Disconnected vs Connected parallel plate capacitor

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SUMMARY

The discussion clarifies the differences between disconnected and connected parallel plate capacitors, emphasizing that the potential difference (PD) across a connected capacitor is dictated by the voltage source, while a disconnected capacitor's PD is influenced by its instantaneous charge. The formula C(Q/V) = ke0A/d is central to understanding capacitance, where C represents capacitance, Q is charge, V is voltage, ke0 is the permittivity of free space, A is the area of the plates, and d is the distance between them. The capacitance remains constant regardless of the charge or voltage conditions.

PREREQUISITES
  • Understanding of capacitor fundamentals
  • Familiarity with the formula C(Q/V) = ke0A/d
  • Basic knowledge of electrical circuits and voltage sources
  • Concept of charge and potential difference
NEXT STEPS
  • Study the behavior of capacitors in RC circuits
  • Explore the impact of plate area and distance on capacitance
  • Learn about energy stored in capacitors
  • Investigate circuit diagrams for connected and disconnected capacitors
USEFUL FOR

Students of electrical engineering, physics enthusiasts, and anyone seeking to deepen their understanding of capacitor behavior in electrical circuits.

plindle
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I am having a hard time understanding the whole idea behind and the difference between disconnected vs connected parallel plate capacitor in terms of voltage and charge. How does this relate to the formula C(Q/V)=ke0A/d?
 
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plindle said:
I am having a hard time understanding the whole idea behind and the difference between disconnected vs connected parallel plate capacitor in terms of voltage and charge. How does this relate to the formula C(Q/V)=ke0A/d?
The words alone don't have an unique message. What you (and we) would need is a circuit diagram of the two states you want to discuss.
What is certain is that, when a Capacitor is connected across a Voltage source (battery etc.) the PD across it is determined by the source volts. If the capacitor is being charged via a Resistor, the PD is determined by the (perhaps instantaneous) charge on the capacitor.
The Capacitance is determined by the dimensions of the capacitor (and stays the same) and the Charge will be CV, whatever V happens to be across it.
 
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