Understanding Negative Current in Discharging Capacitors

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In summary, the conversation discusses the concept of negative current and its two meanings: the rate of change of charge is negative and the current is flowing in the opposite direction. It also verifies the correctness of a given equation and clarifies that in this case, the current direction shown in the diagram is correct.
  • #1
Pushoam
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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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  • #2
Pushoam said:
Is this correct so far?
Yes.
 
  • #3
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.
 

Related to Understanding Negative Current in Discharging Capacitors

What is discharging of a capacitor?

Discharging of a capacitor is the process of releasing the stored electrical energy in the capacitor. This results in a decrease in voltage across the capacitor and a flow of current through the circuit.

How does discharging of a capacitor occur?

When a capacitor is connected to a circuit, it accumulates electrical charge on its plates. This creates a potential difference between the plates, causing the capacitor to store energy. When the circuit is opened or a resistor is connected, the capacitor begins to discharge, releasing the stored energy.

What factors affect the rate of discharging?

The rate of discharging is affected by the capacitance of the capacitor, the resistance of the circuit, and the initial voltage across the capacitor. A larger capacitance will result in a slower discharge, while a higher resistance will cause a faster discharge. The initial voltage also affects the rate, with a higher initial voltage resulting in a faster discharge.

Is discharging of a capacitor a reversible process?

No, discharging of a capacitor is not a reversible process. Once the stored energy is released, the capacitor cannot recover it. To regain its original charge, the capacitor must be connected to a power source and charged again.

What are some practical applications of discharging of a capacitor?

Discharging of a capacitor has many practical applications, such as in camera flashes, defibrillators, and flashlights. Capacitors can also be used to filter and stabilize electrical signals in electronic devices.

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