[Il Divo]

Hey all, was hoping to get a final clarification on something. I'm looking to study Photovoltaics and been having a good time reading the theory so far, but thought it might be a good idea to brush up on electric circuits as well as galvanic cells.

I just wanted some clarification regarding battery composition and how electrons flow in a circuit.

So your basic battery/voltaic cell is composed of an anode and a cathode. Your anode could be Zinc metal which is oxidized and your cathode will be Copper ions which will be reduced. A salt bridge is typically used to counter the positive ions generated. An external circuit is used so that electrons flow from the anode to the cathode and by attaching this circuit to some resistor (say a lightbulb) this generates light prior to reaching the copper atoms. That's at least how I thought a basic battery worked.

I recently read this:

In a certain sense, an electric circuit is nothing more than an energy conversion system. In the electrochemical cells of a battery-powered electric circuit, the chemical energy is used to do work on a positive test charge to move it from the low potential terminal to the high potential terminal. Chemical energy is transformed into electric potential energy within the internal circuit (i.e., the battery). Once at the high potential terminal, a positive test charge will then move through the external circuit and do work upon the light bulb or the motor or the heater coils, transforming its electric potential energy into useful forms for which the circuit was designed. The positive test charge returns to the negative terminal at a low energy and low potential, ready to repeat the cycle (or should we say circuit) all over again.

This seems rather different from how I envisioned in the process. I was wondering if someone could tell me what parts I got right/wrong and (visually) how they imagine a battery functioning.

Thanks.

[Borek]

A salt bridge is typically used to counter the positive ions generated.

Not exactly - salt bridge is used to close the circuit. Ions from the salt bridge flow into the cell to keep it neutral after the electrode reaction adds/removes electrons, so what you wrote is not entirely incorrect, but it is only addressing part of the problem.

Other than that nothing cries out loudly "I am wrong", and I don't see contradiction between two explanations you posted, they just address the same system from different points of view.

[Il Divo]

A salt bridge is typically used to counter the positive ions generated.

Not exactly - salt bridge is used to close the circuit. Ions from the salt bridge flow into the cell to keep it neutral after the electrode reaction adds/removes electrons, so what you wrote is not entirely incorrect, but it is only addressing part of the problem.

Other than that nothing cries out loudly "I am wrong", and I don't see contradiction between two explanations you posted, they just address the same system from different points of view.

I think part of my confusion is that I'm seeing that it describes the positive charge as repeating the circuit, which I thought was contradictory. And I've also seen other sources similarly describe the electrons as repeating the circuit once they reach the Cathode. I thought essentially once the electrons reach the Cathode, their reaction is complete. The battery dies when there doesn't remain enough material to perform oxidation/reduction.

Once the electrons reach the Cathode, in some way, are they passing through the electrolyte to return to the anode?

[Borek]

"Test charge" is just a theoretical construct, it tells you what happens in any particular point, it doesn't necessarily describe the real behavior of any particular charge in the circuit.

Electrons are indistinguishable, so you can't say whether any particular electron circles the circuit more than once. Actually I doubt any electron travels further than just a few mm from its starting position. What you can be sure is that they all shift. Some pass the phase boundary between the electrode and the solution, after that they will travel not as electrons, but as part of an ion (or not, if the product is a neutral molecule in the solution). What is important is that the charge - in any form, be it ions, or free electrons - can travel in some way at any point of the circuit.

[Il Divo]

"Test charge" is just a theoretical construct, it tells you what happens in any particular point, it doesn't necessarily describe the real behavior of any particular charge in the circuit.

Electrons are indistinguishable, so you can't say whether any particular electron circles the circuit more than once. Actually I doubt any electron travels further than just a few mm from its starting position. What you can be sure is that they all shift. Some pass the phase boundary between the electrode and the solution, after that they will travel not as electrons, but as part of an ion (or not, if the product is a neutral molecule in the solution). What is important is that the charge - in any form, be it ions, or free electrons - can travel in some way at any point of the circuit.

Okay, that definitely helps a lot. Thank you very much. I was thrown for a bit of a loop. I thought I had a pretty good idea of how a basic battery works, so when I saw that bit about charges cycling my head was spinning.