Question about Current and Resistance

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Discussion Overview

The discussion centers on the relationship between current, resistance, and potential difference in electrical circuits. Participants explore whether current can exist without resistance and the implications of such scenarios, including the role of superconductivity and the definitions of current and voltage.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that current can exist in a circuit without a resistor, suggesting that the definition of current does not inherently require resistance.
  • One participant mentions superconductivity as an example of current flowing without energy loss, implying that resistance is not a necessary condition for current.
  • Another participant argues that current is defined as the flow of charge, which can occur even in the absence of resistance, although the rate of flow may be affected by resistance.
  • There is a question raised about the existence of potential difference when current flows without resistance, with some suggesting that inductance or capacitance could still support a voltage.
  • Some participants differentiate between ordinary current and supercurrent, indicating that while ordinary current typically requires a potential difference, supercurrent can exist without one.
  • One participant introduces the concept of a battery being super conductive between terminals, prompting further inquiry into the context of the discussion.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of resistance for current to exist, and whether potential difference can occur without resistance. Multiple competing perspectives remain, and the discussion does not reach a consensus.

Contextual Notes

Participants reference definitions and conditions related to current and voltage, but there are unresolved aspects regarding the implications of superconductivity and the specific conditions under which current and potential difference can coexist.

BuddyGoodness
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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?
 
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there's no loss of electron energy without resistance. eg super conductivity is current w/o loss (no resistance).
 
when electrons move from one place to another there is current. ( or atleast i think that's 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 don't need all three in v=ir... you could have a voltage but do nothing wit it.. and therefore have no current.
 
BuddyGoodness said:
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?

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.
 
ZapperZ said:
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.

Interesting! The natural follow up question is... Suppose then that I have a current with no resistance. Can there be a potential difference?
 
Cantab Morgan said:
Interesting! The natural follow up question is... Suppose then that I have a current with no resistance. Can there be a potential difference?

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 spatial integral of the electric fields, will be zero.
 
Cantab Morgan said:
Interesting! The natural follow up question is... Suppose then that I have a current with no resistance. Can there be a potential difference?

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.
 
Cantab Morgan said:
Interesting! The natural follow up question is... Suppose then that I have a current with no resistance. Can there be a potential difference?

a battery that is super conductive between terminals.

whats the context of the question?
 

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