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Post by JohnV on Oct 31, 2016 15:00:18 GMT
Come on Gibbo. Back to basic dimensional analysis. Charge has no energy except in the presence of a voltage gradient. There is electrical charge everywhere but until it is "pumped up" by a voltage gradient it just sits there. Hence a unit of measurement is the MeV or mega electron volt. Energy = Charge x voltage. If the voltage is zero, there is no energy. Agreed. Now explain how you can have an AH with no energy. let's have a go at a serious answer. Surely AH is a potential, there is no energy if there is no current being drawn. It is purely a potential energy. The AH as a potential is not a fixed figure it is dependent entirely on external factors in the way that the energy is removed from the potential source
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Post by Graham on Oct 31, 2016 15:07:07 GMT
Agreed. Now explain how you can have an AH with no energy. let's have a go at a serious answer. Surely AH is a potential, there is no energy if there is no current being drawn. It is purely a potential energy. The AH as a potential is not a fixed figure it is dependent entirely on external factors in the way that the energy is removed from the potential source N has left the hustings. Time for a break
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Post by JohnV on Oct 31, 2016 15:11:30 GMT
let's have a go at a serious answer. Surely AH is a potential, there is no energy if there is no current being drawn. It is purely a potential energy. The AH as a potential is not a fixed figure it is dependent entirely on external factors in the way that the energy is removed from the potential source N has left the hustings. Time for a break Thank Gawd for that ...... I'm afraid my days of thinking quickly through things like this are long gone ..... it takes me a little while to A) get my thoughts straight and B) get my typing straight edit to add .... only the funnies come quickly !!!
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Post by tonyqj on Oct 31, 2016 15:18:28 GMT
N has left the hustings. Time for a break Thank Gawd for that ...... I'm afraid my days of thinking quickly through things like this are long gone ..... it takes me a little while to A) get my thoughts straight and B) get my typing straight edit to add .... only the funnies come quickly !!! Always π Anyway, all the atomic energies calculations are a bit beyond me - but it's fun to watch Gibbo & Nick get into a scrap. Reminds me of the old days with Chris W except Nick tends not to get his maths wrong.
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Post by smileypete on Oct 31, 2016 15:18:52 GMT
Glad we've moved on from bloody Peukert! Peukert = patron saint of waffling battery experts. Anyway Happy Birthday Gibbo. ETA: I think Chris W probably still prays to Peukert every night!
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Post by Graham on Oct 31, 2016 15:19:53 GMT
N has left the hustings. Time for a break Thank Gawd for that ...... I'm afraid my days of thinking quickly through things like this are long gone ..... it takes me a little while to A) get my thoughts straight and B) get my typing straight edit to add .... only the funnies come quickly !!! Interested what Gibbs' definitions are and if brain got anywhere near, so long ago and never used. Not good at funnies, not encouraged as a child
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Post by Gibbo on Oct 31, 2016 17:23:13 GMT
Agreed. Now explain how you can have an AH with no energy. let's have a go at a serious answer. Surely AH is a potential, there is no energy if there is no current being drawn. It is purely a potential energy. The AH as a potential is not a fixed figure it is dependent entirely on external factors in the way that the energy is removed from the potential source No. An amphour is one amp flowing for an hour. Or two amps flowing for half an hour, or 4 amps flowing for 15 minutes etc. That's what it means. Using it to specify a battery capacity tells you how long you can pull x amps from that battery. At a fixed voltage, AH are directly proportional to energy and hence a valid means of measurement. ETA: Yes I know technically amps don't flow, but grammatically the sentences don't work otherwise.
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Post by Gibbo on Oct 31, 2016 17:26:35 GMT
Thank Gawd for that ...... I'm afraid my days of thinking quickly through things like this are long gone ..... it takes me a little while to A) get my thoughts straight and B) get my typing straight edit to add .... only the funnies come quickly !!! Always π Anyway, all the atomic energies calculations are a bit beyond me - but it's fun to watch Gibbo & Nick get into a scrap. Reminds me of the old days with Chris W except Nick tends not to get his maths wrong.
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Post by Telemachus on Oct 31, 2016 17:38:54 GMT
Come on Gibbo. Back to basic dimensional analysis. Charge has no energy except in the presence of a voltage gradient. There is electrical charge everywhere but until it is "pumped up" by a voltage gradient it just sits there. Hence a unit of measurement is the MeV or mega electron volt. Energy = Charge x voltage. If the voltage is zero, there is no energy. Agreed. Now explain how you can have an AH with no energy. AH is just a unit of charge. A coulomb is of course the SI unit. There are 3600 (60x60) coulombs in an AH An amp is 1 coulomb per second (C/s) Electrical power is amps x volts (C/s x V) Electrical energy is power x time (kWh etc) (C/s x V x s) So with the two s cancelling out we have electrical energy = C x V (Hence electron volts etc) If those are the dimensions of electrical energy, and one then sets the voltage to zero, the energy is zero. Consider current flowing round a superconducting ring with zero voltage drop (zero resistance). The power according to I^2R is zero. But the current is still flowing as evidenced by the magnetic field. When you say "how can you have AH with no energy" I think you are getting bogged down with AH as used in batteries to describe their capacity. But consider a lead acid cell, 1AH at ~2v so 2 WH of energy. Now another cell say NiCd with 1AH at 1.2V, so 1.2WH. Now consider an imaginary series if batteries of technologies with increasingly less cell voltage. The stored energy tends to zero. It is just because charge without voltage is so innocuous (having zero energy) that you can't see it.
