Talk:Ivor Catt/Archive 11

message: The model identifies "current" and "voltage" as distinct, if interrelated, concepts. When you apply this to a distinct "unconstrained" pulse (ie a pulse with definite leading and trailing edges) you get three distinct regions - the bit between the leading and trailing edges, where there is (moving) "charge", and the portions ahead of and behind the pulse where there is no charge. If you look at the pulse in terms of voltage, current and charge, and inductance and capacitance, you will see that the voltage is defined by the the amount of charge held on the capacitor defined by the pulse edges, and that the current is flowing in the inductance that is likewise defined. If, as Catt did, you calculate the energy stored in the capacitance and the inductance you will find them to be equal. Catt extrapolated this equality to a sort of "universal truth", that the energy stored in the electric and magnetic fields are always equal. It is this assertion that underpins his reverberating ("contrapuntal") TEM waves. The "conventional" position is that the equality is merely a property of the TL. (Presumably slowing the current flow increases the charge at that point, which increases the voltage in the capacitance, which tends to increase the current, etc.) I don't think I've seen any of Catt's theorising actually come up with a result that differs from the "conventional" model - basically he is arguing that because he gets the right answer, his model is correct, but he's looked up the answer at the back of the book and has cobbled together the maths to fit. And when the maths and the physics get difficult, he just argues that he is right and everyone else is wrong. -- Kevin Brunt 23:11, 8 March 2006 (UTC)
replies: text: Kevin, There is no electric current in the portion of the logic step where the voltage is constant with distance.  You need to have a voltage gradient with distance to keep the electrons drifting.  Only energy current, not electric current, is possible if the voltage is constant with distance along a conductor.  There is current at the front where the voltage varies from 0 to 10 volts.  See the Catt Anomaly diagram.  The lie in the Catt Anomaly diagram is that displacement current flows from one conductor to the other in all places, allowing electric current behind the front.  Theory C holds true behind the front of a logic step, as well as in the steady, charged capacitor.  Unless, that is, the magnetic field from the opposite conductor causes the current in the conductor of interest, which is of course what happens.  Each conductor causes the current in the other one.  At the front it is due to electromagnetic radiation emission due to charge accelerated by the electric voltage varying from 0 to 10 volts, and where the voltage is steady at 10 volts, the electric current is caused by the magnetic field from the other conductor.  In each case the electromagnetic radiation emission and the magnetic field from each conductor causes the current in the other conductor, a mutual induction situation.  At a large distance from the transmission line, no electromagnetic radiation or magnetic field exists, because the contribution from each conductor cancels that from the other conductor exactly in perfect interference.  So there is no energy lost from the system by radiation, 100% is exchanged between the two conductors, causing the currents in each of them.  Nigel 172.213.66.114 14:56, 9 March 2006 (UTC)

message: Just come across another problem quoted by Nigel Cook. When a capacitor is in series with a load, how exactly does the energy get from one plate to the other. Does this need displacement current?. If so, how is this displaement current generated? --Light current 20:37, 19 December 2005 (UTC)
replies: text: The energy is transmitted when the field goes across the places.  And, the energy goes through the wires on either side of the plate.  Pfalstad 20:43, 19 December 2005 (UTC)

text: Right you are!  Interesting.  Well, then the energy goes down the wires.  It doesn't go across the plate.  Pfalstad 20:58, 19 December 2005 (UTC)

text: No, I meant it stops at the capacitors as if they were an open circuit.  Pfalstad 21:53, 19 December 2005 (UTC)

text: Interesting! Im going to think about that for a while. Needless to say, I dont know the answer.--Light current 22:30, 19 December 2005 (UTC)

text: Do you mean arrange cct as below: ?
       
        ----------------------------|                              
                                    |___
                                    ____  C (Zo is very low)
                                    |
                    Energy flow   |--|
                     ----->       |  |
                                  |  | R Load
          ac source(Zout=R)       |  |
                                  |--|
                                    |___
                                    ____  C (Zo is very low)
                                    |
        ----------------------------|
yes.
I've drawn the Cs as little transmission lines to help us in thinking about this cct. This arrangement of components would indicate that the energy gets shared between the 3 components initially but we know that the Cs do not charge up and can therefore hold no energy. If they do not hold energy, they must reflect it. 
Ah ha! Maybe the energy stolen by the capacitors in the first few ns (2 way transit time of TL) is given back to the load or source after reflection. Probably given back to the source actually (assuming matched source and load resistances). (ie the capacitors introduce a small but positive mismatch to the source)
Any reaction to my thoughts?--Light current 23:07, 19 December 2005 (UTC)

text: Well the capacitors definitely charge, and they hold energy when charged. I'm not sure I understand what you are saying.  Pfalstad 23:16, 19 December 2005 (UTC)

text: There you go again, assuming the high-frequency limit without saying it.  Ok, in that case the caps charge very little.  I don't think I understand enough about your cap-as-TL model to say whether the energy is reflected or what happens to it.  Pfalstad 23:52, 19 December 2005 (UTC)

text: I don't think anyone disputes that the transmission of energy across the capacitor all happens by EM fields.  I certainly don't.  I don't understand how the TL representation helps.  Of course I mentally picture a TL as a chain of caps and inductors.  I suppose you have lots of experience with TL's, so perhaps they are more comfortable for you to work with. User:Pfalstad
Now in one limit, if we make the capacitors smaller and smaller the energy transferred to the resistor will tend to zero. In this case all the energy must be reflected back to the source by the capacitors. In the other limit, where C-->oo, none on the energy is reflected back to source. So the only effect the capacitors have is to decide how much of the incident radiation is reflected! Current does NOT need to pass from one plate to another. Energy enters the resistor sideways. Energy enters the capacitors sideways and is reflected (to a greater or lesser degree). (See : Talk:displacement current to see what Nigel said).--Light current 00:19, 20 December 2005 (UTC)
thread_title:  An earlier exchange of thoughts- 

message: Nigel, you have definitely got a problem with your differentials! Firstly, let me point out that you are not dealing with the motion of the electrons, but the motion of the electrons after the random motion due to the thermal energy has been "averaged out". Secondly, if we are working within Catt's calculations, there is no electrical resistance. because Catt uses the version of the Telegrapher's Equations that assume that the resistance is zero!Kevin
:Kevin, since you are interrupting so will I.  We have discussed the fact that the conduction electrons are going at 1 % of the speed of light due to normal motions, and that the 1 mm/s drift is a net drift.  The random drifts don't affect my argument, and I don't need to mention all the details repeatedly for this reason.  As you say resistance is important and added to the characteristic impedance, it determines the current.  But I still want to know what is going on regards "displacement current", i.e., the mechanism of the transverse action in the medium between the conductors.  It is not all longitudinal push.  Nigel 172.213.66.114 19:08, 9 March 2006 (UTC)
replies: text: Gentlemen! please try to the follow the simple rules I outlined at the beginning and dont interrupt each others posts. I know its very tempting to do so- but you must resist that temptation!.Also try to keep your posts short and to the point without bringing in too many different threads in one post. THanks--Light current 23:22, 9 March 2006 (UTC)

text: Kevin please try to only post one msg at a time. It will be easier for everyone. Thanks--Light current 02:56, 10 March 2006 (UTC)
thread_title:  Kevin to Nigel