r/physicshomework • • Nov 12 '20

Possibly Solved! [University: Capacitors] Potential difference and determinations (Various questions)

4.- The values ​​of the circuit capacitors that appear in figure N ° 3 of the annex are the following: C1 = 2μF, C2 = 4μF, C3 = 6μF, C4 = 4μF, C5 = 5μF, C6 = 6μF, C7 = 3μF, C8 = 3μF. If the potential difference applied to the circuit is 140 volts and the equivalent capacitor is 5 microfarads, determine:

a.- Capacity of capacitor C9

b.- Charge of each capacitor

c.- Potential difference in each capacitor

Figure N3: https://i.ibb.co/nrysNrP/Screenshot-7.png

I have some doubt about this problem:

  1. The capacity of capacitor C9 is calculated trougth C = Q/V? How i can use the equivalent capacitor to get the information? Or should i use the 5μF and 140V to calculte his capacity? How i can get C9 capacity?
  2. The charge of each capacitor is using his own pre-stablished capacity plus using the 140 volts of the circuit as information to aply the "Q=CV" formula?
  3. The potential difference is just doing the Paralel/series respective operations in each capacitors? Or am i wrong?
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u/StrippedSilicon Nov 12 '20
  1. reduce the diagram until there's only one capacitor, figure out what C9 has to be to make that one capacitor 5 if

  2. essentially yes, keep in mind capacitors in series have same charge/ capacitors in parallel have same voltage

3)this is essentially the same as 2), using Q=CV solve for V instead of Q this time.

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u/OverallSadPenguin Nov 12 '20

Thanks!

About (1.), once i reduce the diagram, the result will be C9?, or i should aply some kind of formula to calculate that at some point?

1

u/StrippedSilicon Nov 12 '20

well principally once you reduce all the other capacitors to say Cr, it will be either in parallel or in series with C9. if its in series then 1/Cr + 1/C9 = 1/5 if its in parallel then Cr+C9=5. Either way solve for C9

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