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What is the role of the electric field in a battery?

  1. Aug 31, 2009 #1
    I know that the battery creates an electric field around a conductor connected to it, but does this E-field actually do work on the charge, or do the charges go against the field?

    I am treating current as the flow of electrons from negative to positive.
     
  2. jcsd
  3. Aug 31, 2009 #2
    Electrons go against the electric field lines (note that work that occurs naturally is from higher potential energy to lower potential energy; a negative potential energy denotes bounded systems, while energy is a scalar measure). Also take note that an electric field does flow through a conductor (the field lines are altered by the conductor).
     
  4. Aug 31, 2009 #3
    Thanks for the reply.

    I asked this question because of what this resource said:

    "The battery provides a voltage (V) between its terminals. The electric field set up in a wire connected to the battery terminals causes the current to flow, which occurs when the current has a complete conducting path from one terminal of the batter to the other—called a circuit."

    But look at this picture:

    454px-Electric_dipole_field_lines.svg.png

    If the electric field points in such directions, then how does the field push the charges to the positive terminal?
     
  5. Aug 31, 2009 #4
    Those are field lines in a vacuum. The field lines are altered when you put in other objects; so with a conducting wire-circuit, the field lines are actually running through the wire (part of what makes a good conductor a good conductor). The more general Ohm's Law (better viewed quantum mechanically) takes this into account.
     
  6. Sep 1, 2009 #5
    I see. So I'm guessing that charge does not, in fact, flow in the direction of the electric field. Correct?

    Thanks for the help!
     
  7. Sep 1, 2009 #6
    The charges which are free to move in metallic wires are electrons. A current in a metallic wire is therefore a flow of electrons.

    The lines of an electric field show the direction of such field at any point in space, and therefore the direction of the corresponding force that would act on a free positive charge put in such point.

    Electrons are negative charges. Hence they go to the opposite direction, "against" the direction of the E field in the picture, i.e. they go from "-" to "+" as you would expect from the old "charges of equal sign repel each other".

    You should treat current as the flow of positive charge per time unit:

    I = dQ/dt
     
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