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How to determine resistance

  1. Jan 14, 2016 #1
    I was told that for resistors connected in series (whatever the equivalent resistance be) the current flowing through a circuit will be a constant
    Say i had 'n' number of resistors in series connected to say a battery such that the equivalent resistance was equal to that of an insulator, would i still expect to see current flowing through them
    Say i also had a bulb connected along the long chain of resistors (series obviously) would i expect to see the bulb glowing ?
    if i were to replace my chain of resistors with an insulator ( the one i mentioned ) would there be still some current flowing ?
    if i ripped the atoms of the insulator and say that i got each and every atoms of the insulator in series ( that is to avoid current going in parallel because in atomic atoms don't just form 1d structure but also 3d ) would there be current still flowing through it?
    { Given i don't change potential difference or anything else }
    OR ARE MY QUESTIONS VALID AT ALL ?
     
  2. jcsd
  3. Jan 14, 2016 #2

    mfb

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    A perfect insulator has infinite resistance, and you never reach infinity if you keep adding real numbers. There are no perfect insulators, however, so you always get some current, both with materials called insulators and with arbitrary long chains of resistors.
    Only if the current is large enough.
    Yes with a real insulator, no with a theoretical perfect insulator.
    If you change the molecular structure of an insulator you can get a conductor (e.g. compare diamond and graphite), or an insulator again, so there is no general answer to that question.
     
  4. Jan 16, 2016 #3
    For Q no one, can't vacuum be a perfect insulator ( because i guess that even tesla coils don"t work in vacuum)
    For Q no 3, so whatever is connected to two different terminals, there is some current flowing through it, even air ? ( i mean its a gas! atoms hardly touch each other to make a circuit and yet the tesla coil works in air )
     
  5. Jan 16, 2016 #4

    mfb

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    You still get some current from thermal emission of electrons, and breakthrough if the electric field is too strong. That is not conductivity in the classical sense, but there is a current flow.
    Right. Especially if the air has some water vapor or dust in it, but even clean dry air conducts a tiny bit of current.
     
  6. Jan 16, 2016 #5
    Why does e- travel even in between air ( vacuum ) just to reach the other terminal
     
  7. Jan 16, 2016 #6
    By vacuum, i mean inter molecular spaces
     
  8. Jan 16, 2016 #7

    ZapperZ

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    This is no longer about "resistors in series". This is now about vacuum conductivity and field emission. Is this REALLY what you want to learn in this thread?

    Zz.
     
  9. Jan 16, 2016 #8
    nope
     
  10. Jan 16, 2016 #9

    ZapperZ

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    Then maybe you want to backtrack a bit and figure out if you really want to ask the question in Post #5, because that is the direction you are taking.

    Zz.
     
  11. Jan 18, 2016 #10

    CWatters

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    I wondered if you are confusing "constant" and "the same in each resistor"?

    In a series circuit the current is the same in each resistor eg its constant as you travel along a line of resistors.

    It's does not stay constant if you start changing the value of resistors or the number of resistors.

    Sorry if you know this.
     
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