Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Electric Current clarification

  1. May 15, 2010 #1
    Hi, I need some clarification regarding electric current and why charge flows in a conductor when connected to an EMF source.

    I was under the impression the EMF source (battery) produced electrons which were 'ejected' into the conductor, these electrons would then flow around the circuit toward the positive end of the battery.

    Reading some information recently, I was given the impression that: conductors (metals etc) have free moving electrons in their lattice which when a potential difference is applied are stimulated to move toward the positive terminal of the battery, they are then reapplied at the negative end and continue to flow around the circuit according to the conductor's resistance value. The volts of the battery is just a measure of the extent of potential difference between the positive and negative terminals of the battery which dictates the amount of energy each coulomb of charge are given and how rapidly they flow around the circuit.

    Is this so? Clarification will be much appreciated.
  2. jcsd
  3. May 16, 2010 #2
    Can anyone help me? thanks.
  4. May 16, 2010 #3
    I don't understand everything perfectly myself, and was actually looking at information about generators when I stopped in here, but I'll do my best to help you out.

    It seems from your post that you have things pretty much correct. Opposite charges attract each other and same charges repel. This causes there to be electric potential energy when charges are near each other, in the same way there is potential energy when masses are close to each other. A volt is a measure of this energy per charge, or the measure of joules per coulomb.

    Imagine a block that has several forces acting on it, such as gravity and the normal force. Even though there are forces acting on it, there is no acceleration, or velocity because the forces cancel each other. If there is a difference between these forces, then you will get acceleration and velocity. The same can be said about voltage. When you have a potential difference, or a difference in potential energy from one place to another, it can cause work to occur to move charges, because they want to move from a high potential to a low potential. This is similar to the way falling objects are moving from a high potential to a low potential.

    This movement from high potential to low potential acts like a pump that keeps the charges moving around, but only in a closed circuit. Think of water being continually pumped through a closed pipe. I hope that helps some. There is, of course, more to it than that, such as currents, AC and DC, magnetic fields and induced electric fields, but hopefully I was able to clear up something in terms of what voltage is.
  5. May 17, 2010 #4
    Mmm yeah, thanks for the response, your block example certainly helped.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook