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Question about Current and Resistance

  1. Apr 8, 2009 #1
    I am curious. Is there any current in a circuit without a resistor? I would think there was but I cannot find anything that answers this question. I don't really see how a resistor is needed to create current (ohms law notwithstanding). Could someone explain this for me?
     
  2. jcsd
  3. Apr 8, 2009 #2
    there's no loss of electron energy without resistance. eg super conductivity is current w/o loss (no resistance).
     
  4. Apr 9, 2009 #3
    when electrons move from one place to another there is current. ( or atleast i think thats how it works, free electrons moving from one place to another) so if you had a bunch of electrons moving through empty space that would be current without resistance. you dont need all three in v=ir... you could have a voltage but do nothing wit it.. and therefore have no current.
     
  5. Apr 9, 2009 #4

    ZapperZ

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    You already have two responses that should answer your question. However, you need to think a bit more on what is meant by "current", i.e. the definition of it. In the simplest term, it is the amount of charge flowing through a unit area per unit time. That's it!

    It says nothing about "resistance" in that definition, even though the presence of resistance can affect the rate of flow. However, without knowing if a resistance is presence or not, the "measurer" of that current only cares about the amount of charge flow and nothing else. That does not depend on the presence of any resistance.

    Zz.
     
  6. Apr 9, 2009 #5
    Interesting! The natural follow up question is.... Suppose then that I have a current with no resistance. Can there be a potential difference?
     
  7. Apr 9, 2009 #6

    Born2bwire

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    Sure, there can still be an inductance or capacitance. The resulting reactance will support a voltage. Classically, if there is no reactance or resistance, then I do not think that there can be any voltage. For example, the boundary conditions on a perfect electrical conductor (zero resistance) require that the tangential electric fields be zero on the surface. That means that the voltage, the spacial integral of the electric fields, will be zero.
     
  8. Apr 9, 2009 #7

    ZapperZ

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    Depends on what TYPE of current. The ordinary current, usually yes, because it is the potential difference that drives the current. For superconductivity/supercurrent, NO. You can have a spontaneous current (example: josephson current) even at no potential bias.

    Zz.
     
  9. Apr 9, 2009 #8
    a battery that is super conductive between terminals.

    whats the context of the question?
     
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