How does electricity actually work?

Discussion in 'Physics' started by Xartrix, May 22, 2009.

  1. Xartrix

    Thread Starter New Member

    May 7, 2009
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    Hello, (my first post)

    Firstm I'd like to note that I'm not a native English speaker and not *very* familiar with differences in technical terms between English and my mother language, so please forgive me for any mistakes that I may make
    --

    For the record, I have read the e-book concerning this topic (which is great btw!), and still have questions.


    I just can't imagine what happens inside a circuit, when it is closed. How are electrons moving through, why? I tried to form some questions, but then realized it would be more confusing and would serve no purpose (other than making things more chaotic)...

    I won't be satisfied with some undetailed "from-the-book" explanation that introduces tons of abstract terms and even more mystified concepts, what I'm interested in is how electrons behave when they leave battery's electrode (and why they leave it, how they interact with the surrounding enviroment, etc)

    Hope some kind sould will find time and explain this "elementary" phenomena to me :)
     
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Hello there and welcome.

    Your English seems pretty good to me. Not perfect but pretty good.

    I am guessing that you are at the beginning of your studies.

    So I suggest you forget about electrons for now. You need an 'overview' of the subject before looking at the detail.

    Electricity is a form of energy. How familiar with energy are you?

    Circuit theory is all about controlling this energy in useful ways.

    When you learn to drive a car you don't need to know how the engine works, just how the controls work.
    Once you know this you may wish to learn more.
     
  3. Xartrix

    Thread Starter New Member

    May 7, 2009
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    I had electricity in high school and while I unerstood it well (as far as calculations are are concerned), but didn't really know where did most of the relationships come from, I was just presented with them as though they were absolute truths

    Energy. One of the abstract concept I was talking about. While I understand it in terms of calculations, I can't really grasp the concept in "real life".

    I'd rather talk about "low-level stuff" (like in computing) then abstract forms, going low-level has helped me understand many things, not related to one another...


    step by step:
    How does battery work (simplified)? Up until now, I imagined it works on the same principle as static electricity (surplus and deficit of charge), am I right?
    [the reason I'm verifying this is because I based *some* assumptions on this fact]
     
  4. beenthere

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  5. bertus

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  6. davebee

    Well-Known Member

    Oct 22, 2008
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    Here's a link that goes right to the point - batteries consist of a chemical reaction where an oxidation (loss of electrons) part has been separated from a reduction (gain of electrons) part, which results in an electrically unbalanced system.

    Add some conductors so wires can be connected to allow the unbalanced charges to flow through an external circuit, and the result is a battery.

    http://www.science.uwaterloo.ca/~cchieh/cact/c123/battery.html
     
  7. Xartrix

    Thread Starter New Member

    May 7, 2009
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    So, I've reviewed what you've all posted, but I felt like it didn't answer my question, so I did my own research (I wonder why I didn't do that in the first place -- maybe because I thought someone will post their view of the issue) and discovered one link that basically answers all of my questions concerning the very basics of electricity:

    http://www.open2.net/science/roughscience/library/batteries.htm
     
  8. voltz

    New Member

    Jun 4, 2009
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    I was reading this thread and started thinking about how exactly is electricity created.

    Volt = 1 joule per coulomb (the amount of energy per charge)
    Amp = Coulomb per second (let her flow like a river)

    I understand the difference between voltage and current but..

    From those two definitions above .. Exactly, as far as electrons are concerned how is the phenomenon of electricity derived. What makes it work together.. Is it just the constant attraction and repulsion that makes it work? Is it the proximity of these charges or electrons that quantify the amount of energy stored in the charge? That is kind of where I am confused the energy contained within each charge how is that put into the charge? I was thinking maybe the closeness of the electrons or is it the closeness of the charge.. Or am I way off..?

    I guess I can understand from just looking at the power lines.. They step voltage up so the line will not fry under a lower voltage. It makes sense that there is more energy per charge at a higher voltage because there are less electrons traversing at a single point on the line as compared to lower voltage (with a load of course).. Or am I way off...

