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is this analogy is correct?

Discussion in 'Electronic Design' started by M.Parker, Jul 7, 2009.

  1. M.Parker

    M.Parker Guest

    This post has nothing to do the with different types
    of batteries, just for circuit analysis I provided the below link
    http://en.wikipedia.org/wiki/Daniell_cell

    => The positive connection of that yellow bulb
    instead of connecting it to the copper electrode
    if I connect it to the earth, the circuit is closed.

    now, would the bulb illuminates or not?
     

  2. no.


    w.
     
  3. M.Parker

    M.Parker Guest

    why ?

    if you connected it to earth, you need some way of getting the
    is it really necessary.?

    why do we need 2 wires to conduct electricity

    http://en.wikipedia.org/wiki/Electric_locomotive
    http://en.wikipedia.org/wiki/Pantograph_(rail)
    I'm afraid that electric locomotives has single wire;
    i.e. singlephase
     
  4. baron

    baron Guest

  5. M.Parker

    M.Parker Guest

    Thanks Tom; you are quick and informative.

    Small thought Experiment:

    A rotating Magnetic field will create a Current in a wire(I said a
    single long wire, not 2 pieces, no confusion here)

    now, using this current in that single wire,
    how to make the bulb illuminates?

    If I connect the one end of the wire to the '+' of the bulb
    and the '-' of the bulb to the earth.

    By default, we are left with the other end of the wire as open.

    There is Current in the wire by the effect of the rotating magnetic
    field, it would pass through the '+' of the bulb and there by to
    Tungsten(or whatever it is) and to '-' side of bulb there by to the
    earth.

    then, why can't the Bulb illuminates?
    ==========

    Procedure (2)

    Instead of 1 single long wire, If I take 2 pieces of wires

    One to the '+' of the bulb,
    other to the '-' of the bulb

    at their both ends, if I joined them now the loop is closed.

    If any rotating magnetic field produces the current in the wire
    the bulb will illuminates.

    but, not in the first case, why?
     
  6. M.Parker

    M.Parker Guest

    My one straight question..,

    (q) why the path should be closed to illuminate the bulb?
     
  7. Martin Brown

    Martin Brown Guest

    One of the more spectacular examples is with fluorescent tubes under
    pylons. Richard Box specialised in impressive dusk displays of this as
    artist in residence at Bristol University Physics dept.

    http://www.interactivearchitecture.org/richard-box.html

    Regards,
    Martin Brown
     
  8. John KD5YI

    John KD5YI Guest


    No, the rotating magnetic field will create an electromotive force or
    potential (measured in volts) on the wire. The amount of current (measured
    in amps) that flows in the wire will be a function of the load placed from
    end-to-end on the wire (completing the circuit).


    (remainder snipped due to invalid thought experiment assumption)

    Thanks. Same to you.

    John
     
  9. M.Parker

    M.Parker Guest

    Given my 2 hands,

    one hand holding the electric wire on the pole and
    the other touching the pole.

    => will I feel the electric shock or not ?

    I touch only one wire, but not '2' as you people said for the
    illuminating of the bulb :-(
     
  10. M.Parker

    M.Parker Guest

    Case(a):

    If we connect the '+' end of the bulb to the one of the wires of the
    electric pole and '-' to the earth, would the bulb illuminates or not?

    Case(b):

    If we touch the one of the wires of the electric pole with right hand
    and the left hand to the Earth, would we feel the electric shock or not?

    Both cases are same, but instead of the bulb, if we replace the it with
    a human he can feel the shock, but the bulb will not illuminates.

    what type of logic is this =-O ?
     
  11. M.Parker

    M.Parker Guest

    I will go with the II one; but, I want to hear more reasons
    as I'm not completely satisfied :-\ with the above one.

    so, at the end the conclusion is

    Current is and will always present in "Closed" circuits. But, not in
    open.
     
  12. greg

    greg Guest

    No, there isn't, at least not a continuous one.

    A current will flow for a short time when the wire first
    starts to move through the field. But electrons will start
    to build up at one end of the circuit, and the resulting
    negative charge will tend to stop further electrons from
    flowing in. Similarly, the other end of the circuit will
    acquire a positive charge due to electrons flowing away
    from it, which will tend to attract the electrons back.
    Soon an equilibrium is reached, and no more current flows.

    If you close the circuit, then electrons can flow all
    the way around without building up in any one place, so
    a continuous current is possible.
     
  13. greg

    greg Guest

    Some current will probably flow, because the earth then
    forms part of a closed circuit. Whether it's enough to
    light the bulb depends on the conductivity of the soil
    and the rating of the bulb.
     
  14. greg

    greg Guest

    That depends on how conductive the pole is. You
    certainly have the potential to feel a shock, because
    one side of the mains supply (called the "neutral")
    is connected to the earth, and so is the pole.

    I strongly recommend that you do NOT try this
    experiment!
     
  15. greg

    greg Guest

    Potentially, yes. If the wire that you touch it to is
    the "live" side of the supply, current will flow,
    because of the neutral side being connected to earth.
    If a current flows in one case, it will also flow in the
    other case, although the amount of current will be
    different, because most light bulbs have a much lower
    resistance than a human body does from one hand to the
    other.

    Whether the current is enough to light the lamp or cause
    the human to feel a shock depends on details such as the
    conductivity of the pole and the soil.
     
  16. greg

    greg Guest

    Not always -- it's possible to have a closed circuit
    with no current flowing in it.

    What you can say is that it's *possible* for a continuous
    DC current to flow in a closed circuit, but not in an
    open circuit.
     
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