppose you have two capacitors connected as >>>>>>>> >>>>>>>>--*-- >>>>>>>>| | >>>>>>>>C1 C2 >>>>>>>>| | >>>>>>>>----- >>>>>>>> >>>>>>>>where * is a switch. >>>>>>>> >>>>>>>>What is the total energy before and after the switch is closed(in >>>>>>>>general). >>>>>>> >>>>>>> Energy is conserved, so it's the same, if you account for all the >>>>>>> manifestations of energy. >>>>>>> >>>>>> >>>>>>You didn't answer the question. I assume this because you don't know. >>>>>> >>>>> >>>>> State the question unambiguously and I will. >>>>> >>>>> As I said, the puzzle is both ancient and trivial, so probably JT >>>>> invented it. There are web sites and even academic papers devoted to >>>>> it. Given all that, how could I not understand it? >>>>> >>>> >>>>Um you don't get it. Your ignorance in basic electronics amazes me. >>> >>> That's funny. But people can choose to be amazed in all sorts of ways. >>> >>> >>> Michael >>>>got it(although he didn't explain where the energy went but I think gets >>>>it). >>>> >>>>Assume the second cap is initially "uncharged" and has the same >>>>capacitance >>>>as the first. >>>> >>>>Then the initial energy is >>>> >>>>Wi = 1/2*C*V^2 >>>>Wf = 2*1/2*C*(V/2)^2 = 1/4*C*V^2 = 1/2*Wi >>>> >>>>Hence the final energy of the system 1/2 what we started with. >>> >>> Miraculous calculation. Yours and about 300 web sites that admire this >>> puzzle. >>> >>> You didn't wxplain where the energy went - see those 300 web sites - >>> but you are assuming losses. Another solution is that no energy is >>> lost, and it rings forever, in which case the final state that you >>> cite never happens. The exact waveforms are actually interesting. >>> >>>> >>>>I'd really like to hear your explanation but I know thats impossible(as >>>>you'll steal someone elses). After all your the one that believes charge >>>>isn't conserved... heres your change to *prove* it. >>>> >>>> >>>> >>> >>> Check my previous posts. I noted the exact waveform across a resistive >>> switch, for any values of C1 and C2, and an independent way to compute >>> the energy lost in that switch. >>> >>> Given an inductor, one can move all the energy from one charged cap to >>> another, uncharged one. If the C values are unequal, the C*V (charge) >>> on the first cap obviously becomes a different C*V on the second one. >>> I noted that here some weeks ago, too. >>> >>> This is all EE101 stuff. >>> >>> John >> >>Yes, Q=CV equation is somewhat misleading in this context. A capacitor >>doesn't store electrical charge, it stores energy. This is a very common >>misconception, when we say 'charge a capacitor' we don't mean put >>electrical >>charge into it, we mean put energy into it. The plates are equal and >>opposite in electrical charge due to an abundance of electrons on one >>plate >>and an equal and opposite charge on the other. The total stored electrical >>charge in a capacitor is zero, and the Q=CV equation relates to how much >>charge flowed *in and out* of the capacitor (in fact since electrons can't >>cross the barrier between the plates, it actually describes the *modulus* >>of >>the abundance of charge on each plate, one abundance is positive and the >>other is negative). >> >>Mark. >> > > That's not what they taught us in college, and that's not the way we > do engineering. We say that a capacitor stores charge, the amount > being C*V in coulombs, and it works. My whole point, which has evoked > such ranting, is that when you use this convention, be careful about > designing using the concept that (this kind of) charge is always > conserved. > > John > With all due respect, we don't, and shouldn't, say a capacitor 'stores charge'. The misconception comes from the use of the word charge when talking about putting energy into a capacitor, and more explictly the significant lack of clarification given on this when being taught. This is compounded by a confusion of the q=C*V equation which actually relates to the charge on the plates, but one of the plates is of the same value but opposite in polarity, so the sum of those is zero. This is an extremely popular misunderstanding unfortunately, and leads to conclusions that electrical charge is not conserved. In fact, in a closed system where no electrical charge can get in or out, within that system electrical charge *is* conserved, it's actually a fundamental law of physics (along with conservation of energy and momentum, again for closed systems). The same current flows in and out of a capacitor when it is being 'charged' (I assume you are not going to deny that). Note I said the same current, but they are not made of the same electrons because those can't cross the plate barrier. The same amount of electrical charge that goes in comes right out again. How can the capacitor possibly end up with a net charge in it? If it can, where has the electrical charge come from? Have electrons just been conjured up out of nowhere? Mark.
