RC Circuit: How Does Current Flow?

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SUMMARY

The discussion focuses on the behavior of current flow in a simple RC circuit consisting of a battery, resistor, and capacitor. When the capacitor charges, electrons accumulate on one plate, creating a potential difference that allows current to flow through the circuit. The flow of current continues until the potential difference across the capacitor equals the battery's voltage, at which point the electric field in the wire dissipates, halting the current flow. This process is governed by the relationship defined by the equation q = CV, where q is the charge, C is the capacitance, and V is the voltage.

PREREQUISITES
  • Understanding of basic electrical concepts, including voltage, current, and resistance.
  • Familiarity with RC circuit components: resistors, capacitors, and EMF batteries.
  • Knowledge of the relationship between charge, capacitance, and voltage (q = CV).
  • Basic principles of electric fields and potential difference.
NEXT STEPS
  • Study the charging and discharging cycles of capacitors in RC circuits.
  • Learn about the time constant in RC circuits and its impact on current flow.
  • Explore the effects of varying resistance and capacitance on circuit behavior.
  • Investigate the role of electric fields in circuit dynamics and charge movement.
USEFUL FOR

Students studying electrical engineering, educators teaching circuit theory, and hobbyists interested in electronics and circuit design.

ajcoelho
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Homework Statement



My question is very simple and perhaps it has an obvious answer.

So, if we have a simple RC circuit with and EMF battery, a resistance and a capacitor, when the capacitor is charging, electrons leave the negative terminal of the battery and accumulate on one of the capacitor plates. This way, how is there a current on the other side of the circuit? If electrons accumulate in one side of the capacitor, they will not "complete" the circuit, right?

On the other hand, when the capacitor is full charged, how does the EMF "knows it" and stop "sending" electrons out? :-p
 
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Initially, when the plates are uncharged, the potential difference between them is zero. As the plates become oppositely charged, the potential difference between the plates increases until it equals the potential difference between the terminals of the battery.

At that point, the positive plate and the positive terminal of the battery are at the same potential and there is no electric field in the wire between them.

Similarly, the negative plate and the negative terminal reach the same potential and there is no electric field in the wire between them.

With no electric field in the wire, there is nothing to do work on the charge carriers to drive them. Hence the flow stops and the capacitor is then fully charged with ##q = CV##.
 
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ajcoelho said:

Homework Statement



My question is very simple and perhaps it has an obvious answer.

So, if we have a simple RC circuit with and EMF battery, a resistance and a capacitor, when the capacitor is charging, electrons leave the negative terminal of the battery and accumulate on one of the capacitor plates. This way, how is there a current on the other side of the circuit? If electrons accumulate in one side of the capacitor, they will not "complete" the circuit, right?

The negative charge accumulated on one plate of the capacitor repulses the free electrons of the other plate so they flow towards the positive terminal of the battery.

ehild
 
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