flow of electrons

Discussion in 'General Electronics Chat' started by sense2k, Jul 30, 2009.

  1. sense2k

    Thread Starter New Member

    Jul 30, 2009
    I am trying to fully understand the material.
    Now, in the explanation of flow of electrons thru a wire, when the wire is cut no flow occurs but when another path of wire is introduced to bypass the broken section, why doesn't the broken section carry electron flow?
    I would assume that if I touched any part of the wire I would experience current?

    I know this may seem like an unworthy Q: but I really want to grasp all the concepts 100%

    so thx
  2. KL7AJ

    Senior Member

    Nov 4, 2008

    There are two very different things going on when we think of the flow of electricity. If you were to somehow flag an individual electron in a piece of wire, you'd find that the actual electron drift is slower than a drugged slug. At one ampere, the electron drift is about a centimeter an hour! Not anything like the "speed of electricity." In a wire, electron flow or drift is the movement of electrons from one atom to the next...a very tedious process. What is more important is the transfer of energy from the adjacent electrons "nudging" each other....a process that happens at just under the speed of light.

    In any case howerver, the energy is initiated by a difference of charge, or EMF...Electromotive force. In your example the piece of wire "going nowhere" experiences no EMF...it is the same potential everywhere, unlike inside the completed loop. There is no REASON for any electron OR energy flow in the dead-ended wire.

    You've probably heard the saying that electricity "takes the path of least resistance." Actually, this is not really true. Electricity takes ALL POSSIBLE paths! If you have two paths, one high resistance, and one low resistance, current will travel through both....just that MORE current will flow through the least resistance path.

    Hope this helps a bit!

  3. John5788

    Active Member

    Apr 2, 2009
    not sure what you mean, but when a wire is cut, the electrons stop flowing in that wire because there is no more voltage to "attract" the electrons from flowing.

    however, when you bring a new wire into the picture, there will be a current if there is a new path to ground.
  4. sense2k

    Thread Starter New Member

    Jul 30, 2009
    thx both for replying
    I am referring to the e-book lesson and its diagram(s)

    A B
    ------------- -------------
    ' '

    Am I to understand that no flow is taking place in the wire section AB?
    How would the flow of electrons know to completely bypass that section?

    thx again
  5. sense2k

    Thread Starter New Member

    Jul 30, 2009
    please look at the e-book's diagram
  6. sense2k

    Thread Starter New Member

    Jul 30, 2009
    Conductors, insulators, and electron flow
  7. studiot

    AAC Fanatic!

    Nov 9, 2007
    I will try to explain for you with the aid of the attached sketches.

    At A we have a single piece of conductor or wire, the whole of which is at the same voltage, either zero or connected to one terminal of a battery.

    The electrons shown as - are drifting equally in both directions so there is zero net current flowing. However it is important to remember that the electrons can still move freely about the conductor. The equality is shown by both arrows being the same size.

    At B we have connected each end of the conductor to different battery terminals. Now there is a difference in voltage between the ends of the conductor, although in any small local area the voltage is pretty much constant.
    This voltage difference or gradient cause the electrons to drift towards the +ve end rather more than towards the negative end, as shown by the difference in arrow sizes. We call the difference the current flowing.
    But there is still drift in both directions. The larger the voltage difference the stronger the electron drift towards the +ve.

    At C We have cut the conductor into two, but maintained the connection of each end to a battery terminal.
    Now each part of the conductor is equivalent to the situation in A above. i.e. equal drift in both directions, as shown by the arrows, with zero net current.

    At D we have introduced a bridging link, with part of the old cut conductor sticking out.
    Here the "sticking out" parts conform to my local definition in B above and the arrows show equal drift in both directions, whilst the main body of electron flow is around the bridge.

    I think this is the answer you seek. Yes the electrons do flow dow the dead end branches, but they flow back the other way equally strongly.

    Hope this helps.