From: Jim Thompson on 4 Aug 2010 21:41 On Wed, 04 Aug 2010 18:08:21 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Wed, 4 Aug 2010 16:55:16 +0100, "markp" <map.nospam(a)f2s.com> wrote: > >> [snip] >> >>Yes, Q=CV equation is somewhat misleading in this context. A capacitor >>doesn't store electrical charge, it stores energy. This is a very common >>misconception, when we say 'charge a capacitor' we don't mean put electrical >>charge into it, we mean put energy into it. The plates are equal and >>opposite in electrical charge due to an abundance of electrons on one plate >>and an equal and opposite charge on the other. The total stored electrical >>charge in a capacitor is zero, and the Q=CV equation relates to how much >>charge flowed *in and out* of the capacitor (in fact since electrons can't >>cross the barrier between the plates, it actually describes the *modulus* of >>the abundance of charge on each plate, one abundance is positive and the >>other is negative). >> >>Mark. >> > >That's not what they taught us in college, and that's not the way we >do engineering. We say that a capacitor stores charge, the amount >being C*V in coulombs, and it works. My whole point, which has evoked >such ranting, is that when you use this convention, be careful about >designing using the concept that (this kind of) charge is always >conserved. > >John What a hoot !-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Spice is like a sports car... Performance only as good as the person behind the wheel.
From: CIC on 4 Aug 2010 21:46 On Wed, 04 Aug 2010 18:00:20 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Thu, 05 Aug 2010 08:41:59 +1000, Grant <omg(a)grrr.id.au> wrote: > >>On Wed, 4 Aug 2010 18:13:49 +0100, "markp" <map.nospam(a)f2s.com> wrote: >> >>> >>>"John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message >>>news:6ese46h8ne8luliofpjilue4af6d514js1(a)4ax.com... >>>> On Wed, 21 Jul 2010 16:30:20 -0500, "George Jefferson" >>>> <phreon111(a)gmail.com> wrote: >>>> >>>>> >>>>> >>>>>"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote >>>>>in >>>>>message news:rcie465itdu34iaajm1itdqslepu2i87r6(a)4ax.com... >>>>>> On Wed, 21 Jul 2010 12:14:04 -0700, John Larkin >>>>>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>>>> >>>>>>>On Wed, 21 Jul 2010 12:17:41 -0500, "George Jefferson" >>>>>>><phreon111(a)gmail.com> wrote: >>>>>>> >>>>>>>> >>>>>>>> >>>>>>>>"John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in >>>>>>>>message >>>>>>>>news:dj7e465sga7fe3nq7hfl3f0uk601pvrem8(a)4ax.com... >>>>>>>>> On Wed, 21 Jul 2010 11:19:31 -0500, "George Jefferson" >>>>>>>>> <phreon111(a)gmail.com> wrote: >>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>>"John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in >>>>>>>>>>message >>>>>>>>>>news:s43e46la1p1vt11527eg3ptl9ulm44dfrj(a)4ax.com... >>>>>>>>>>> On Wed, 21 Jul 2010 07:54:03 -0500, "George Jefferson" >>>>>>>>>>> <phreon111(a)gmail.com> wrote: >>>>>>>>>>> >>>>>>>>>>>>Suppose you have two capacitors connected as >>>>>>>>>>>> >>>>>>>>>>>>--*-- >>>>>>>>>>>>| | >>>>>>>>>>>>C1 C2 >>>>>>>>>>>>| | >>>>>>>>>>>>----- >>>>>>>>>>>> >>>>>>>>>>>>where * is a switch. >>>>>>>>>>>> >>>>>>>>>>>>What is the total energy before and after the switch is closed(in >>>>>>>>>>>>general). >>>>>>>>>>> >>>>>>>>>>> Energy is conserved, so it's the same, if you account for all the >>>>>>>>>>> manifestations of energy. >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>>You didn't answer the question. I assume this because you don't know. >>>>>>>>>> >>>>>>>>> >>>>>>>>> State the question unambiguously and I will. >>>>>>>>> >>>>>>>>> As I said, the puzzle is both ancient