charge & flow debate

Discussion in 'General Electronics Chat' started by Ratch, Jul 15, 2008.

  1. Ratch

    Thread Starter New Member

    Mar 20, 2007
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    redshaw,

    Yes, that is the first thing to do when analyzing series circuits. By the way, current does not flow, it exists. It is charge that flows. First find the impedance. Begin by calculating the reactance of the inductor. Then add the resistance and the reactance vectorially to get the impedance. You know that reactance is 90 degrees out of phase with the resistance, don't you? Then use the impedance formula and divide the impedance into the voltage to get the current. Multiplying the current by the resistance gives the voltage across the resistor. Ditto for the inductance. I^2*R gives the power dissipated by the resistor. No power is dissipated by the inductance. I did not give you a detailed solution because you should know how to do the steps and have a idea of how things relate to each other. Ratch
     
  2. theamber

    Active Member

    Jun 13, 2008
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    Actually charge does not really flows either is there to begin with.
    The atoms of the material that closes the circuit have charge already, the EMF stimulated those atoms them those atoms stimulate the one next to them and so successively nothing flows like in a water channel which has no water in front. To the contrary the electrons do not move more than within the next atom some will be more lazy to move like in a resistance path for example and will require higher EMF to be estimulated. In an electrical circuit the next electron that happens to be closer to the next atom will get into its next atom and so on. In reality the transmission medium is just a mesh of intrisic particles for conduction. They just invade the next atom and the next atom releases the extra electron to the next one.
    Also you paraphrased it wrong Inductive reactance causes current to lagg the voltage and causes their waveforms (I/V) to be out of phase.The inductor trys to hold the current for a period of time it does not like changes in current. An inductor does have a small resistance called resistivity plus skin effect losses.
     
  3. thingmaker3

    Retired Moderator

    May 16, 2005
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    Debates do not belong in the Homework Forum.
     
  4. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
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    May I quote myself on what I said on the other debate (BJT's don't work like that), since you still insist on picking an argument to support Beaty's "ideas"?
    So, this only adds up with theamber's argument. However, I do agree that there are no flows of current. The same applies to flows of charge, and that's where we disagree, I'm afraid.

    Electrons don't move continuously, either. They "jump" from atom to atom, freeing other electrons while going to a lower energy state. Some of them (almost about half, indeed) will even "jump" back, against the net flowing direction.

    Indeed. This should be moved to the Debates section. :D
     
    Last edited: Jul 16, 2008
  5. Ratch

    Thread Starter New Member

    Mar 20, 2007
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    theamber,

    I was talking about charge in the context of current. Of course everyone knows that charge does not have to move, as in a open circuit. But when it does, it is called current. Also everyone should know that good conductors contain a abundance of charge carriers. And the charge carrier that goes into a circuit is not the same carrier that immediately comes out. Like marbles in a hose. What did I say that was wrong?

    What and where did I paraphrase something wrong? Everyone knows that current lags voltage in an inductive circuit. The inductor effectively robs the charge carriers of their energy while it builds a magnetic field. This loss of energy slows the charge carriers and reduces the current during the field buildup. It releases the energy during the second part of the cycle so the charge carriers move faster thereby increasing the current. We also know that inductors have a finite resistance which is usually treated separately. Have I said differently somewhere? Ratch
     
  6. Ratch

    Thread Starter New Member

    Mar 20, 2007
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    cumesoftware,

    Of course charge carriers and therefore charge can move along a wire. They have to in order to make a electrical circuit. The charge carriers, which are electrons in metals, move along like marbles in a hose when a voltage is applied. The actual movement of electrons, called the drift velocity, is actually very low But when one electron goes into a wire, another different electron comes out the other end at the within the time of the speed of light. There is no charge buildup because electrons are removed from one end of the wire as soon as they are inserted at the other end.

    Electrons do move continuously, but not always in the direction desired. If the current depended on the drift velocity of the electrons, it would take several seconds for a signal to get from one end of the wire to the other, even if the length was only a few inches. Ratch
     
  7. theamber

    Active Member

    Jun 13, 2008
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    Mr. Ratch
    Verbatim you said: "It is charge that flows"
    Verbatim you said: "You know that reactance is 90 degrees out of phase with the resistance, don't you?"
    Verbatim you said: "No power is dissipated by the inductance"
    First it is clear now that flowing as it is defined is not what actually happens. This is according to the Rutherford scattering experiment (which can be wrong) but unless someone comes with another experiment to prove the contrary I stick with it.
    Second how can you see a waveform of reactance or resistance? (they don't behave like waveforms they are resistive quantities that manipulate the waveforms of I/V). I guess for the OP to better understand I would of say that reactance caused the V and I waveforms to be out of phase when they are passing thorugh the resistive elements. I just never saw or heard anyone saying reactance is 90 degrees out of phase with resistance, but I do heard a lot people saying that a current waveform is out of phase with a voltage waveform.
    Third Inductors do consume power in the real world. I just added that as a mere note so that the OP don't get the wrong ideas.
    I want to make something clear I am not personally attacking you nor implying that you do not know that. I was just adding a clarification note in order to create less confussion for the OP. No hard feelings, we are cool on that.
     
  8. Ratch

    Thread Starter New Member

    Mar 20, 2007
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    theamber,

    Yes, in the context of current, charge really does flow past a point in a circuit. Is that wrong?

    Yes, the impedance caused by reactance is 90 degrees out of phase with resistance. Is that wrong?

    Yes, pure impedance does not dissipate any energy and therefore power. Is that wrong? Usually the relatively small resistance of the inductor is considered as a separate resistance. Is that wrong?

    It is not clear to me what you mean by flowing as it is defined. And how does the Rutherford scattering experiment tie into it. Remember, we are talking about charge flow in a wire.

    You cannot see reactance or resistance, only its effects. Have you ever heard of the impedance triangle, where reactance is drawn 90 degrees out of phase with the resistance?

    Sure they do, but the reactance of the inductors does not. If a inductor has a significant amount of resistance, that is taken into account by drawing and calculating its resistance in series with the inductor. Ratch
     
  9. theamber

    Active Member

    Jun 13, 2008
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    Mr. Ratch, I respect your opinion but I do not share your view.
    I rest my case.
     
  10. cumesoftware

    Senior Member

    Apr 27, 2007
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    It is quite evident that you are into "scientific debates". I would like to see an electron moving continuously, but the fact that they don't is quite evident when you see a conductor heating when biased by a current. This is called friction.

    Electrons only move continuously when in vacuum.

    Well, I've presented hard evidence once more, and I won't do it again. These debates are a flop, judging by the number of members that reply.
     
  11. Ratch

    Thread Starter New Member

    Mar 20, 2007
    1,068
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    comesoftware,

    Yes, I do like scientific debates.

    Resistive heating is not a mechanical phenomena, so it is not a frictional mechanism. At the microscopic level, it is a quantum physics event involving speed distribution of conduction electrons, number of collisions with the ionic cores of the material, the average distance a electron travels before colliding with something, changes in the drift speed of the electrons, and a whole lot more. Moving the charge carriers (electrons in this case) in one direction cause more electron collisions to occur with the material lattice than would happen if no movement were present. This causes the electrons to lose some of their kinetic energy, which is transferred to the ionic core of the material lattice by the collisions. This makes the lattice vibrate faster, which by quantum theory, raises the temperature of the resistive material. If the voltage remains constant, the loss of electron kinetic energy causes a slower electron drift velocity, which in turn means less charge entering and leaving the resistor per unit time, so the current will be less. The charge flow response is almost instantaneous, and the charge flow per unit time (current) is decreased. That is why resistance decreases current and dissipates heat when current is present.

    To summarize. Some of the electrons collide with the material lattice and transfer a part of their kinetic energy to the lattice, causing the resistance material to increase in temperature. The loss of kinetic energy of the electrons causes their drift velocity to decrease, thereby also decreasing the current.

    Electrons are always on the move. They move in a continuous direction when traveling in a vacuum.

    What hard evidence?

    Your choice, your judgement. Ratch
     
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