Direction of the flow

Discussion in 'General Electronics Chat' started by Voltboy, Jul 22, 2007.

  1. Voltboy

    Thread Starter Active Member

    Jan 10, 2007
    197
    0
    im really strating in electronics.. so plz dont blame me for this question.
    Some tutorial say that the electricity goes form negative (-) to positive (+) and somes say its from positives (+) to negative (-) so how it works?.. and when its a circuit with grounds, ground is the negative right?
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    I have always assumed the convention that current flows from the positive most point to the negative most point in the circuit. That means that the current would then need to flow from the negative terminal to positive terminal internal to the voltage source in the circuit.

    The nice thing about the direction of flow is that the math used to analyze the voltages and currents in a circuit allows you to choose an assumed direction and then the sign of the calculated current then indicates whether the direction you have assumed is correct or not.

    hgmjr
     
  3. Voltboy

    Thread Starter Active Member

    Jan 10, 2007
    197
    0
    so its from negative lead of battery to postive, and when its have a ground its from +V to ground?
     
  4. Distort10n

    Active Member

    Dec 25, 2006
    429
    1
    Different text books will use either conventional current flow (positive to negative) or electron current flow (negative to positive). In reality, the electric charge flows from negative to positive. Positive to negative is a historical hold over. Either direction can be used in circuit analysis as long as you are consistent.
     
  5. Voltboy

    Thread Starter Active Member

    Jan 10, 2007
    197
    0
    and when it have ground??
     
  6. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Ground is nothing more than a convenient reference node in a circuit against which many of your measurements are made. Current can flow into the ground node or in some cases out of the ground node.

    hgmjr
     
  7. recca02

    Senior Member

    Apr 2, 2007
    1,211
    0
    conventional direction of flow of current is from higher potential to lower potential. electron flows from lower potential to higher potential.
    there is no absolute zero potential and hence no absolute -ve or +ve.
    they are -ve or =ve or 0 with respect ot some standard potential.

    conventional direction of current assumes +ve charge flows however in conductors this is not possible since protons are too big hence only electrons flow opposite to direction of current assumed.
     
  8. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
    10
    Some tutorials use the conventional current flow, that is positive to negative, and others use the real current flow, negative to positive. The conventional flow exists because it was thought that electrons were positive, thus moving towards a negative charge. Of course electrons are indeed negative. Nevertheless, most books use the conventional corrent flow (that's what is is, "conventional", because it just follows a convention).
     
  9. techroomt

    Senior Member

    May 19, 2004
    198
    1
    current in a solid (wire, components, etc), is the flow of electrons - flows from negative to positive. all science supports this theory.

    however current can exist in gases and liquids as well, where the nuclei can free to move. so ions, or atoms which have gained or lost electrons, can actually act as current.

    there is also what people call hole current, which is what you might call the void, or absence of an electron. as electrons flow one direction, the hole it leaves flows the other direction.

    a ground, or earth reference point (0 vdc, 0 vac) is often placed at a junction in reference to the power being supplied to a circuit. it can be the negative (cathode), which is most common, of the dc power source or positive (anode).
     
  10. vijaya kumari

    New Member

    Jul 23, 2007
    1
    0
    current goes from (+) to (-),that is we term holes as +ve &electrons as -ve.
    as there is no moment for holes, electrons move from their resting place to holes. and this moment of electrons is termed as electricity.but scientist has taken direction of holes(that is during 1880's,they thought that at one day +ve charge would be discovered)as direction of electricity
    And coming to next question,ground is not always -ve,we can also ground the the +ve terminal of a battery or a source to ground.first learn what it meant by grounding
     
  11. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
    10
    To be more accurate, ground is your reference voltage point. Take the case of a "negative voltage" supply. In that case, groung is considered to be the most positive rail. It is easier if you consider "ground" a convention or an abstraction, since it is a rail like any other (with the exception that sometimes is connected to the earth, a practice that I don't advocate).
     
  12. recca02

    Senior Member

    Apr 2, 2007
    1,211
    0
    from my personal experience abt direction of current it pays to keep the direction of positive charge as direction of current else u land up with huge sign troubles while making derivations of direction of electron travel in a magnetic and electric field ad many other such derivations.
    actually i think it was the other way round , determining direction of current due to mag field/electric field/e- motion.
     
  13. Voltboy

    Thread Starter Active Member

    Jan 10, 2007
    197
    0
    so then.. lets say i want to make a circuit, lets say a battery-resistor-led circuit..
    should the resistor be between postive terminal of battery and LED, or between negative terminal of battery and LED, because if its like conventional flow, its between postive and led, but if its like real flow it is between negative and LED.. so how it is?
     
  14. nanovate

    Distinguished Member

    May 7, 2007
    665
    1
    Either way is fine as long as the LED is oriented correctly-- "arrow" pointing towards the negative battery lead (or in direction of conventional current).
     
  15. recca02

    Senior Member

    Apr 2, 2007
    1,211
    0
    the flow of current depends upon the resistance offered by the circuit.
    ohm's law v=ir
    it does not matters where the resistance is placed as long as it is placed in the circuit.
    the current flow is uniform in series elements of circuit it does not vary from element to element.
     
  16. Voltboy

    Thread Starter Active Member

    Jan 10, 2007
    197
    0
    thanks to everyone.. now i understand electronics a bit more:D
     
  17. GonzoTech

    New Member

    Jul 24, 2007
    2
    0
  18. Voltboy

    Thread Starter Active Member

    Jan 10, 2007
    197
    0
    thanks.. that wiki is great:)
     
Loading...