Charge Conservation - Hint of the Day
in [Design]
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From: Jim Thompson on 20 Jul 2010 21:14 On Tue, 20 Jul 2010 17:32:12 -0700, Tim Wescott <tim(a)seemywebsite.com> wrote: >On 07/20/2010 09:32 AM, Jim Thompson wrote: >> On Tue, 20 Jul 2010 08:53:22 -0700, Tim Wescott<tim(a)seemywebsite.com> >> wrote: >> >>> On 07/20/2010 08:24 AM, Jim Thompson wrote: >>>> Charge Conservation - Hint of the Day: >>>> >>>> How many Coulombs can a 1mH inductor charged to 1A deliver? >>> >>> That's insufficient information, and I rather expect that you know it. >> >> No. It's provided to cause young bucks to do some thinking. Looks >> like it didn't work with you :-( >> >> (Except that it did annoy Larkin, yet again... so a partial success >> :-) > >Since you didn't answer I have to assume that you couldn't. > >Either this is a trick question, and the answer is "however many excess >electrons it has sitting on it when I hand it to you", or the answer is >"that depends on the coil resistance". > >A 1mH superconducting inductor with 1A will deliver (or flow, if you >want to quibble about the common EE definition of "deliver") an infinite >charge to a dead short, assuming all conductors are also zero resistance. > >Otherwise a 1mH inductor that sees R ohms of total circuit resistance in >the inductor and the load (charge target?) will see it's current decay >as (1A)*e^-(R/L)*t; this will integrate to (1A) * (L/R). So for 1 ohm >total resistance that'd be 1mC, for a 10 ohm total resistance that'd be >100uC, for a 0.1 ohm total resistance it'd be 10mC, etc. > >Answers involving loads that aren't purely resistive are more >complicated, but still obvious if you can understand the above. > >But to answer how much charge that 1mH inductor _can possibly_ deliver >when it has 1A flowing through it depends on the particular inductor's >winding resistance and possibly also on whether it's really a 1mH >inductor when it has 1A flowing through it. > >You may want to pop over to the closest ASU campus that presents EEE 202 >and see if you can audit the course. This problem is no great mystery >for someone who's gotten through sophomore electronics engineering. Sheeeesh, Tim! Did I hit a nerve? I can teach anything over there. My first month in AZ I stood up in an ASU graduate school class and asked, "When do you plan to start teaching this course on a college level?" Got tossed. 10 minutes later (after the Dean and I had a "discussion") I had full credit for the course. I posed the Inductor Question as a mind teaser. Looks like you need to quaff a few... don't be so uptight ;-) This group has really gone to hell... like Democrats... "discussion" allowed only if you kiss up to "The Bloviator". ...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 |
From: Jim Thompson on 20 Jul 2010 21:15 On Tue, 20 Jul 2010 19:36:22 -0500, John Fields <jfields(a)austininstruments.com> wrote: >On Tue, 20 Jul 2010 08:24:26 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote: > >>Charge Conservation - Hint of the Day: >> >>How many Coulombs can a 1mH inductor charged to 1A deliver? > >--- >Well, let's see... > >Since the collapsing magnetic field around an ideal one henry inductor >with one ampere of current in it will deliver about 6.24e18 electrons >into any load when its current source is abruptly terminated, a one >millihenry coil, under the same conditions, should deliver about about >three orders of magnitude less, about one millicoulomb. > >JF Please, John Fields, Please don't shoot from the hip :-) ...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 |
From: John Larkin on 20 Jul 2010 21:35 On Tue, 20 Jul 2010 16:25:40 -0700 (PDT), Richard Henry <pomerado(a)hotmail.com> wrote: >On Jul 20, 2:04�pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)On-My- >Web-Site.com> wrote: >> On Tue, 20 Jul 2010 08:58:13 -0700, John Larkin >> >> >> >> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >On Tue, 20 Jul 2010 08:53:22 -0700, Tim Wescott <t...(a)seemywebsite.com> >> >wrote: >> >> >>On 07/20/2010 08:24 AM, Jim Thompson wrote: >> >>> Charge Conservation - Hint of the Day: >> >> >>> How many Coulombs can a 1mH inductor charged to 1A deliver? >> >> >>That's insufficient information, and I rather expect that you know it. >> >> >He promised us, a couple of weeks ago, a "mathematical proof" of >> >something or other charge related. Is this lame snarky "hint" the best >> >he's been able to come up with? >> >> >John >> >> Cluck! Cluck! Cluck! Cluck! ESAD! >> >> I may be a snarky ol' git, but I'm GOOD ;-) >> >> I'm a graphical/pictorial sort of guy... >> >> Normally I'd do this sort of thing on a white board, before an >> audience at one of my seminars, only an outline in front of me, then >> "play" the audience. >> >> So I've been struggling to create the pictorial on a series of sheets >> of paper to properly describe (and solve the issue). >> >> It's funny, the only time I've had