[vhfpmr]

You would never normally do that with a battery though, the efficiency's only 50%.

Which is the best you can get...

No it isn't. With a series loss only the efficiency is Rl/(Rl+Rs), which is an asymptote to 100% as Rl tends to infinity. With a source that has series and parallel losses (eg a transformer), the load for optimum efficiency is the geometric mean of Rs and Rp (provided that Rs<<Rp).

[evan_au]

You will get the maximum power to an external load when that load's resistance is equal to the battery's.

This principle is very relevant in transmission lines (whether 50Hz or 5GHz), where the impedance is mainly capacitance and inductance (which don't absorb real power, like a resistor does).

However, when you have significant resistance, power dissipation in the source becomes a significant problem.
- If you dissipate 10W in your battery for very long, your battery might explode as the electrolyte vaporizes.
- In a nuclear power plant, if you dissipate 1 GW inside your alternator, it will quickly melt.
- In both cases, the design goal is to make the source resistance much less than the intended load resistance.
- That way, you transfer a greater % of the power to the load, and you avoid damaging the power source.

[scientizscht (OP)]

So the total number of Zn atoms that react per second are the same when the cells are in series (where the current is 5A) and when in parallel (where the current is 10A)?

Yes or no and what is that/these numbers?

[Bored chemist]

You start by arguing that there isn't any resistance,

Did you miss this bit?

if the load resistor is zero.

[Bored chemist]

So the total number of Zn atoms that react per second are the same when the cells are in series (where the current is 5A) and when in parallel (where the current is 10A)?

I have already pointed out a  number of times that batteries can't see the outside world.
A consequence of that is that they can not, even in principle, act differently depending whether they are in series or parallel because they don't "know" it..
So why are you asking if they do?

[alancalverd]

So the total number of Zn atoms that react per second are the same when the cells are in series (where the current is 5A) and when in parallel (where the current is 10A)?

Yes or no and what is that/these numbers?

Yes. Given that each Zn atom carries 2 electrons, I'll leave it to you to work out how many.

[alancalverd]

I have already pointed out a  number of times that batteries can't see the outside world.

I think you have confused the poor lad.  The battery does quite different things if the outside world consists of a short circuit (lots of ionic activity) or an open circuit (no activity). 

[Bored chemist]

I have already pointed out a  number of times that batteries can't see the outside world.

I think you have confused the poor lad.  The battery does quite different things if the outside world consists of a short circuit (lots of ionic activity) or an open circuit (no activity). 

True, but if it's delivering 10W then it's delivering 10W
The heat or reaction of zinc (and whatever the oxidant is) is a matter of thermodynamics, not electronics.

Also if it's delivering 5A then it's delivering 5A.
It doesn't know any better, so it eats up zinc at the same rate.

[vhfpmr]

You start by arguing that there isn't any resistance,

Did you miss this bit?

if the load resistor is zero.

No I didn't miss it.

You can't claim the resistance isn't changing when you switch from series to parallel just because it's hidden inside the cells.

[Bored chemist]

You start by arguing that there isn't any resistance,

Did you miss this bit?

if the load resistor is zero.

No I didn't miss it.

You can't claim the resistance isn't changing when you switch from series to parallel just because it's hidden inside the cells.

Yes I can.
It is 0.4 Ohms in each cell whether that cell is in series or parallel.

.
My point- I thought I had laboured it hard enough but, here we go again- is that the cell doesn't know what's happening outside. So each cell has a constant internal resistance. (OK in practice it's temperature dependent and slightly current + time dependent).

Cut to the chase.
Either tell us where I contradicted myself, or point out where I got the wrong numbers.

[vhfpmr]

Yes I can.
It is 0.4 Ohms in each cell whether that cell is in series or parallel.

In which case you'd have to apply the same logic to the voltage and current and say they're not changing either. My comment was in response to the OP who was talking about double voltage with half current, but no change in resistance.

My point- I thought I had laboured it hard enough but, here we go again- is that the cell doesn't know what's happening outside. So each cell has a constant internal resistance.

Yes, I know, but that’s just repeating what I’d already said here:

Snip.JPG (181.46 kB . 1528x617 - viewed 1457 times)

My original point to the OP was that you can't double the voltage in series without doubling the resistance, and you can't double the current in parallel without halving the resistance as he seemed to be arguing.

[Bored chemist]

In which case you'd have to apply the same logic to the voltage and current and say they're not changing either.

You start by arguing that there isn't any resistance,

Did you miss this bit?

if the load resistor is zero.

No I didn't miss it.

It seems you missed it again.

There really is a difference between the current in a cell of a parallel array and the current in the load connected to them.
And there really is a difference between the open circuit voltages of a single cell and a pair of cells in series.

But 0.4 ohms is still 0.4 ohms.

Yes, I know, but that’s just repeating what I’d already said here:

...

Which was just you repeating what I had said here

It is important to recognise that the cells do not have eyes.

What you and the  OP seem to have in common is a failure to distinguish clearly between the fixed internal resistance (which, he misunderstands- that doesn't help) and the load resistance- which one can vary at whim.

[alancalverd]

Vhf - I think your diagrams are adding to other folks'  confusion! The cell symbol looks like a voltage source in parallel with a resistance, whereas a cell actually behaves as an ideal (zero-impedance) voltage source in series with a resistance. It's OK for your simulator which knows what it is talking about, but not for those whose physics comes from textbooks!