and trivial, so probably JT >>>>>>>>> invented it. There are web sites and even academic papers devoted to >>>>>>>>> it. Given all that, how could I not understand it? >>>>>>>>> >>>>>>>> >>>>>>>>Um you don't get it. Your ignorance in basic electronics amazes me. >>>>>>> >>>>>>>That's funny. But people can choose to be amazed in all sorts of ways. >>>>>>> >>>>>>> >>>>>>> Michael >>>>>>>>got it(although he didn't explain where the energy went but I think >>>>>>>>gets >>>>>>>>it). >>>>>>>> >>>>>>>>Assume the second cap is initially "uncharged" and has the same >>>>>>>>capacitance >>>>>>>>as the first. >>>>>>>> >>>>>>>>Then the initial energy is >>>>>>>> >>>>>>>>Wi = 1/2*C*V^2 >>>>>>>>Wf = 2*1/2*C*(V/2)^2 = 1/4*C*V^2 = 1/2*Wi >>>>>>>> >>>>>>>>Hence the final energy of the system 1/2 what we started with. >>>>>>> >>>>>>>Miraculous calculation. Yours and about 300 web sites that admire this >>>>>>>puzzle. >>>>>>> >>>>>>>You didn't wxplain where the energy went - see those 300 web sites - >>>>>>>but you are assuming losses. Another solution is that no energy is >>>>>>>lost, and it rings forever, in which case the final state that you >>>>>>>cite never happens. The exact waveforms are actually interesting. >>>>>>> >>>>>>>> >>>>>>>>I'd really like to hear your explanation but I know thats impossible(as >>>>>>>>you'll steal someone elses). After all your the one that believes >>>>>>>>charge >>>>>>>>isn't conserved... heres your change to *prove* it. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>> >>>>>>>Check my previous posts. I noted the exact waveform across a resistive >>>>>>>switch, for any values of C1 and C2, and an independent way to compute >>>>>>>the energy lost in that switch. >>>>>>> >>>>>>>Given an inductor, one can move all the energy from one charged cap to >>>>>>>another, uncharged one. If the C values are unequal, the C*V (charge) >>>>>>>on the first cap obviously becomes a different C*V on the second one. >>>>>>>I noted that here some weeks ago, too. >>>>>>> >>>>>>>This is all EE101 stuff. >>>>>>> >>>>>>>John >>>>>> >>>>>> Let the hedging begin... >>>>>> >>>>>> In Message-ID: <3b893612tjjndo8o4v1evro050nonjgp41(a)4ax.com> >>>>>> >>>>>> You said: >>>>>> >>>>>> "Right. If you dump all the energy from one charged cap into another, >>>>>> discharged, cap of a different value, and do it efficiently, charge is >>>>>> not conserved." >>>>>> >>>>>> Note the NOT CONSERVED. >>>>>> >>>>>> Now you say, "...the C*V (charge) on the first cap obviously becomes a >>>>>> different C*V on the second one". >>>>>> >>>>>> Where did the charge come from/go to? >>>>>> >>>>>> John "The Bloviator" Larkin is totally incapable of admitting error. >>>>>> >>>>>> I truly suspect you're too ignorant to understand :-( >>>>>> >>>>> >>>>>I'm glad my post got what it was suppose to get out. I kinda feel like >>>>>Breitbart. >>>>> >>>> >>>> Initial condition: >>>> >>>> C1 2F, 1 volt, 1 joule, 2 coulombs >>>> >>>> C2 1F, 0 volts, 0 joules, 0 coulombs >>>> >>>> Now remove all the energy from C1 and deliver it to C2. An inductor >>>> will move the energy nicely. >>>> >>>> Now >>>> >>>> C1 has 0 volts, 0 joules, 0 coulombs >>>> >>>> C2 has 1.414 volts, 1 joule, 1.414 coulombs. >>>> >>>> John >>> >>>Sorry but I'm afraid you've fallen into the 'capacitor stores charge' trap >>>John. It doesn't, as I said in another post, capacitors don't store charge, >>>the plates are equal and opposite in the excess or depletion of electrons >>>(they can't store electrical charge, since we all know the current going in >>>and the current coming out of a capacitor is equal, and current is Coulombs >>>per second). The total stored electrical charge in a capacitor is zero. That >>>negates the whole premise of this analysis. >>> >>>Mark. >> >>Charge 1uF to 50V and put your tongue across the terminals, now tell me >>there's nothing there ;) >> >>Grant. >>> > >Right. And battery chargers are an elaborate public fraud, since >batteries don't store charge. > >And power mosfet data sheets are all wrong. > >John > I don't see how this applies to my flux capacitor though... http://kalecoauto.com/index.php?main_page=product_info&cPath=6&products_id=28
