Electricity (Electric potential)

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Discussion Overview

The discussion revolves around understanding the behavior of potential difference across capacitors in different configurations, specifically in parallel and series connections. It includes theoretical explanations and comparisons between capacitors and resistors.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant asks why the potential difference is the same across the gap between the plates of capacitors connected in parallel.
  • Another participant explains that all points connected by a thick copper wire are at the same voltage, leading to equal potential differences across both capacitors in parallel.
  • A question is raised about how the potential difference would change if the capacitors were connected in series.
  • One participant claims that connecting two capacitors in series with a 120V DC supply results in a potential difference of 60V across each, assuming equal capacitance.
  • Another participant adds that the voltage across capacitors in series is shared according to their capacitances, indicating that the voltage is not necessarily equal unless the capacitors have the same value.
  • A comparison is made to resistors in series, where changing resistance values affects the voltage distribution, referred to as a voltage divider.
  • A later reply reiterates that for two capacitors in series, the sum of their individual voltages equals the applied voltage.

Areas of Agreement / Disagreement

Participants express differing views on the behavior of potential difference in series configurations, with some asserting equal voltage distribution under specific conditions while others emphasize the dependence on capacitance values. The discussion remains unresolved regarding the implications of different capacitor values in series.

Contextual Notes

Participants mention conditions under which voltage division occurs, such as equal capacitance in series, but do not fully resolve the implications of varying capacitance values on potential differences.

marvelous
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Hi,can you please help to understand why is the potential difference the same across the gap between the plates of both capacitors connected in parallel?
 
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All points connected together by a thick copper wire are at the same voltage. The "top" terminal of one capacitor is connected by wire to the "top" terminal of the other, causing those terminals to be at the same voltage. The same goes for the "bottom" terminals of both capacitors. So the potential difference across one capacitor is going to be equal to the potential difference across the other.
 
So what if they were connected in series,how would the potential difference be affected?
 
Cut in half , if you connect capacitors in series , say like two capacitors in series , you input say 120v DC you get 60 measuring from the "middle" to the ground.
 
Crazymechanic said:
Cut in half , if you connect capacitors in series , say like two capacitors in series , you input say 120v DC you get 60 measuring from the "middle" to the ground.

That will only be true if the two capacitors have the same value. The initial charge that flows will be equal for the two capacitors so the voltages will be Q/C, in each case. The value of the charge Q will be V(overall series Capacitance). i.e. the voltage is shared according to the inverse of the two capacitances. (Fewer volts across the larger capacitor)
 
Thanks for pointing that out I totally forgot about that , well anyway it's the same as with resistors in series , change the one to a lower resistance and the other one closer to ground to a higher and you get more than half of the original volts you supplied do it the other way around and you get less than half , in both cases capacitor or resistor the thing is called a voltage divider.
 
marvelous said:
So what if they were connected in series,how would the potential difference be affected?
For two capacitors in series, the sum of their individual voltages equals the applied voltage.
 

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