    I am still reading the ebook.. Thanks for providing such a VALUABLE resource.. Not to mention, the forums are great for searching for more knowledge!
     
  9. steinar96

    Active Member

    Apr 18, 2009
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    Volts/Xartrix.. If you really want to know the details of electricity you are gonna have to buy yourself a university physics book which teaches you about electric fields. which will lead you from basic electric fields to relating electric fields to electric potential.

    There you will find equations such as the one which states that the potential required to move a charged particle from A to B is given by.

    V = line integral(from point A to point B) E*dl.

    Here E is a vector field describing the electric field. To grasp the concept of electricity properly you need to learn the physics and the maths behind it.

    Every charged particle emits an electric field. Force (F) acted upon a charged particle (q) by an electric field (E) can be calculated with the formula F = qE. Since every particle creates an electric field any nearby particle experiences a force F = qE depending on the electric field strength at the position of the particle.

    This means that every charged particle interacts with every other charged particle (assuming they have positive or negative charges).

    The potential V is the energy required to move a charged particle some distance C trough the local electric field.

    If you know how to interpret line integrals, and you know how to describe the local electric field, you can calculate how much energy is required or the energy the particle will aquire when moved from A to B.

    We can put it this way:
    Imagine a conducting rod and at time t = 0 we have oposite charge distributions at the ends of the rod. One end is lacking electrons and thus positively charged while the other has plentyfull so that it is negatively charged at that end.

    The positive charge distribution (lack of electrons) creates an electric field which points away from the center of the charge distribution. Inside the rod we can imagine the electric field lines pointing down the rod towards the negative charge distribution.

    The negative charge distribution (too many electrons) creates an electric field of opposite direction relative the the positive distribution, which points towards the center of the charge distribution. With electric field lines also pointing towards the center of the negative charge distribution. (electric field lines always point from positive to negative potential, convention used in calculations)

    If we could see the electric field lines inside the rod we would see an electric field with field lines pointing towards the negative charge distribution.

    The thing is that this unbalanced charge distribution has created an electric field which will perform work on the electrons according to the formula F = qE. This means they will aquire energy and thus momentum once we let time pass in this simulated scenario. Moments later (in a really really short time frame) the electrons will have moved to balance the charge distribution so that the total electric field inside the rod will be zero.

    Charged particles will always attempt to maintain charge balance as long as they are able to move (such as in conducting materials). Because imbalance means nonzero electric field at some points which will perform work on the electrons towards balance.

    The only reason charged particles move is in attempt to create balance.

    As someone mentioned here bellow balance is perhaps not the best or most accurate word (but accurate in a way though) to use but its easier to think of it as that way to begin with or until you've read up on the maths and theory behind the charged particles.
     
    Last edited: Jun 7, 2009
  10. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Not really a good word to use as balance imples (at least) two opposing actions or forces.

    It is perfectly within theory to have a single action in play.
     
  11. loosewire

    AAC Fanatic!

    Apr 25, 2008
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    Xartrix,do you drive a car with a car radio with a 12 volt battery. Do you have
    home c.d. player.Name a Item that you use that you have Interest in how It works.
    like a t.v..I want to try some thing, but you need to help. First you need to reply.
    Anyone else that wants to join in reply. The electric or electronic devise that you want to understand.
    I NEED A VOLUNTEER THAT CAN DRAW WHAT I POST. THANKS
     
  12. b.shahvir

    Active Member

    Jan 6, 2009
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    Ok lets consider i want to understand how a TV set works. Plz explain
    Thanx.
     
  13. steinar96

    Active Member

    Apr 18, 2009
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    The definitions above are SI units. Arbitrary chosen to comply with the SI system if i remember correctly.

    It is the constant attraction and repulsion that makes it work. The nature of this force is not completely known (there might be a particle model for it though) but explaining it comes down to particle physics beyond the scope of electrons and neutrons.

    It is the closeness of the charge that matters according to mathematical equations. If you look at the equation of the electric field around charged particles you'll see that it depends on charge Q and inverse distance r squared. The other stuff makes up a constant.

