Puzzled about direct current and charge (flux)

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Discussion Overview

The discussion revolves around the nature of direct current (DC) and its implications for charge accumulation in a circuit. Participants explore the relationship between current, charge, and flux, questioning how these concepts interact over time in the context of a DC circuit.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant asserts that current is defined as the rate of change of charge, leading to the conclusion that charge should accumulate indefinitely in a direct current scenario.
  • Another participant counters this by stating that current represents the rate at which charge flows past a point, suggesting that charge does not accumulate indefinitely at a single point.
  • A further contribution reiterates the initial concern about charge accumulation, questioning how long a direct current can flow into a single point before reaching a critical potential.
  • A later reply acknowledges a misunderstanding regarding the terminology, clarifying that it is the charge that has passed a point that can accumulate, rather than the charge at a point itself.

Areas of Agreement / Disagreement

Participants express differing views on the implications of direct current for charge accumulation, with no consensus reached on the interpretation of these concepts.

Contextual Notes

There are unresolved assumptions regarding the definitions of charge and flux, as well as the implications of current flow in a circuit. The discussion reflects varying interpretations of mathematical relationships without settling on a definitive understanding.

daviddeakin
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This is a question that has kept me awake, trying to rationalise it:

Current is rate-of-change-of-flux (or charge if you prefer, which is the same thing):
i = dQ/dt
Therefore, flux or charge is the time integral of the current.
Q = ∫i dt

Therefore, if you have a direct current, does this not imply that the flux/charge at a given point in the circuit keeps on growing indefinitely??
 
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daviddeakin said:
Therefore, if you have a direct current, does this not imply that the flux/charge at a given point in the circuit keeps on growing indefinitely??
No. The current in a circuit is the rate at which charge is flowing past a surface (or point).
 
daviddeakin said:
This is a question that has kept me awake, trying to rationalise it:

Current is rate-of-change-of-flux (or charge if you prefer, which is the same thing):
i = dQ/dt
Therefore, flux or charge is the time integral of the current.
Q = ∫i dt

Therefore, if you have a direct current, does this not imply that the flux/charge at a given point in the circuit keeps on growing indefinitely??

And how long could you keep this current flowing into a single point? The potential would pretty soon get so large that you couldn't continue. You are mis-interpreting the Maths.
 
Ah, so my mistake was to say "the charge at a given point", when it should be "the charge that has passed a point", which of course can accumulate indefinitely!
 

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