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Have a strange question

  1. Aug 30, 2009 #1
    Okay, if we have a parallel plate and we force a negative charge to the negative plate and a positive charge to the positive plate (both having the same charge) and release them both at the same time, how do we calculate the current?
  2. jcsd
  3. Aug 31, 2009 #2
    More information is needed namely the capacitance of your arrangement,the magnitude of the charge and the resistance of the circuit.
    Last edited: Aug 31, 2009
  4. Aug 31, 2009 #3
    i'm not actually looking for a value, just wondering how in such a system current would be determined
  5. Aug 31, 2009 #4
    Hello IPwnNUBS.
    Show what you already know and report back.
  6. Aug 31, 2009 #5
    Are you talking about capacitors here?
    When we say that one plate is negatively charged and the other is positively charged, it actually means that the negative plate has an excess of electrons which comes from the positive plate,
    so positive can also mean a deficit of negative charge.
    There is nothing such as a positive charge in electric circuits...though we use the word positive charge because the flow of positive charges was found to be equivalent to the flow of electrons in opposite direction (also known as conventional current).
  7. Aug 31, 2009 #6
    True.Treating the OPs arrangement as a capacitor is an easy way to answer his question but it may be homework and he needs to show what he already knows.
  8. Aug 31, 2009 #7
    I actually have a question on this. A positive charge going right would have the same effect as a negative charge going left. But would both currents be equal? Or would one current be positive and the other be negative. Also, is current a scalar or vector quantity? Thanks
  9. Aug 31, 2009 #8
    The scientists in the past didn't know that electrons create current, so they imagined that current is due to a flow of positive charges (which are actually protons/nuclei which don't move at all). But after discovering electrons to be the current creators, they thought:" hey what the hell, why do we have to change the direction of the arrows?? The effects of the current are still the same!!" So the positive charges do not move at all.. If you increase the negative charge in a substance, you can think of it as decreasing the positive charge, the removal of electrons is causing a positive charge.
  10. Aug 31, 2009 #9
    Okay so if we have 1C of negative charge flowing per second, is the current -1C/s or just 1C/s. I've never really understood whether to include the negative charge or not on currents.
  11. Aug 31, 2009 #10
    No it's gonna be positive...because after understanding that electrons flow, we're gonna have to use the conventional current...i.e. Flow of positive charges.
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