From: Nunya on 4 Aug 2010 22:35
On Aug 4, 5:27 pm, Grant <o...(a)grrr.id.au> wrote: > On Thu, 5 Aug 2010 00:08:37 +0100, "markp" <map.nos...(a)f2s.com> wrote: > > >"Grant" <o...(a)grrr.id.au> wrote in message > >news:s3rj565jd7in972eu9uufgk3cufi9ni444(a)4ax.com... > >> On Wed, 4 Aug 2010 18:13:49 +0100, "markp" <map.nos...(a)f2s.com> wrote: > > >>>"John Larkin" <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote in > >>>message > >>>news:6ese46h8ne8luliofpjilue4af6d514js1(a)4ax.com... > >>>> On Wed, 21 Jul 2010 16:30:20 -0500, "George Jefferson" > >>>> <phreon...(a)gmail.com> wrote: > > >>>>>"Jim Thompson" <To-Email-Use-The-Envelope-I...(a)On-My-Web-Site.com> wrote > >>>>>in > >>>>>messagenews:rcie465itdu34iaajm1itdqslepu2i87r6(a)4ax.com... > >>>>>> On Wed, 21 Jul 2010 12:14:04 -0700, John Larkin > >>>>>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > > >>>>>>>On Wed, 21 Jul 2010 12:17:41 -0500, "George Jefferson" > >>>>>>><phreon...(a)gmail.com> wrote: > > >>>>>>>>"John Larkin" <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote in > >>>>>>>>message > >>>>>>>>news:dj7e465sga7fe3nq7hfl3f0uk601pvrem8(a)4ax.com... > >>>>>>>>> On Wed, 21 Jul 2010 11:19:31 -0500, "George Jefferson" > >>>>>>>>> <phreon...(a)gmail.com> wrote: > > >>>>>>>>>>"John Larkin" <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote in > >>>>>>>>>>message > >>>>>>>>>>news:s43e46la1p1vt11527eg3ptl9ulm44dfrj(a)4ax.com... > >>>>>>>>>>> On Wed, 21 Jul 2010 07:54:03 -0500, "George Jefferson" > >>>>>>>>>>> <phreon...(a)gmail.com> wrote: > > >>>>>>>>>>>>Suppose you have two capacitors connected as > > >>>>>>>>>>>>--*-- > >>>>>>>>>>>>| | > >>>>>>>>>>>>C1 C2 > >>>>>>>>>>>>| | > >>>>>>>>>>>>----- > > >>>>>>>>>>>>where * is a switch. > > >>>>>>>>>>>>What is the total energy before and after the switch is closed(in > >>>>>>>>>>>>general). > > >>>>>>>>>>> Energy is conserved, so it's the same, if you account for all the > >>>>>>>>>>> manifestations of energy. > > >>>>>>>>>>You didn't answer the question. I assume this because you don't > >>>>>>>>>>know. > > >>>>>>>>> State the question unambiguously and I will. > > >>>>>>>>> As I said, the puzzle is both ancient and trivial, so probably JT > >>>>>>>>> invented it. There are web sites and even academic papers devoted > >>>>>>>>> to > >>>>>>>>> it. Given all that, how could I not understand it? > > >>>>>>>>Um you don't get it. Your ignorance in basic electronics amazes me. > > >>>>>>>That's funny. But people can choose to be amazed in all sorts of ways. > > >>>>>>> Michael > >>>>>>>>got it(although he didn't explain where the energy went but I think > >>>>>>>>gets > >>>>>>>>it). > > >>>>>>>>Assume the second cap is initially "uncharged" and has the same > >>>>>>>>capacitance > >>>>>>>>as the first. > > >>>>>>>>Then the initial energy is > > >>>>>>>>Wi = 1/2*C*V^2 > >>>>>>>>Wf = 2*1/2*C*(V/2)^2 = 1/4*C*V^2 = 1/2*Wi > > >>>>>>>>Hence the final energy of the system 1/2 what we started with. > > >>>>>>>Miraculous calculation. Yours and about 300 web sites that admire this > >>>>>>>puzzle. > > >>>>>>>You didn't wxplain where the energy went - see those 300 web sites - > >>>>>>>but you are assuming