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Abstract Confusion

  1. Dec 19, 2007 #1
    I just bought the book Art of Electronics that berkman recommended and I just started reading it. I already know what voltage is but if I didn't I would have made no sense of their explanation.

    They say "The voltage between two points is the cost in energy (work done) required to move a unit of positive charge from the more negative point (lower potential) to the more positive point (higher potential).

    Why do they have to give such a complicated explanation for such a simple concept? If I was to explain voltage I'd say "Voltage between two points is the build up of charge (electrons) at one point (negative terminal) which causes current to flow to the other point (electron deficient positive terminal).

    Secondly they say required to move a "positive" unit of charge. Electrons are negative units of charge aren't they? Whats a positive unit of charge?? Protons? A lack of electrons?

    I'm studying a few different scientific fields at the moment and I have to say electronics theory is the most frustrating and complicated.
     
  2. jcsd
  3. Dec 19, 2007 #2
    Is this the Horowitz book? I think it's a great introductory text.

    I think the definition given in the book is quite ok, and with the help of a diagram I would be happy if I was learning voltage concepts with that principle.
    (Voltage as a 'height' or as an analog to gravitation potential)

    I guess we all learn concepts in different ways, so theres no perfect way to teach this stuff.


    With regards to this Positive charge stuff, it's rather unfortunate but "conventional" current was actually defined a long time ago to be the flow of positive charge.
    From my understanding the actual 'charge carrier' can be different things in different materials.. electrons (in solids), ions (ionic solutions), protons (well it's a hydrogen ion)..
     
  4. Dec 19, 2007 #3
    After reading your question, think of voltage as being the difference between a hot pipe and a cold pipe. The hotter the pipe the more chance you will get burned.
     
  5. Dec 19, 2007 #4
    This reply regarding the body of your thread. Think of voltage as being two sides of a football game. One side wants to destroy then other. One side has more electrons than the other side and due to the state police (insulator) they do not fight (short) and thus the potential difference.
     
  6. Dec 19, 2007 #5

    dlgoff

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    The potential difference between two points is found by integrating the electric field over the distance between these two points. See the mathematical definition here.

    Positive current is defined for moving positive charge in the direction of a positive field, so since electrons are negatively charged, the current would be in the oposite direction of the actual electron flow.
     
  7. Dec 19, 2007 #6
    The Art of Electronics is the best introductory book that I've found so far. You made a good choice.

    The concept of voltage is hard to describe in a way that is both accurate and easy to understand. I don't like the definition you present for one reason. You say, "Voltage ... causes current to flow ...." -- that's not quite right. Voltage is a potential, if there is no conductive path it remains only a potential and does not cause current to flow.

    Regarding current direction -- direction is ambiguous because "Ben Franklin Current" is defined as flowing from positive potential to negative potential, however, we know now that electron flow is from the negative potential to positive potential.

    The discrepancy makes sense if you look at the early studies of electricity when they described things in terms they already understood. Electricity was thought to be a fluid, and what we now call voltage was described as high or low pressures of electrical fluid. In terms of fluid, it would obviously 'flow' from high pressure to low pressure.
     
  8. Dec 19, 2007 #7
    I should have said "given a conductive path, causes current to flow to the positive terminal". I didn't really think of it like that asynchro. The fact that the potential difference is there regardless of whether current is flowing. Like in a battery. The potential different exists between both terminals but the electrons can't get to the positive terminal unless you connect a wire from the anode to the cathode.

    I always wondered what stops the electrons from the anode from reaching the cathode by travelling inside the battery rather than outside. Is it just the chemical process or is there an insulator between them inside the cell?

    Yeah I wish they would fix the current concept. Just because its convention doesn't mean its accurate so they should change it. When I was first learning about charge of electrons, protons, anions, cations, anodes and cathodes the conventional idea of current flow added my confusion.
     
    Last edited: Dec 19, 2007
  9. Dec 19, 2007 #8
    There's alot of things we would like to change as with time we find things are different to what we first thought.
    Have a look at the definition for the word 'atom' (greek root) :smile:
     
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