# Puzzled about direct current and charge (flux)

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??

Doc Al
Mentor
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).

sophiecentaur
Gold Member
2020 Award
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!