time to think this through has been >> while sitting in doctors' waiting rooms. �This morning, at >> Barnet-Dulaney (wife's eyes, YAG lasers, cataracts), I fitted the >> pictorial together in my head. >> >> Within the next 48 hours you, John "The Bloviator" Larkin (and ALL >> your supplicants) are going to be BURNED AT THE STAKE... >> >> One-by-one every one of your STUPID STUPID STUPID statements will be >> refuted (message ID's supplied to prove you made the STUPID STUPID >> STUPID statements). >> >> I'm working now on how to distribute the material so that it can't be >> disseminated, so that everyone can have a good laugh... BEHIND YOUR >> WORTHLESS BACK ;-) >> >> RECANT! �RECANT! �THE END IS NEAR :-) >> >Is this the way your seminars end? This is more like the way his life will end. Paranoid ravings. John
From: Jim Thompson on 20 Jul 2010 21:38 On Tue, 20 Jul 2010 18:35:04 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Tue, 20 Jul 2010 16:25:40 -0700 (PDT), Richard Henry ><pomerado(a)hotmail.com> wrote: > >>On Jul 20, 2:04�pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)On-My- >>Web-Site.com> wrote: >>> On Tue, 20 Jul 2010 08:58:13 -0700, John Larkin >>> >>> >>> >>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >>> >On Tue, 20 Jul 2010 08:53:22 -0700, Tim Wescott <t...(a)seemywebsite.com> >>> >wrote: >>> >>> >>On 07/20/2010 08:24 AM, Jim Thompson wrote: >>> >>> Charge Conservation - Hint of the Day: >>> >>> >>> How many Coulombs can a 1mH inductor charged to 1A deliver? >>> >>> >>That's insufficient information, and I rather expect that you know it. >>> >>> >He promised us, a couple of weeks ago, a "mathematical proof" of >>> >something or other charge related. Is this lame snarky "hint" the best >>> >he's been able to come up with? >>> >>> >John >>> >>> Cluck! Cluck! Cluck! Cluck! ESAD! >>> >>> I may be a snarky ol' git, but I'm GOOD ;-) >>> >>> I'm a graphical/pictorial sort of guy... >>> >>> Normally I'd do this sort of thing on a white board, before an >>> audience at one of my seminars, only an outline in front of me, then >>> "play" the audience. >>> >>> So I've been struggling to create the pictorial on a series of sheets >>> of paper to properly describe (and solve the issue). >>> >>> It's funny, the only time I've had time to think this through has been >>> while sitting in doctors' waiting rooms. �This morning, at >>> Barnet-Dulaney (wife's eyes, YAG lasers, cataracts), I fitted the >>> pictorial together in my head. >>> >>> Within the next 48 hours you, John "The Bloviator" Larkin (and ALL >>> your supplicants) are going to be BURNED AT THE STAKE... >>> >>> One-by-one every one of your STUPID STUPID STUPID statements will be >>> refuted (message ID's supplied to prove you made the STUPID STUPID >>> STUPID statements). >>> >>> I'm working now on how to distribute the material so that it can't be >>> disseminated, so that everyone can have a good laugh... BEHIND YOUR >>> WORTHLESS BACK ;-) >>> >>> RECANT! �RECANT! �THE END IS NEAR :-) >>> >>Is this the way your seminars end? > >This is more like the way his life will end. Paranoid ravings. > >John So sayeth the namby pamby jack-wagon of this group :-) Will you sleep well tonight ?:-) ...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 |
From: John Larkin on 20 Jul 2010 21:42
On Tue, 20 Jul 2010 17:32:12 -0700, Tim Wescott <tim(a)seemywebsite.com> wrote: >On 07/20/2010 09:32 AM, Jim Thompson wrote: >> On Tue, 20 Jul 2010 08:53:22 -0700, Tim Wescott<tim(a)seemywebsite.com> >> wrote: >> >>> On 07/20/2010 08:24 AM, Jim Thompson wrote: >>>> Charge Conservation - Hint of the Day: >>>> >>>> How many Coulombs can a 1mH inductor charged to 1A deliver? >>> >>> That's insufficient information, and I rather expect that you know it. >> >> No. It's provided to cause young bucks to do some thinking. Looks >> like it didn't work with you :-( >> >> (Except that it did annoy Larkin, yet again... so a partial success >> :-) > >Since you didn't answer I have to assume that you couldn't. > >Either this is a trick question, and the answer is "however many excess >electrons it has sitting on it when I hand it to you", or the answer is >"that depends on the coil resistance". > >A 1mH superconducting inductor with 1A will deliver (or flow, if you >want to quibble about the common EE definition of "deliver") an infinite >charge to a dead short, assuming all conductors are also zero resistance. > >Otherwise a 1mH inductor that sees R ohms of total circuit resistance in >the inductor and the load (charge target?) will see it's current decay >as (1A)*e^-(R/L)*t; this will integrate to (1A) * (L/R). So for 1 ohm >total resistance that'd be 1mC, for a 10 ohm total resistance that'd be >100uC, for a 0.1 ohm total resistance it'd be 10mC, etc. Dumping that inductor into 1 ohm makes the exact same waveform across the resistor as if you discharged a 1 millifarad cap charged to 1 volt. Ditto 0.001 coulombs. Nice crosscheck. John |