    <br />
E = \frac{1}{4\pi\varepsilon_0}\frac{Q}{r^2}<br />

    As to answering the exact nature of charges, or why they exist is yet again down to particle physics.

    If i understand you correctly you are asking where the energy in electricity comes from. It might be a bit hard to grasp but the energy comes from manipulating charge distributions. It is not inside the electrons but instead eletric potential bound in the charge distribution. Let's say you have a object that is completely neutral, the positive charge is equal to the negative charge(zero electric field). You need energy to change the charge distribution such that it isnt neutral anymore(nonzero electric field). The energy is returned when the charges go back such that neutrality is restored again.

    If you rub a balloon against your head for a while you can stick it into a wall or a ceiling for a while. You spent energy rubbing the balloon against the top of your head which robbed the balloons some of its electrons making it positively charged. The energy has accumulated in the form of an electric field. When you stick it against the wall the electric field will slowly dissipate as the wall and balloon exchange electrons (electric field applies work to the electrons, giving them momentum). When the balloon is neutral again it will fall to the ground since the eletric field is again zero. And since it's the electric field that applies force to the electrons no forces remain to keep it up agains the ceiling.

    Keep in mind that troughout this we have completely ignore the effect of gravity, since electrons and neutrons have mass they are affected by gravity. In our balloon case the balloon will stick to the wall for as long as the force due to the electric field is stronger then the force of gravity on the balloon.

    The reason they step up the voltage is to minimize line losses due to internal resistance in the wire. Power dissipated is
    <br />
P = \frac{1}{2}VI^2<br />
    If you look at the equation you see the the equation has I(current) squared. Which means that the higher the current the more energy is lost in the wire (converted into heat due to friction). In other words it is much cheaper to step up the voltage to lower the current since V(voltage) isnt squared in the power equation.
     
  14. loosewire

    AAC Fanatic!

    Apr 25, 2008
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    b.shahvir,are you going to draw,lets see sample of your work without
    just putting up a link. Draw me a r/c network. or better yet draw me
    a list of equipment that you work with-a.c. water tower-motor h.p.
    regulated by analog or ditital-type lighting,your v.s.d.'s are very
    complicated also,Includes motors that can cause v.s.d.s your
    utility service could help,and save electric cost. When equipment
    switchs on and off you wide swings in energy that cause v.s.d.'s.
    even If you have shielded cable.this is a complicated subject that
    engineers face every day,because they have to please the public that
    pay to enjoy life without excuse.There is a lot employment for people
    that can understand the equipment.
     
    Last edited: Jun 7, 2009
  15. b.shahvir

    Active Member

    Jan 6, 2009
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    Plz do understand, my intention is not to get into disputes or empty debates. The OP just wants to understand the basic mechanism of electron flow (current) and as such it has nothing to do with the functioning of everyday appliances.
    Cheers!
     
  16. loosewire

    AAC Fanatic!

    Apr 25, 2008
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    You stated that you had problems with v.s.d's just trying to help
    not start bateless debate,I don't complain just ask for your respect
    which you have earned.
     
  17. b.shahvir

    Active Member

    Jan 6, 2009
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    Pardon my ignorance, but I do not understand what you mean by a v.s.d!


    Thanks very much. I'll keep that in mind.


    Best regards,
    Shahvir
     
  18. Xartrix

    Thread Starter New Member

    May 7, 2009
    4
    0
    I just read through the rest of this thread (I thought it died already, but I was pleasently surprised)

    steinar96: excellent job explaining the electric fields, which comfirmed my assumptions

    everyone else: thanks for your input!
     
  19. BillO

    Well-Known Member

    Nov 24, 2008
    985
    136

    Hmm, could be either a hole in the heart or some kind of motor drive, but for some reason I am sure I'm not right.
     
  20. b.shahvir

    Active Member

    Jan 6, 2009
    444
    0

    LW might have mean't a v.f.d. (variable frequency drive) but I ain't sure!
     
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