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basic battery question

C

Christian Blondin

Jan 1, 1970
0
Being fairly new to electronics, and not an engineering student, I found
out something that I can't explain: why can't current go from one battery
to the other, such as this:


----------------------------
| |
| + |
--- -
- 1.5V ---
--- 1.5V -
- ---
| + |
| |

I know that if I connect the two other poles together I get an instant
short circuit.

I thought on the + side of the battery there were always 'holes', and in
the - side excess electrons. Normally they should flow from one to the
other. Is it something chemical?
 
C

CFoley1064

Jan 1, 1970
0
Subject: basic battery question
From: Christian Blondin [email protected]
Date: 2/13/2004 8:51 AM Central Standard Time
Message-id: <[email protected]>

Being fairly new to electronics, and not an engineering student, I found
out something that I can't explain: why can't current go from one battery
to the other, such as this:


----------------------------
| |
| + |
--- -
- 1.5V ---
--- 1.5V -
- ---
| + |
| |

I know that if I connect the two other poles together I get an instant
short circuit.

I thought on the + side of the battery there were always 'holes', and in
the - side excess electrons. Normally they should flow from one to the
other. Is it something chemical?

Current flows from one place to another based on differences in potential --
i.e. voltage. Since they're both 1.5V batteries, you won't see much difference
in potential between the two. However, real-world batteries do have minor
differences in voltage, dependent on such things as age and use. So you will
get some current flow between batteries if you do this.

Generally, hooking up batteries in parallel like this is *not* a good idea --
they're not made to do that. If you hook up two batteries in parallel like
this, you'll almost never get twice the "life" (amp-hours -- amps of load
current * number of hours, the measure of battery capability) out of them as
you would from a single battery. Sometimes you can even damage one battery,
leading to less "life" (total amp-hour output) than you would from a single
battery on its own, because the second damaged battery acts like a draining
load on the first, using up energy. If this is happening, you may find that
one of the batteries is getting warm or hot -- it's being heated by the other.

Good luck
Chris
 
O

Olaf

Jan 1, 1970
0
Being fairly new to electronics, and not an engineering student, I found
out something that I can't explain: why can't current go from one
battery to the other, such as this:


----------------------------
| |
| + |
--- -
- 1.5V ---
--- 1.5V -
- ---
| + |
| |

I know that if I connect the two other poles together I get an instant
short circuit.

I thought on the + side of the battery there were always 'holes', and
in the - side excess electrons. Normally they should flow from one to
the other. Is it something chemical?

of course a battery is a chemical device, but that's not the point here.
You seem to think of a battery as having to sides, one with to much
electrons and one side with to little. Though this can explain some
circuit behaviour you'ld better think of a battery as a charge pump. The
charge is made up of electrons and the battery creates a force. But a
battery cannot compress electrons inside a wire or inside a battery.
Neither can it suck them out of a piece of wire. A battery just tries to
move the file of electrons inside the wire and the other components.

Now it should be clear why nothings happens (I hope ;-): the left battery
tries to push electrons inside the lower piece of wire (not possible), the
right battery tries to suck electrons out of the lowers right piece of
wire (not possible) and they both try to move the electrons in the upper
piece from right to left. But these electrons have no place to go, and
there aren't any electrons available on the right side to fill them up. So
nothing happens.

And in correction to Chris's post, the batteries in your circuit are
connected in series and there is no problem in this. Most battery operated
devices use batteries this way. Your circuit may be considered as a single
3.0V battery.

hope this clarifies?

bye, Olaf
 
G

grahamk

Jan 1, 1970
0
Olaf said:
of course a battery is a chemical device, but that's not the point
here. You seem to think of a battery as having to sides, one with to
much electrons and one side with to little. Though this can explain
some circuit behaviour you'ld better think of a battery as a charge
pump. The charge is made up of electrons and the battery creates a
force. But a battery cannot compress electrons inside a wire or
inside a battery. Neither can it suck them out of a piece of wire. A
battery just tries to move the file of electrons inside the wire and
the other components.

Now it should be clear why nothings happens (I hope ;-): the left
battery tries to push electrons inside the lower piece of wire (not
possible), the right battery tries to suck electrons out of the
lowers right piece of wire (not possible) and they both try to move
the electrons in the upper piece from right to left. But these
electrons have no place to go, and there aren't any electrons
available on the right side to fill them up. So nothing happens.

And in correction to Chris's post, the batteries in your circuit are
connected in series and there is no problem in this. Most battery
operated devices use batteries this way. Your circuit may be
considered as a single
3.0V battery.

hope this clarifies?

bye, Olaf

Redraw the circuit by sliding the RH battery so that it sits on top of the LH battery.
You now have a 3 volt battery with positive and negative terminals.
No current can flow until you connect a device such as a 3 volt lamp between these terminals.
 
C

Christian Blondin

Jan 1, 1970
0
Thank you all for your replies, and long live newsgroups.
 
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