A question on batteries.

[Moderhater]

So this will probably come off as a odd question but I just started learning electronics.

If I have two batteries that are the same condition and same voltage ( two identical 9 volt batteries ), Why can't I use the negative terminal of one, and the lead of the other?
If the state of the metals in each terminal is set, and a negative has more electrons then the lead terminal, then why cant it transfer to the other batteries lead?

I would of thought this would be an easy question to answer, but maybe I don't know how to word the question cause for the first time, google turned up nothing.

 

[davelectronic]

Hi Welcome to the forum, iam not totally understanding your description on what your trying to achive, i know parallel and series connection of batterys, just your description has me baffled.

 

[Moderhater]

Thanks for the welcome.

I'm confused on how batteries work really.
Forgive me it's a crude drawing but...

Of course in the top pictured, there would be 18volts, but I don't get why the bottom wiring
wouldn't produce 9 volts.
The negative terminal holds a negative charge and the other batteries positive terminal is a lead.

 

[davelectronic]

Hi again, your top picture is a series connection of the two batterys, your second drawing can be series or parallel, but there are no leads on one terminal of each battery, so no voltage flows.

 

[Moderhater]

I think I might of asked the question wrong.
I'm still not sure how to word it, but thinking about it more, I think my question
might not be so much an electronics question but more a question of how electricity
really works.

The understanding I left school with of electricity was that any "matter" that holds a negative
charge will release any excess electrons to any matter that has less electrons then the
atoms balanced state.

With that image of how dc power flows I can't see in my mind why the negative wouldn't
pass to any positive terminal.

Maybe I'm way off in interpreting the pictures I see of how electrons flow, or maybe it is to do
with the chemical balance of a battery. To be honest, I'm not too good with terminology
so it's hard to describe.

 

[davelectronic]

I know posative electrons flow around a circuit, and return via a negative route, but i dont do the whole lab thing, maybe another member can help you on the electrons at an atomic level questions.

 

[(*steve*)]

Electrons (negatively charged) flow along conductors in a circuit. They exit at the -ve terminal of a battery go through the circuit and return to the positive electrode of the mattery.

If there is no connection between the positive electrode and the negative (usually through more than just wires -- you may have lamps etc) then no current can flow.

In your first example the voltmeter completes the circuit and current can then flow. The voltmeter measures the difference in potential -- in that case 18 volts.

In the second case the voltmeter does not complete the circuit. The circuit is open between the two batteries. Since no current can flow, there is effectively no potential difference betwen the points the meter is connected to. Effectively neither wire is more positive or negative than the other.

 

[davenn]

I think I might of asked the question wrong.
I'm still not sure how to word it, but thinking about it more, I think my question
might not be so much an electronics question but more a question of how electricity
really works.

The understanding I left school with of electricity was that any "matter" that holds a negative charge will release any excess electrons to any matter that has less electrons then the atoms balanced state.

welcome
not quite right
ALL matter is made up of positive and negative charges, and barring any external influences the positive and negative charges are balanced. lets take a block of plastic and a block of copper. The they both are made up of atoms a nucleus made up of protons and neutrons surrounded by a "cloud" of orbiting electrons. The number of electrons for each atom = the number of protons in each atom nucleus (core). That goes for both the insulator , the plastic and for the copper a good electrical conductor.
So why you ask does the copper conduct and the plastic not conduct.
Well very simply without getting into deep physics.
Its because in some materials, like metals and a few other things, have a lot of loosely bound electrons in their outer shells ( electrons form "shells" (layers) around the nucleus. These electrons are able to reasonably freely move between the atoms. In an insulator it is the opposite and those outer shell electrons are not free to move. so when a current ie. a supply of electrons is applied to the copper block, say from a battery negative terminal, electrons are "pushed" The push comes from the voltage ( the potential difference between the terminals of the battery or other supply) in from one end of the block electrons start moving along from atom to atom the electrons are attracted to the positive end of the battery terminal connected to the other end of the copper block, where there is a deficiency of electrons.

With that image of how dc power flows I can't see in my mind why the negative wouldn't
pass to any positive terminal. Maybe I'm way off in interpreting the pictures I see of how electrons flow, or maybe it is to do with the chemical balance of a battery. To be honest, I'm not too good with terminology so it's hard to describe.

Electrons will flow through the wire and a current of electricity is produced. Inside the battery, a reaction between chemicals take place. But the reaction takes place only if there is a flow of electrons. Batteries can be stored for a long time and still work because the chemical process doesn't start until the electrons flow from the negative to the positive terminals through a circuit.

hopefully that helps a bit

cheers
Dave

 

[davenn]

Now playing with static electricity is a slightly different ball game.

we can use items normally considered insulators ... like a rod of nylon and rub it with a lump of fur. and generate a charge on that rod. From memory this strips the free electrons from the rod leaving it positively charged and when we bring the rod near a neutrally charged or a balanced charged material we can get a transfer of charge between the material and the rod.
Same as when you feel a zap touching a door knob after walking across a carpeted floor

Dave

 

[Merlin3189]

If we go with the idea that there is a +ve charge on one terminal of one battery and a -ve charge on the other terminal of the second battery, then I think you would get a current flow as you said.
BUT if there's no where for the charges to go when they get to the other battery, you will very rapidly build up a charge on the other battery to oppose the flow. So it will stop. And this will happen so quickly that you'd be hard pressed to notice the initial flow at all.

You need the other connection (where the charge is such as to push charges from the second battery to the first) to keep the total charge on each battery the same. In a CIRCUIT the total amount of charge on any component (be it battery, capacitor, LED, bit of wire or whatever) must stay constant. You can push charge out of one terminal, but you must draw in an exactly equal amount through the other terminal(s) - or vice versa.

This is what Kirchoff explained over 150yrs ago. Look him up.

 

[Moderhater]

Thanks for all the answers guys, I think I understand it now, well, understand it a little
better.
Thanks for the recommendation Merlin, Reading on Kirchhoff's work for the last hour
has been very enlightening.

The question I had came up while I was playing with a few circuits so I google'd for
electronic forums and came across here, I like this place so expect to see me
around from time to time. Cheers!

 

[sherjan]

[dear
for the flow of electrons in a circuit it is mandatry that the circuit should be closed i.e the electron flows from one terminal to other than there should also be also a reverse case. means that from positive to negative and from negative to positive.
in condition about u asking, the circuit is not close the current will not flow.