More Electrical Things I Can't Wrap my Mind Around

Discussion in 'Physics' started by turkey3_scratch, Jun 30, 2016.

  1. turkey3_scratch

    Thread Starter New Member

    Apr 15, 2016
    15
    1
    My brain is always full of charge! Pun intended. Okay, so my question here relates to voltage and charge, as my usual questions do.

    1) So, let's take a computer power supply, for instance. You have the 12V, 5V, and 3.3V wires. The value of the current on these wires depends on the load the computer is subjected to. Take a 12V wire for example. How can current increase on this wire, let's say you increase it from 5A to 10A, without voltage increasing proportionally? I mean, the voltage lowers a bit as current increases (like what?). Resistance of the wire would only change a little bit due to the heat. Basically, why is this all contrary to Ohm's law? You have a 12V wire with adjustable current, yet voltage and resistance don't change very much and it all does not behave Ohmically. I can't wrap my head around it.
    2) So electric fields connect and attract oppositely-charged particles. But do they also repel like-charged particles? How on earth would you draw that visually? You have the flux lines for protons and electrons being connected, but what would the flux lines look like for repelling charges?
    3) Imagine nothing exists but a vacuum and two electrons. What is their behavior like? Do they constantly push away from each other, and do they push away at a constant velocity or one that decreases as they get farther away?
    4) In a capacitor, as I read in Beaty's article here ( http://amasci.com/emotor/cap1.html ), I learned that one charge enters one plate and the electric field forces another charge out the other, causing a potential difference between the two plates. So in terms of a power supply unit, how the heck does this filter out ripple from high frequency switching?
    4.1) So if you have one plate filled with electrons and the other plate filled with all protons, wouldn't this actually cause the protons in the actual aluminum separating the plates to all leave their atoms and go toward the proton plate, and all the electrons go to their electron plate?
    5) So if two oppositely charged particles are next to each other, such as in an atom, wouldn't the voltage between them cause them to collide and come into contact? Why the heck don't those electrons end up hitting the nucleus if the atom? Is it for the same reason the moon doesn't hit the earth, inertia?
    6) If I somehow got a backpack full of purely protons, could I suck the electrons away from everything I bring it by?
    7) Is it possible for these questions to be answered in an understandable manner without me reading upon some other subject matter? If so, please point me toward that subject.
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,006
    3,232
    My, your mind certainly is a whirlwind of questions -- :D
    1) Ohms law is always obeyed.
    The output current is determined by the load resistance.
    If the output current increases of a supply with a constant output voltage, then the output load resistance must have dropped.
    Why do you think otherwise?
    2) Yes like charged particles repel each other.
    The flux lines for repelling are the same flux lines for attracting. Whether they repel or attract depends upon the relative polarity.
    3) The two electrons continue to repel each other but the force diminishes with the square of the distance between them.
    4) A capacitor suppress ripple precisely because it can absorb charge as the ripple voltage is going positive and then gives up that charge when the ripple voltage starts dropping, which reduces the ripple voltage.
    The larger the capacitor, the better it reduces the ripple.
    4.1) The positive plate of a capacitor is not filled with protons, it's filled with atoms that have lost an electron and thus have a positive charge due to the protons in their nucleus. The protons and atoms don't move appreciably when this happens.
    And if you provide a current path between the two plates of a capacitor than the electrons will migrate back to the positive side so that all the atoms again have neutral charge.
    5) Due to the Pauli electron exclusion principle, electrons occupy distinct quantum orbital states around the nucleus and no two electrons can enter the same state, so it takes extreme energies to get an electron to penetrate an atom's nucleus, such as with a large atom smasher.
    Why that is so, no one knows, but if it weren't true, atoms and the universe as we know it wouldn't exist.
    Here's more on that, if you are interested.
    6) Your sack of protons would fly apart due to their own repulsion so your theoretical experiment is impossible.
    Cold cathode emission is an example of pulling electrons from atoms into free space by an electric field.
    7) I did my best.
     
    Last edited: Jun 30, 2016
  3. turkey3_scratch

    Thread Starter New Member

    Apr 15, 2016
    15
    1
    Ah, so I was right about #1 all along! On a different forum I brought up the idea of resistance adjusting but someone told me that PCs in general and PC power supplies are mostly non-ohmic resistors? Glad to know that was incorrect. For #3, so the force diminishes, so henceforth the velocity at which they repel also decreases, correct? 4.1 makes sense now. I remember quantum orbitals from chemistry class. I totally missed that point about #6.

