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I am currently reading about emf and internal resistance and I came across this paragraph. What does this mean?

Paragraph

Figure mentioned in the paragraph

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4 Answers 4

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Notice that in the passage there is the statement, To understand the significance of $\mathcal E$, with $\mathcal E$ being the emf of the cell I assume?

Electrode $P$ is at a higher potential than electrode $N$ and thus through the resistor the (conventional) current flows from the higher potential towards the lower potential.

However, within the cell the current flows from the lower potential towards the higher potential, $B$ to $A$.
This is because within the there are electrochemical reactions and "chemical" energy is being used to force the electric charges move from a lower to higher potential thus increasing their electric potential energy.
One can imagine the cell being a pump which raised the potential energy of the charges.

Thus, electromotive force is all to do with the conversion of one form of energy, chemical in a cell, light in a photocell, mechanical in a generator, etc into "electrical" energy.
The energy converted into electrical energy per unit charge flow is a measure of the emf, with $1$ joule of converted energy per coulomb of charge flow being called $1$ volt.

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  • $\begingroup$ So which is the true current,the conventional current which flows from P to N or the current which flows from N to P $\endgroup$ Commented Jun 4, 2023 at 7:43
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    $\begingroup$ @SanjitVignesh The "true" one is the one from N to P since current is carried by electrons. But it's just a convention anyway. We could build a completely equivalent physical system where electrons carry positive charge and the conventional current would be the "right" one $\endgroup$ Commented Jun 4, 2023 at 7:49
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It is just saying that the current I goes from C to D, and a current of the same size goes from B to A. The circuit is thus a closed loop.

What the electrolyte and the cathode and anodes are doing is rather interesting.

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I think the arrow of the current to the left that points to the right, is wrong in the diagram. "The same current flows through the electrolyte but from N to P" is where you generate the potential difference in the cell.

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The lines just say that the complete circuit is closed or circular. Or you have to say which part you do not understand.

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