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Post by Telemachus on Oct 31, 2016 17:42:44 GMT
let's have a go at a serious answer. Surely AH is a potential, there is no energy if there is no current being drawn. It is purely a potential energy. The AH as a potential is not a fixed figure it is dependent entirely on external factors in the way that the energy is removed from the potential source N has left the hustings. Time for a break Sorry, had to go out to Jeff's parents. They'd got an Amazon Fire stick and have spent the last week trying to get it to connect to their wifi. Once I'd removed all the energy from the stick's charge by zeroing the voltage, and then gave it energy by reapplying the voltage to the charge, it worked fine.
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Post by Gibbo on Oct 31, 2016 17:47:37 GMT
Agreed. Now explain how you can have an AH with no energy. AH is just a unit of charge. A coulomb is of course the SI unit. There are 3600 (60x60) coulombs in an AH An amp is 1 coulomb per second (C/s) Electrical power is amps x volts (C/s x V) Electrical energy is power x time (kWh etc) (C/s x V x s) So with the two s cancelling out we have electrical energy = C x V (Hence electron volts etc) If those are the dimensions of electrical energy, and one then sets the voltage to zero, the energy is zero. Consider current flowing round a superconducting ring with zero voltage drop (zero resistance). The power according to I^2R is zero. But the current is still flowing as evidenced by the magnetic field. When you say "how can you have AH with no energy" I think you are getting bogged down with AH as used in batteries to describe their capacity. But consider a lead acid cell, 1AH at ~2v so 2 WH of energy. Now another cell say NiCd with 1AH at 1.2V, so 1.2WH. Now consider an imaginary series if batteries of technologies with increasingly less cell voltage. The stored energy tends to zero. It is just because charge without voltage is so innocuous (having zero energy) that you can't see it. Draw me a circuit which will pass a total of x (pick your own non zero value) amp hours using no energy.
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Post by Telemachus on Oct 31, 2016 17:52:13 GMT
let's have a go at a serious answer. Surely AH is a potential, there is no energy if there is no current being drawn. It is purely a potential energy. The AH as a potential is not a fixed figure it is dependent entirely on external factors in the way that the energy is removed from the potential source No. An amphour is one amp flowing for an hour. Or two amps flowing for half an hour, or 4 amps flowing for 15 minutes etc. That's what it means. Using it to specify a battery capacity tells you how long you can pull x amps from that battery. At a fixed voltage, AH are directly proportional to energy and hence a valid means of measurement. ETA: Yes I know technically amps don't flow, but grammatically the sentences don't work otherwise. An amphour is 3600 coulombs. I think some confusion is arising from the good old English language. So by "charge" I mean the fundamental electrical concept, not charge as in "charging the batteries". By AH I mean the quantity of charge that is 3600 coulombs, not a label on a battery indicating how any coulombs it can push out before going flat. The battery doesn't store all that electrical charge (i.e. it's not like a cylinder of compressed electrons) it merely stores the capability of pushing that amount of charge out of its terminals. But since that capability is by means of an electrochemical reaction, each molecule moving 1 electron, the stored "thing" can only be quoted as charge (AH, normally) - being a measure of the quantity of reactable chemicals - and not as energy. You don't normally see batteries quoted as having a rating in kWH or the like.
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Post by Telemachus on Oct 31, 2016 17:53:08 GMT
AH is just a unit of charge. A coulomb is of course the SI unit. There are 3600 (60x60) coulombs in an AH An amp is 1 coulomb per second (C/s) Electrical power is amps x volts (C/s x V) Electrical energy is power x time (kWh etc) (C/s x V x s) So with the two s cancelling out we have electrical energy = C x V (Hence electron volts etc) If those are the dimensions of electrical energy, and one then sets the voltage to zero, the energy is zero. Consider current flowing round a superconducting ring with zero voltage drop (zero resistance). The power according to I^2R is zero. But the current is still flowing as evidenced by the magnetic field. When you say "how can you have AH with no energy" I think you are getting bogged down with AH as used in batteries to describe their capacity. But consider a lead acid cell, 1AH at ~2v so 2 WH of energy. Now another cell say NiCd with 1AH at 1.2V, so 1.2WH. Now consider an imaginary series if batteries of technologies with increasingly less cell voltage. The stored energy tends to zero. It is just because charge without voltage is so innocuous (having zero energy) that you can't see it. Draw me a circuit which will pass a total of x (pick your own non zero value) amp hours using no energy. Any circuit where the resistance is zero, such as a superconducting ring.
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Post by Gibbo on Oct 31, 2016 17:55:42 GMT
I can't even be bothered with this. You're just being silly.
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Post by bamber on Oct 31, 2016 17:59:21 GMT
Gibbo v Nick, so glad I joined this site, sits back to enjoy the show..... Where's Chris W when you need him ? π
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