losses. Another solution is that no energy is > >>>>>>>lost, and it rings forever, in which case the final state that you > >>>>>>>cite never happens. The exact waveforms are actually interesting. > > >>>>>>>>I'd really like to hear your explanation but I know thats > >>>>>>>>impossible(as > >>>>>>>>you'll steal someone elses). After all your the one that believes > >>>>>>>>charge > >>>>>>>>isn't conserved... heres your change to *prove* it. > > >>>>>>>Check my previous posts. I noted the exact waveform across a resistive > >>>>>>>switch, for any values of C1 and C2, and an independent way to compute > >>>>>>>the energy lost in that switch. > > >>>>>>>Given an inductor, one can move all the energy from one charged cap to > >>>>>>>another, uncharged one. If the C values are unequal, the C*V (charge) > >>>>>>>on the first cap obviously becomes a different C*V on the second one. > >>>>>>>I noted that here some weeks ago, too. > > >>>>>>>This is all EE101 stuff. > > >>>>>>>John > > >>>>>> Let the hedging begin... > > >>>>>> In Message-ID: <3b893612tjjndo8o4v1evro050nonjg...(a)4ax.com> > > >>>>>> You said: > > >>>>>> "Right. If you dump all the energy from one charged cap into another, > >>>>>> discharged, cap of a different value, and do it efficiently, charge is > >>>>>> not conserved." > > >>>>>> Note the NOT CONSERVED. > > >>>>>> Now you say, "...the C*V (charge) on the first cap obviously becomes a > >>>>>> different C*V on the second one". > > >>>>>> Where did the charge come from/go to? > > >>>>>> John "The Bloviator" Larkin is totally incapable of admitting error. > > >>>>>> I truly suspect you're too ignorant to understand :-( > > >>>>>I'm glad my post got what it was suppose to get out. I kinda feel like > >>>>>Breitbart. > > >>>> Initial condition: > > >>>> C1 2F, 1 volt, 1 joule, 2 coulombs > > >>>> C2 1F, 0 volts, 0 joules, 0 coulombs > > >>>> Now remove all the energy from C1 and deliver it to C2. An inductor > >>>> will move the energy nicely. > > >>>> Now > > >>>> C1 has 0 volts, 0 joules, 0 coulombs > > >>>> C2 has 1.414 volts, 1 joule, 1.414 coulombs. > > >>>> John > > >>>Sorry but I'm afraid you've fallen into the 'capacitor stores charge' trap > >>>John. It doesn't, as I said in another post, capacitors don't store > >>>charge, > >>>the plates are equal and opposite in the excess or depletion of electrons > >>>(they can't store electrical charge, since we all know the current going > >>>in > >>>and the current coming out of a capacitor is equal, and current is > >>>Coulombs > >>>per second). The total stored electrical charge in a capacitor is zero.. > >>>That > >>>negates the whole premise of this analysis. > > >>>Mark. > > >> Charge 1uF to 50V and put your tongue across the terminals, now tell me > >> there's nothing there ;) > > >> Grant. > > >I didn't say a capacitor can't store energy, it certainly can. When you say > >'charge 1uF to 50V' the 'charge' bit refers to putting energy into the > >capacitor, not electrical charge. When you put your tongue across the > >terminals you form an electrical circuit, the plate with excess electrons > >pushes electrons through the tongue and the plate with a depletion of > >electrons sucks exactly the same number of electrons back in. The capacitor > >at the end of that 'discharge' cycle has the same number of electrons in it > >as it had when it was 'charged'. > > Practical users of caps use the terms charge and discharge without > qualification. Same as they accept electricity flows from positive > to negative ;) Convention, or convenient lies? Does it matter? > > Grant. If you knew anything about how a crt works, you would know the answer to that question. |