Ions and Electric Field

Discussion in 'General Electronics Chat' started by Mazaag, Jun 1, 2008.

  1. Mazaag

    Thread Starter Senior Member

    Oct 23, 2004
    Hi guys..

    I understand that an electron has electric field lines radiating inwards... do these lines eventually start at a positive charge ? or put another way, do the field lines of a positive charge terminate at a negative charge?

    Do charged ions also have field lines radiating in/outwards ?

    Suppose we have a container which is split into two by a partially permeable membrane, that allows only positive ions (A+) to pass through it. Say we fill one half of the container with a solution that contains both positive cations A+ and negative anions B- .
    Naturally, the A+ ions will diffuse across the membrane to the other side of the container (assuming the ions are in an aqueous solution).

    If the ions also have field lines and contribute to an electric field between A+ and B- , wouldn't there exist an electric field starting at one side of the container ( where the A+ ions diffused into ) and terminating at the B- ions ? and wouldn't this electric field oppose the motion due to diffusion ? And since an increase in diffused A+ ions will cause an increase in the electric field strength opposing the motion, wouldn't that mean that there will be no diffusion at all taking place ?

    Thanks guys..
  2. Caveman

    Senior Member

    Apr 15, 2008
    Not necessarily. The concept of a field describes the situation of a single source in isolation. The electric field is a property of space. It is a vector field. This means that at every point there is a magnitude and direction of the field. Field lines are basically putting the vector arrows end to end for the field to show the path a test charge would travel.

    Now why make it so confusing? Well, other electrons (and protons) can generate other fields in the same space (ie. they overlap). They simply sum up (using vector addition) to a resulting magnitude and strength. Now you can draw the lines that connect each vector arrow end to end to show the resulting path. If another field is added, you just add it to the result.

    So the lines connecting from positive charge to negative is just due to two overlaying fields. One radiates outwards from the postive charge, and the other radiates inwards towards the negative charge. Do you see how this simplifies things?