# Why is there no current flow when I connect two opposite terminals of two separate batteries?

I don't understand this..maybe there is something wrong with my understanding of battery or electricity.

I am learning about electricity more deeply this time. So please spare with me.

So lets begin with what I know:

• follow of current occurs when there is voltage drop.
• voltage drop happens when there is imbalance in charge.
• a battery is basically two separated chemicals. One side with electrons to spare and other side that needs electron to balance itself. which is imbalance in charge.
• When both sides are connected + side snatches electrons from - side. (And if there is a medium, conductor, then first electrons are taken from conductor that in turn snatches from - side, which not being able to keep electrons lose them and give up those electrons, we label it as excessive.)

The analogy i was taught with used marbles in pipe... When one side has excessive marbles And this pipe is connected to other side that has no marbles the marbles will instantaneously start falling out so even though marbles from container with excessive marbles haven't traveled there yet, they still start falling because filled side marbles are pushing marbles in pipe and which in turn push the last marbles in pipe out.

1st, Aren't electrons pulled by atoms that can use more electrons, and not move because one side is overfilled with electrons so they can't wait to push some out.

Questions:

1. if I connect a conductor to positive side of a battery, shouldn't it make all electrons/marbles fall into empty container as empty container will pull marbles as atoms need electrons?
2. if I connect two batteries' only opposite sides to each other shouldn't they drain (balance the each other out, cancelling all - & + charges)?

There exists a similar question here.

This description of a voltaic battery solves the conundrum which the question raises:

If one connects the + and - of the same battery with no resistance, one shorts and discharges it anomalously. There should always be a resistance ( the lamp in the drawing) on the same battery.It is clear in the diagram that a chemical path exists, a current of ions that closes the circuit and current flows.

A chemical circuit has to be closed for current to flow. Two different batteries have two different chemical flows . Electrons that might leave the anode to go to the cathode of the other battery cannot close the chemical circuit of the parent cell because the ions have no reason to move as no charge has gone to the copper cathode of the original cell. At the same time the second cell is at the same fix , as no chemical circuit is closed there too, no charge has left the zinc anode, no motion of ions possible.

• :Could you tell why we use electrolyte?I'm really confused where the oxidation,reduction etc takes place.To be honest I know that the flow of electrons(from zinc metal) are produced by the attraction of electrons towards the protons(copper metal) as seen in this video.I can't get why do we need an extra potential to make the current flow and why do we use an electrolyte that has no role in flow of electrons.Could you help me. – justin Apr 18 '16 at 11:06
• @justin electrolyte provides charge mobility, in the link provided: "As a zinc atom provides the electrons, it becomes a positive ion and goes into aqueous solution, decreasing the mass of the zinc electrode. On the copper side, the two electrons received allow it to convert a copper ion from solution into an uncharged copper atom which deposits on the copper electrode, increasing its mass." – anna v Apr 18 '16 at 12:44
• :Sorry but I couldn't get how electrolyte provides charge mobility.Do you mean to say that due to the potential difference in the electrolyte,electrons get an energy to move from zinc rod to copper rode through the wire? – justin Apr 19 '16 at 6:24
• look at the diagrams, the electrolytes have electrons and ions that provide the current in the electrolyte and exchange copper and zinc – anna v Apr 19 '16 at 6:40
• :Yeah I could see that to obey the principle of electroneutrality the $Zn^{2+}$ ions are attracted by the $SO_4{2-}$ ions.Could you tell why does zinc losses two of it's electrons? – justin Apr 19 '16 at 6:56

It's common for almost all analogies to break down at some point when the phenomenon is understood at a deep enough level. In the very old days indeed electricity was thought of as a fluid and a concept of 'pressure' and 'flow' was used. However electrons are not marbles. Most commonly they move because they are in an electric field, not because anything is bumping into them. Now to answer your 2 questions it is simpler to understand a battery as a thing that exerts a potential difference (voltage) between the 2 terminals. The gradient (derivative) of the voltage is proportional to electric field:

1. If you connect a conductor to a battery terminal the conductor becomes the same potential as the battery terminal, and the potential difference becomes 0, so there is no electric field.

2. If you connect the - terminal of a battery to the + terminal of another battery, the contacts will be at the same potential (because they are conductors). Then the potential difference between the 2 contacts is 0 and again there is no electric field.

• about 2, why is potential energy zero when side has excessive and other side lacks electrons. Why there is no potential here. – Muhammad Umer Dec 30 '13 at 2:54

Under the scenario you presented, all you've done is made a bigger battery. Which is just sitting there, so there is no current flow. If you open up a standard 9 volt rectangular battery you will find six 1.5 volt cells connected in series, i.e. exactly as you described.