Why does the potential difference between two capacitors seek equilibrium?

In summary, when two capacitors, C1 and C2, with different initial voltages are connected in parallel, the total charge will remain constant and the voltage will equalize between the two capacitors to reach equilibrium. This is because in electronics, a conductor is simply a container for charge, and the charge will distribute itself evenly between the two capacitors. This can be compared to two water tanks connected by a pipe, where the water will flow until the levels are equal. Similarly, in a wire with different voltages at each end, the charge will flow until the voltages are equal.
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Suppose we have a circuit with two capacitors connected to each other, C1 and C2.

C1 is charged and has a potential difference of 5 V (V1=5V), but C2 is not charged (V2=0)

Apparently it is known that the potential difference of these two capacitors will want to reach equilibrium. So V1=V2.

Why is this? I don't understand why this happens.
 
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Its a bit like having two water tanks connected by a pipe at the bottom.
If they start out at different levels, they are going to want to have the same level.
Why is that?

In electronics, a conductor is just a container for charge, which allows the charge to move freely.
 
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  • #3
Simon Bridge said:
Its a bit like having two water tanks connected by a pipe at the bottom.
If they start out at different levels, they are going to want to have the same level.
Why is that?

In electronics, a conductor is just a container for charge, which allows the charge to move freely.

In the water tank example, I assume it would be because both bodies of water exert a pressure on the water tank pipe. If one tank has more volume than the other, then it exerts more pressure on that side of the pipe (and the pressure from the other tank isn't enough to counteract this force). Then I assume both sides of the pipe's pressure would want to reach equilibrium, so that there will be no more net movement of water.
 
  • #4
Well done... in an uneven level, there would be a higher pressure at one end of the pipe than at the other, so water will flow along it.

Similarly, if the voltage on one end of a wire is higher that at the other end, then what does the charge do?
 
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Well done... in an uneven level, there would be a higher pressure at one end of the pipe than at the other, so water will flow along it.

Similarly, if the voltage on one end of a wire is higher that at the other end, then what does the charge do?
 
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  • #6
Simon Bridge said:
Well done... in an uneven level, there would be a higher pressure at one end of the pipe than at the other, so water will flow along it.

Similarly, if the voltage on one end of a wire is higher that at the other end, then what does the charge do?

The electrons would all go to the higher potential? And this would also probably change the potential, because of all the electrons going there. Then the potential would get lower and disperse along the wire evenly?
 
  • #7
x86 said:
Suppose we have a circuit with two capacitors connected to each other, C1 and C2.
C1 is charged and has a potential difference of 5 V (V1=5V), but C2 is not charged (V2=0)
Apparently it is known that the potential difference of these two capacitors will want to reach equilibrium. So V1=V2.
Why is this? I don't understand why this happens.

...connected to each other ?
I suppose you mean "in parallel" - right?
My answer:
Assuming that C1 is charged with Q1 (equivalent to V1=5V) and is connected at t=0 to another capacitor C2 in parallel, the total charge remains constant (Q1).
As a result we have a new charge distribution between both capacitors - proportional to their capacity C1 resp C2.
Both have, of course, the same voltage (because they share the same nodes) which is V=Q1/C with C=C1+C2.
 
  • #8
Or to put it another way;
Before connection, C1 has a voltage of 5V, while C2 has a voltage of zero.
Capacitance is defined as the ratio of charge to voltage, C = Q / V.
The charge on C1 is Q = C1 * 5V. That is also the total charge available for redistribution.

At the instant of parallel connection, there will be a voltage gradient along the wires used to make the connection. That will allow charge to flow until the voltages reach the same value when the voltage gradient is no longer available to encourage the charge to move.

Two capacitors C1 and C2 when connected in parallel will have a total capacitance of Ct = C1 + C2.
Once connected in parallel the voltage on both capacitors will settle to V = Q / Ct, which is; V = 5V * C1 / Ct.
 

1. Why do capacitors seek equilibrium?

Capacitors seek equilibrium because of the principle of charge conservation. This principle states that charges are not created or destroyed, but they can be redistributed. In the case of capacitors, the potential difference between the two plates causes a redistribution of charges, resulting in an equilibrium state.

2. How does the potential difference between two capacitors affect equilibrium?

The potential difference between two capacitors determines the amount of charge that can be stored on each capacitor. When the potential difference is increased, the amount of charge on each capacitor also increases, until an equilibrium is reached where the potential difference between the two capacitors is equal.

3. Can the potential difference between two capacitors be equal without them seeking equilibrium?

No, the potential difference between two capacitors will always seek equilibrium. This is because of the principle of minimum energy, which states that systems tend to move towards a state of minimum energy. In the case of capacitors, equilibrium is the state of minimum energy.

4. What factors can affect the potential difference between two capacitors?

The potential difference between two capacitors can be affected by the capacitance of the capacitors, the amount of charge on each capacitor, and the distance between the two plates of each capacitor. These factors all contribute to the overall potential difference between the two capacitors.

5. How does the potential difference between two capacitors affect the overall energy stored?

The potential difference between two capacitors is directly proportional to the energy stored in the capacitors. This means that as the potential difference increases, the energy stored also increases. When the potential difference reaches equilibrium, the energy stored is at its maximum and remains constant unless the potential difference is changed again.

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