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Veritasium "How Electricity Actually Works"
electrodacus:
--- Quote from: SandyCox on May 08, 2022, 05:52:01 pm ---When applying circuit theory to the problem, either the law of conservation of charge or the law of conservation of energy is violated.
--- End quote ---
There is no such thing as conservation of charge. The conservation of energy is a law.
SandyCox:
--- Quote from: electrodacus on May 08, 2022, 06:00:14 pm ---
--- Quote from: SandyCox on May 08, 2022, 05:52:01 pm ---When applying circuit theory to the problem, either the law of conservation of charge or the law of conservation of energy is violated.
--- End quote ---
There is no such thing as conservation of charge. The conservation of energy is a law.
--- End quote ---
Look at section 1.5 of Haus and Melcher.
IanB:
--- Quote from: SandyCox on May 08, 2022, 05:52:01 pm ---When applying circuit theory to the problem, either the law of conservation of charge or the law of conservation of energy is violated.
--- End quote ---
If the two capacitors form a closed system then charge is conserved within that system. The model then indicates that electrical energy is not conserved, but this says nothing about total energy. Energy could be converted to other forms such as heat, or it could cross the system boundaries and leave. Neither of these possibilities violate causality.
If you look at the situation from a physics perspective, the connecting together of the two capacitors is an irreversible process, which therefore causes an increase in entropy. This increase in entropy translates to a decrease in the free energy of the system, which means you can get less useful work out of the two capacitors after you have joined them than you could get out of the one capacitor at the start.
electrodacus:
--- Quote from: SandyCox on May 08, 2022, 06:09:30 pm ---Look at section 1.5 of Haus and Melcher.
--- End quote ---
??? Never heard of them before now and likely for a good reason.
People seems to confuse charge with energy.
Energy is the one that can not be created or destroyed just converted from one form to another.
SandyCox:
--- Quote from: IanB on May 08, 2022, 06:12:59 pm ---
--- Quote from: SandyCox on May 08, 2022, 05:52:01 pm ---When applying circuit theory to the problem, either the law of conservation of charge or the law of conservation of energy is violated.
--- End quote ---
If the two capacitors form a closed system then charge is conserved within that system. The model then indicates that electrical energy is not conserved, but this says nothing about total energy. Energy could be converted to other forms such as heat, or it could cross the system boundaries and leave. Neither of these possibilities violate causality.
If you look at the situation from a physics perspective, the connecting together of the two capacitors is an irreversible process, which therefore causes an increase in entropy. This increase in entropy translates to a decrease in the free energy of the system, which means you can get less useful work out of the two capacitors after you have joined them than you could get out of the one capacitor at the start.
--- End quote ---
That's very true. The problem is that circuit theory, on its own, cannot explain how this energy is converted from one form to another. It is problems like these that indicate that we need a deeper understanding, i.e. electrodynamics.
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