Capacitors in series

  • Thread starter Pranav Jha
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  • #1
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Main Question or Discussion Point

----C1------C2------

If the left and right plates of C1 are +ve and -ve charged respectively and the left and right plates of C2 are +ve and -ve charged respectively then why doesn't the current flow from the right plate of C1 to the left plate of C2 when they are connected in series?
 
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Answers and Replies

  • #2
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What do you mean doesn't flow?

The only way for both to become charged is for current to flow. If they are both charged, then current has flowed.
 
  • #3
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I meant won't connecting the two fully charged capacitors together via a connecting wire result in a current to flow from one capacitor to another?
 
  • #4
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So you're talking about shorting the circuit? Or are you leaving each end open as in your picture?
 
  • #5
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will leaving the ends open make any difference? shouldn't a complete path between the negative plate of one capacitor and the positive plate of another capacitor be enough to result in a current flow from the negative plate of the first to the positive plate of the second?
 
  • #6
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If they are fully charged, no current will flow.
 
  • #7
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Once fully charged the combination of right plate of C1 with left plate of C2 and the connecting wire between them becomes an equipotential,that is there is no potential difference between C1 and C2.
Think of say an electron on the right plate of C1.This is repelled by the other electrons on that plate and on the right plate of C2 but attracted to the positive charges on the other two plates,the resultant force being zero.
 
  • #8
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suppose we have a capcitor fully charged that is connected across a p.d of 12 volts. Now, if we add another capacitor in series, the potential of 12V will be divided across the two capacitors. So, the charge is in excess in the first capacitor for the new reduced voltage across it. So, will the current now flow from the first capacitor to the new second capacitor?
 
  • #9
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Once fully charged the combination of right plate of C1 with left plate of C2 and the connecting wire between them becomes an equipotential,that is there is no potential difference between C1 and C2.
Think of say an electron on the right plate of C1.This is repelled by the other electrons on that plate and on the right plate of C2 but attracted to the positive charges on the other two plates,the resultant force being zero.
that does make sense in the terms of electrical forces :D
 
  • #10
----C1------C2------

If the left and right plates of C1 are +ve and -ve charged respectively and the left and right plates of C2 are +ve and -ve charged respectively then why doesn't the current flow from the right plate of C1 to the left plate of C2 when they are connected in series?
Because you are forgetting that there is a voltage drop across each capacitor. Lets say that there is a potential difference of 12 volts across the entire circuit. If you had a voltmeter and put it on the terminals of C1 you would find a drop of 6 volts and you would find the same drop across the terminals of C2, assuming that they are of equal capacitance. The charges do not flow because there is a 6 volt potential opposing them.
 
  • #11
suppose we have a capcitor fully charged that is connected across a p.d of 12 volts. Now, if we add another capacitor in series, the potential of 12V will be divided across the two capacitors. So, the charge is in excess in the first capacitor for the new reduced voltage across it. So, will the current now flow from the first capacitor to the new second capacitor?
If you could break and reform the circuit without discharging the capacitor and they were of equal capacitance half of the charge would flow from one to the other. The total potential across the two would still be 12 volts. Each capacitor would have a drop of 6 volts across it.
 

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