Voltage Increases When Connecting Multiple Batteries

[sophiecentaur]

That's what Potential Difference is all about. Although, with an attractive force, the Energy is defined as Negative. For a wire made of a highly conductive metal the PD across the length will be tiny.

 

[scientifico]

the Energy is defined as Negative

mean that conventionally the energy flows from the plus to the minus?

For a wire made of a highly conductive metal the PD across the length will be tiny.

What do you mean for "across the length" ?

 

[sophiecentaur]

mean that conventionally the energy flows from the plus to the minus?

What do you mean for "across the length" ?

Negative energy applies to an 'attractive' system in which energy is produced when two objects get closer - a waterfall produces useful energy because the (gravitational in this case)potential energy is less at the bottom than at the top. I am not referring to the electrons specifically having a negative charge. You could just as easily talk about positive charges moving to the negative terminal (the conventional way).

By "Across the length" I mean 'as opposed across the width' of the conductor. The PD over the whole length of the conductor is still small.

 

[Windadct]

IMHO - the "Negative Energy" term is really just confusing this issue. Energy moves (converted) from one system to another, a positive or negative reference only applies to the point of observation or the difference in two or more states ( top of the waterfall vs bottom of the waterfall, battery before the current flows vs after the current flows) They have less energy, but they do not negative energy.

For battery energy does NOT flow from one terminal to another, IN the battery a chemical system has potential energy stored ( I would never think of this as negative) and it creates EMF ( Electro Motive force / voltage) but a force alone is not energy but in pretty much all systems indicates that there is some energy present. In the simplest case when the positive terminal and negative terminal of the battery are connected by some form of a conductor, the chemical potential energy is converted into electrical energy - in the case of a simple wire - essentially ALL of the energy is converted to heat energy.

You can refer to the difference of energy - being negative.

Back to the OP - two batteries in series, the Electro-Motive Force (voltage) is added - the force sums as does the potential energy of the two batteries. Note if you have 2 equal batteries - you always have 2 x the energy - how you connect them is irrelevant.
In the waterfall analogy - think of 2 waterfalls - on on top of another - if the water is 2x as high - it has 2 x the potential ( relative to the bottom of the waterfall)

As for the Potential Difference (PD) "Across the Length" of the conductor - it has to equal the potential applied - assuming from the battery, so I am missing the "is still small" reference. ( Since a battery is not a perfect device - it also has internal resistance - which will see some voltage if you short circuit the battery with a wire - but that discussion is also off topic of the OP)

Sorry to bring some "Negative Energy" to the thread.

 

[scientifico]

An high potential difference pratically means that more work is relased when a coulomb move from the lower point to the higher, and a low PD less work for the same coulomb?
Why in some places is written that the energy is needed to move a charge istead of relased when a charge move, who is right?

When I connect the 2 poles of a battery the first electrons moving are the one near the positive but they can be too the electrons of the metal wire right?

 

[Windadct]

You are correct that moving a charge across a lower PD ( field) absorbes or releases less energy then in a higher PD ( field). In all cases energy is needed ( source ) and is transferred to something else. "Energy needed" "consumed" etc are all a matter of perspective (are you the circuit or the battery)- for this a rechargeable battery is a good model - you have to ADD energy to the battery to charge it - and it delivers energy when it discharges. This is a basic physics model.

The point of the battery is that it generates a voltage, this voltage acts on all of the electrons in the conductor the same way - there is not more action near one terminal of the battery.

It is the presence of the voltage that acts instantly ( technically some speed slightly slower then the speed of light across a conductor) - this voltage make (pushes/pulls) all of the electrons in the conductor at the same time.

Thinking of how the electrons move in an conductor - is 2 -3 levels or more than is required to discuss the OP. When you put 2 batteries in series the voltages add - this is a basic circuit question. How electrons flow in a conductor when a voltage is applied, is physical science ( still an electrical engineering discipline ) - but is not directly related to how a battery operates. Part of the beauty of Electrical Engineering is how well the real world application matches the theory AND how well the theory can be broken into very simple elements. So mixing the discussion between the three or four concepts in this thread - is really only making is much more difficult. Batteries/Energy/EMF/Electron flow - each requires their own study - then you can better understand how they interact - but in reality you almost never need to think of them all at the same time to solve any problem.

 

[scientifico]

The force that act on electrons is provided by the positive charges, so teorically if i connect a piece of wire only to the positive pole, is there a possibility that some electrons of the wire go to the +?

Thank you!

 

[sophiecentaur]

IMHO - the "Negative Energy" term is really just confusing this issue. Energy moves (converted) from one system to another, a positive or negative reference only applies to the point of observation or the difference in two or more states ( top of the waterfall vs bottom of the waterfall, battery before the current flows vs after the current flows) They have less energy, but they do not negative energy.

Yes, I have to agree with you there. It may be true bit it isn't really relevant.

This thread is a great example of one which is being driven by a diehard misconception about electrical energy transfer. The Schoolboy model of electrons along wires is so attractive and 'pictorial' that it makes people hang onto it long past the point where they should be looking for something deeper.

The fact is that Electrical Energy transfer is a very sophisticated process. There is no satisfactory description at an elementary level. Along with all the other difficult concepts in Physics (QM, Relativity etc,) , if you think you've 'got it', then you probably haven't.

I had a huge advantage in being 'taught' Electricity without the use of noddy electron picture models. You go straight into a simple mathematical treatment and it yields all the measurable behavior of circuits and emerge with confidence about those tangible things. Later on you talk about conduction and electron motion in a vacuum and the QM aspects of it all. At no stage was there any need to 'demand' an 'understandable' model.

The way things are going seems to be little more than the blind leading the blind (delivery of the Electricity Curriculum in School, for instance) and with no one being prepared to get down and dirty with some serious basic theory. "In my day" conversations like this were short and sweet because people accepted that they don't really get you anywhere.

 

[sophiecentaur]

The force that act on electrons is provided by the positive charges, so teorically if i connect a piece of wire only to the positive pole, is there a possibility that some electrons of the wire go to the +?

Thank you!

You are describing what is referred to as an Incomplete Circuit. No steady current will flow, of course. But when the wire is first connected, there will be a small (and just detectable) charge flow, until the fields balance out. If, instead of a wire, you use a pair of plates, closely spaced and with a large area (same thing conceptually) then you get a Capacitor and a very significant charge will flow which will 'charge' the capacitor until, again, the fields balance out.

 

[scientifico]

So if I just connect a wire to the positive pole (creating an incomplete circuit) there will be no steady current because the protons of the wire will not permitt the wire electrons to move away to the positive pole of the battery?
So, if the positive of the battery would have a very big potential difference and for example the wire is heated, is it possible to remove electrons from the wire?

Thank you!