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Direction of current

  1. Jan 31, 2017 #1
    If current flows from + to - for example, which pole has greater potential? I assume the + pole has greater potential, but my teacher says otherwise.
     
  2. jcsd
  3. Jan 31, 2017 #2
    Neither has "greater potential" per se. They have a potential in relation to each other within your circuit. There is a greater concentration of electrons on the negative terminal of a battery; the voltage i.e. potential difference in relation to the positive will drive the current to the other pole. From this perspective the negative terminal will have a higher potential, but it is important to always clearly define your voltage as being between two points. If you put a multimeter's positive lead to a 9V battery's anode and the negative to the cathode, you'll get a reading of 9 Vdc. Flip them on the same battery and you'll get -9 Vdc.

    BTW current flow can be defined as either conventional flow or electron flow. Conventional flow is positive to negative, electron flow is negative to positive. It's the same physical flow regardless of what label you put on it. It's just important to note which you're describing to provide proper frame of reference.
     
    Last edited: Jan 31, 2017
  4. Jan 31, 2017 #3
    This is the concrete problem:

    Inward directed magnetic field passes through surface area of 0.01 m^2 as shown in the image below and changes from 4 T to -4 T in 4 seconds. What is the voltage measured on a voltmeter? (note: voltmeter measures positive voltage when the potential is higher on the positive pole)
    Screenshot_2017_01_31_17_28_29_2.jpg
     
  5. Jan 31, 2017 #4

    jim hardy

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  6. Jan 31, 2017 #5
    The article mainly discusses the direction and magnitude of current which I can determine easily. But I don't understand how can we predict the measured voltage if we only know the direction and value of current. (voltage is positive when there is more potential near the positive pole so what I really want to know is near what pole will potential be greater)
     
  7. Jan 31, 2017 #6

    jim hardy

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    What is your understanding of the definition for "potential " ?
     
  8. Feb 27, 2017 #7
    There are two ways for representing the direction of current, when you see a circuit diagram it's possible to see one of the both, sometimes you can see the classical representation and sometimes the real representation of the current flow.
    Physically the electrons move from the negative pole to the positive pole.
    Also more information, https://www.infootec.net/en/electron-current-conventional-electric-current/
     
  9. Feb 27, 2017 #8
    Some good clear answers in here, helpful thanks, I always over complicate relatively simple concepts when explaining to others in my job!
     
  10. Feb 27, 2017 #9

    Averagesupernova

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    Depending upon how deep one delves into what is happening in circuits, conductors, semiconductors, etc. it may or may not be relevant which way current flows. Electricians who wire our houses, factories, etc. just plain don't need to know. Folks who design semiconductors certainly need to know a lot more. My advice to someone who cannot see how current can flow from negative to positive is usually to file a complaint with Ben Franklin.
    -
    One place I didn't think it mattered which way current flows but it seems that it does is ignition. An arc occur more easily if the sharp pointy electrode is negative relative to the other electrode. I'm still learning.
     
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