Two opposite polarity charged capacitors in series

In summary, the conversation discusses the potential difference and flow of charge in a circuit with two capacitors in parallel. It is noted that the voltage does not change for capacitors in parallel. The conversation also explores the flow of charge and polarities when switches are closed. The conversation concludes with a suggestion to use algebra to better understand the balance of charge in the circuit.
  • #1
Painguy
120
0

Homework Statement



W7KpVbQ.png


Homework Equations


Q=C

The Attempt at a Solution


a) I want to say that since both have the same potentials then it is similar to a parallel circuit where the charges can differ on each capacitor. If i think of point A as an input and point B as an output then the potential difference would have to be 100V, but I am not sure.

b)
since both are at the same potential they will no longer transfer charge.

Q1= 10^(-6) * 100=10^(-4) C

Q2 = 3*10^(-6) * 100 = 3 * 10^(-4) C

Is this right?
 
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  • #2
The equation should be Q=CV but I see that you did that in your calculations.. Looks alright to me though. for a), voltage doesn't chance for capacitors in parallel. Although it does seem counterintuitive, that is the case.
 
  • #3
Painguy said:
a) I want to say that since both have the same potentials then it is similar to a parallel circuit where the charges can differ on each capacitor. If i think of point A as an input and point B as an output then the potential difference would have to be 100V, but I am not sure.
The polarities are opposite. When the switches close, there will be a flow of charge through each until both capacitors have the same potential difference again, but now with the same polarity.
 
  • #4
haruspex said:
The polarities are opposite. When the switches close, there will be a flow of charge through each until both capacitors have the same potential difference again, but now with the same polarity.

How would that happen though? If a negative plate transfers its charge to the positive plate of the other capacitor then it just causes a chain reaction around the loop. I'm having a hard time seeing how everything will balance out.
 
  • #5
Painguy said:
How would that happen though? If a negative plate transfers its charge to the positive plate of the other capacitor then it just causes a chain reaction around the loop. I'm having a hard time seeing how everything will balance out.
Let's just do the algebra and see if it becomes clearer to you.
Let the initial charges be +Q1 and -Q1 on C1, +Q2 and -Q2 on C2. Write equations for those. When the switch is closed, assume a quantity of charge Q flows from the +ve of C1 to the +ve of C2. What charge will flow on the negative side? What equations can you write now?
 

1. How do two opposite polarity charged capacitors behave when connected in series?

When two opposite polarity charged capacitors are connected in series, the total capacitance is equal to the product of the individual capacitances divided by the sum of the individual capacitances. This means that the total capacitance will always be smaller than the individual capacitances.

2. What happens to the voltage across each capacitor in a series connection?

In a series connection, the voltage across each capacitor will be equal. This is because the total voltage supplied by the battery is shared between the two capacitors, and the voltage drop across each capacitor is equal in magnitude but opposite in polarity.

3. Is there a limit to the number of capacitors that can be connected in series?

There is no specific limit to the number of capacitors that can be connected in series. However, as more capacitors are added, the total capacitance decreases and the resulting circuit becomes less efficient. Additionally, the total voltage across the capacitors also increases, which could lead to a potential breakdown of the capacitors.

4. How does the charge distribution change in a series connection of capacitors?

In a series connection, the charge on each capacitor will be equal in magnitude but opposite in polarity. This means that the first capacitor will have a positive charge on one plate and a negative charge on the other, while the second capacitor will have a negative charge on one plate and a positive charge on the other.

5. Can two capacitors with different capacitances be connected in series?

Yes, it is possible to connect two capacitors with different capacitances in series. However, the resulting equivalent capacitance will be smaller than the smallest individual capacitance. This is because the larger capacitor will have a smaller voltage drop across it, resulting in a smaller stored charge.

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