    Well, thank you, everything is more clear now except #4 is still confusing. But it's probably not really possible for it to be described in any simpler way, I'll just have to accept that that is how they filter ripple. Well, I guess I'll give a shot at asking some more queries about 4.

    So let's talk about the 12VDC output of a power supply. Let's say without any filtering caps ripple (just theoretically, I have no clue what it'd actually be) is 1000mV. Let's say the voltage regulation is top notch, so in reality it fluctuates from 11.5V to 12.5V. Let's say you add a capacitor to that. Not sure what the capacitance or voltage would be, but that don't matter now. Let's say the ripple is lowered to 100mV. So now it fluctuates from 11.95V - 12.05V. I'm going to try to take this frame by frame. So instantaneous voltage at frame 1 is 12V. It starts rising with sine-like behavior toward 12.05V. When this is happening, is the positive plate losing electrons or are the electrons being balanced out? Then, when it starts going down to 11.95V, same thing: is the positive plate losing electrons and becoming unbalanced, or is it balancing out?

    So clearly a "charged" capacitor does not contain the same amount of charge in each plate during the entire operation of the power supply. For some reason I was envisioning that as long as the computer was on the positive plate would have lost all the electrons it could to the negative plate, and when the PC was turned off, it would slowly discharge that negative plate and send the electrons back to the positive plate. But clearly my mental picture was incorrect.
     
  4. crutschow

    Expert

    Mar 14, 2008
    13,006
    3,232
    A capacitor loses electrons as the plate goes more positive with respect to the other plate and gains electrons as it goes more negative.
    It's similar to charging and discharging a battery except that a battery voltage doesn't normally change much as the charges are entering or leaving.
    The charge on a capacitor is equal to Q = C*V so as the voltage goes up and down so does the charge.
    This flow of charge in and out is what reduces the ripple voltage. Since tt absorbs electrons when the ripple voltage goes low and supplies electrons when the ripple goes high, this tends to smooth out the highs and lows.
     
  5. turkey3_scratch

    Thread Starter New Member

    Apr 15, 2016
    15
    1
    When you say the capacitor "loses electrons" don't you mean the positive plate loses electrons? Because according to this article which I have read http://amasci.com/emotor/cap1.html a charged capacitor has the same amount of charge as an uncharged capacitor, but the distribution of the charge between those two plates changes.
     
  6. crutschow

    Expert

    Mar 14, 2008
    13,006
    3,232
    Yes, I meant the positive plate losses electrons but of course, the negative plate acquires an equal number of electrons so the net charge on the capacitor is zero.
     
  7. Papabravo

    Expert

    Feb 24, 2006
    10,140
    1,790
    The Pauli Exclusion principle for fermions is true because the wave functions for two particles must be anitsymmetric. If it were otherwise then the wave function for two particles in the same state would cancel each other with a zero result. Such behavior among fermions has never been observed.
     
  8. crutschow

    Expert

    Mar 14, 2008
    13,006
    3,232
    But we all know that strange things can happen in the Quantum world when things aren't observed.
    Who knows what they do when the lights are out. :rolleyes:
     
  9. Papabravo

    Expert

    Feb 24, 2006
    10,140
    1,790
    I think they pass notes back and forth like giddy high school girls.
     
    cmartinez and shortbus like this.
  10. turkey3_scratch

    Thread Starter New Member

    Apr 15, 2016
    15
    1
    Toy Story: Quantum.
     
  11. BR-549

    Well-Known Member

    Sep 22, 2013
    1,986
    388
    "Such behavior among fermions has never been observed."

    I think it has. I think the matter/anti-matter reaction is such an observation. The resultant charge is zero, but the energy is not. I think the so called Pauli Exclusion principle is trying to describe a variable structure.

    In full disclosure, it has also been observed and described that my thinking is circular and cock-eyed.

    It all depends on the reference.
     
  12. Papabravo

    Expert

    Feb 24, 2006
    10,140
    1,790
    So hows does the wave function of an electron and a positron change when the location of the two particles are exchanged?
     
  13. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
    1,144
    203
    (1) V is REGULATED within some limits, say 5%. When I gets too far out of hand, the circuit behaves non-linearly depending on the power supply design. Some variations are Constant Voltage with Current limit, or Constant Current or Foldback Current Limiting. The circuit is told not to obey ohms law.

    Multi-output and even single output switching supplies MAY have to be loaded to function properly.
    e.g. You may have to 1 A on the 5V supply for the 5V supply to regulate. The 12 V DC supply could be unregulated, but dependent on the 5V load.
     
Loading...