Conceptual understanding of a capacitor

[texan2414]

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Hi,

I am having a bit of difficulty fully grasping the concept of capacitors as electronic elements.

Consider a simple parallel-plate capacitor:

- My first question is, if there is a resistor added to the circuit element containing the capacitor, how would this affect the capacitance? I postulate that capacitance (ability of capacitor to hold charge) would decrease as the resistor would "suck" charge (current) and dissipate it as heat, thus less charge return on capacitor → inefficient capacitor. Am I correct with my conceptual understanding of this?

- Secondly, I know the "q vs time" graphs for a discharging capacitor is an exponential decay - but how would "voltage vs time" and "current vs time" graphs look like for a discharging capacitor? Would they also depict decay? Why or why not?

I would really really appreciate it if someone could boil this concept down for me. I have missed quite a number of questions where I counterintuitively selected an answer which confused me even more 🙁

Thanks,

 

[Cawolf]

Capacitance is an intrinsic property of the capacitor, it will not be changed by circuit elements. It is simply the ratio of charge to potential (Q/V).

If you increase the resistance of the circuit, the total charge on the capacitor will not change - but the rate at which it charges and discharges will decrease.

For the graphs; charge, potential, and electric field all decay (and increase) exponentially. The relationship between all of these components is linear, so they all change the same - exponentially.

 

[texan2414]

Thanks Cawolf!