Understanding Negative Current in Discharging Capacitors

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The discussion focuses on understanding negative current in discharging capacitors, emphasizing that as time progresses, the potential difference across the capacitor and resistor decreases, leading to a reduction in current. It clarifies that negative current can indicate either a decrease in the number of charged particles or a flow in the opposite direction. However, in this context, negative current signifies a reduction in current over time rather than a reversal of direction. The equations presented confirm the relationship between voltage, charge, and current. Overall, the concept of negative current is accurately interpreted as a decrease in charge flow rather than a change in current direction.
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Homework Statement


upload_2017-9-1_11-24-38.png


Homework Equations

The Attempt at a Solution


A)Clearly,
##V_A - V_B >0
\\V_C - V_D >0## as the current flows from higher potential to the lower potential.
As the time passes on, the potential difference across the capacitor as well as the resistor goes on decreasing. Consequently, according to Ohm's law, the current goes on decreasing. This means that either the speed of the charged particles is decreasing or the no. of charged particles passing through the resistor is decreasing.
Assuming that it is the no. of charged particles which is decreasing, keeping the speed constant,
the current defined ,here , as I = ## \frac {dq}{dt} ## is negative.

So, the concept "negative current" has two meanings : 1) ## \frac {dq}{dt} ## is negative.
2) the current is flowing in the opposite direction. Right?

Now,
##[V_A - V_B= q/C ] = [ V_C - V_D = - \frac {dq}{dt} R##
Is this correct so far?
 

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Pushoam said:
Is this correct so far?
Yes.
 
Pushoam said:
) dqdtdqdt \frac {dq}{dt} is negative.
This is correct.
Pushoam said:
the current is flowing in the opposite direction. Right?
No. In this case, the direction shown in the diagram is correct. So negative dq/dt means current reduces over time.
 
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