common sense?? Prolly. Need answer.

Posted: Tue Mar 18, 2008 10:24 am

I'm studying basic electronics from the sound reinforcement handbook and I think I see an error in the book, so i'm kind of worried i might not learn the material right. I need to to find out about current flow and its direction. So:

If I put a 9v battery on my tongue, does the current flow from positive > tongue > negative or does it flow from negative > tongue > positive?

The book says it would flow from negative, but I watched a video from a university class on electricity (you tube) that said that electricity flows from the positive.

Thats my pickle.

Posted: Tue Mar 18, 2008 10:27 am

ELECTRON flow is from negative to positive... e.g. current

Voltage flow therefore is from positive to negative.

Posted: Tue Mar 18, 2008 10:31 am

I must have the attention span of a freaking rock, because after you reading your post i see your answer above the diagram in the book.

Good times.

Thanks!

Posted: Tue Mar 18, 2008 10:48 am

This is an area of continued confusion, of no fault of your own.

"Conventional" diagrams show current flow from the positive to the negative terminal. The reason is entirely historical, because that what seemed appropriate. It was only after significantly more was learned about what was happening at the subatomic level that physicists and engineers determined that the electrons, which are negatively charged are migrating, ie flowing.

Some college textbooks on electronic therory are published in two versions of the text, with one showing conventional and and the other version showing actual current flow.

Posted: Tue Mar 18, 2008 10:51 am

In response to Madmax

Actual current flow (not "conventional") is from negative to positive.
I have never heard the term flow used with respect to voltage. Voltage is equivalent to pressure, but it is the current that flows.

Posted: Tue Mar 18, 2008 10:55 am

Either way it hurts like hell when you put a 9V on your tongue. Twisted Evil

I knew a really crazy guy who did it all the time "for fun." I wonder how his taste buds are these days..... Rolling Eyes

Posted: Tue Mar 18, 2008 11:01 am

On a historical note, the convention of the sign of charge is due to Ben Franklin. His one-fluid model of electricity is arguably the first important contribution to science by an American. Now that we understand things better at a subatomic level it is common to refer to current as the flow of "holes" where electrons are absent.

If you are mathematically inclined, you can remember the convention that the electric field is negative the gradient of the voltage (so it points from positive to negative voltage), and the current is proportional to the electric field.

So yeah, it's not common sense at all. Requires memorization of arbitrary conventions.

Posted: Tue Mar 18, 2008 12:23 pm

In the standard definition, current flows from a positive terminal to a negative terminal. In an ordinary conductor, this current flow actually is made up of negatively charged electrons flowing the other way.

Voltage does not come into it, other than being the driving force behind the current flow.

Posted: Wed Mar 19, 2008 12:04 am

Wow, I never expected all this. So then which way does the 9V travel through my tongue and why? (as if you were describing it to a 5 yr old)

Posted: Wed Mar 19, 2008 12:11 am

I guess, in a nut shell, it's difficult to say whether electricity is coming or going?

Posted: Wed Mar 19, 2008 12:51 am

Space wrote:

I guess, in a nut shell, it's difficult to say whether electricity is coming or going?

Going. As in, "It's going to make your tongue fall off if you keep doing that"...

Posted: Wed Mar 19, 2008 3:17 am

Halifaxsoundguy wrote:

Wow, I never expected all this. So then which way does the 9V travel through my tongue and why? (as if you were describing it to a 5 yr old)

Maybe this will help:

http://www.eskimo.com/~billb/amateur/elecdir.html

Posted: Thu Mar 20, 2008 8:58 pm

JoeH wrote:

Either way it hurts like hell when you put a 9V on your tongue. Twisted Evil

I knew a really crazy guy who did it all the time "for fun." I wonder how his taste buds are these days..... Rolling Eyes

Maybe we have a different description of pain. I think it tickles. ha

Posted: Thu Mar 20, 2008 9:21 pm

And it's a hell of a lot quicker than searching for the battery tester!

Posted: Fri Mar 21, 2008 8:12 pm

The Theorem of Bent
== Put to the test ==

"Hmm...my car battery seems to be dead."

This topic sponsored by: