KB6NU's Ham Radio Blog

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Which way does current really flow?

Posted: 19 Feb 2018 11:15 AM PST
http://feedproxy.google.com/~r/kb6nu...m_medium=email


Last month, I received an email from a reader about the new Tech question
pool. He pointed out a number issues with the questions, including some
grammatical errors and inconsistencies. For example, he noted that in some
questions, they used DC and in others, just dc.

It was that eye for detail that prompted me to ask him if hed proofread the
updated version of my No Nonsense Technician Class License Study Guide.Â* I
offered to pay him, but he replied,

You do sell [your study guides], but you also make PDFs available for free.
Since my #1 motivation to help would NOT be money, for now lets just
evaluate how good a job I can do on an unpaid trial basis.

Then, he took me to task:

Right away I saw something there that I didnt fully agree with. You
casually say that current flows from Positive to Negative (with cool
accompanying directional arrows), without any accompanying qualifying
statement. Over the years I have looked at ALL the views on the subject.
Positive to Negative is NOT what I was taught 48 years ago, and I have
never seen a good reason to change my view. I even created a poll on QRZ to
see what the general consensus would be on there. The Positive to Negative
crowd did take an early lead, but my fellow Neanderthal flat earth
adherents came through and powered Negative to Positive on to the victory.
If you make a blanket statement that is not universally accepted, I will
challenge it.

In a subsequent email, he pointed me to a Nuts n Volts article, Which Way
Does Current Really Flow? and asked my opinion. In the article, the author,
who is a ham by the way, does a good job of explaining the various types of
current flow.

I agree that in electronic circuits electrons flow from negative to
positive, but it really doesnt matter. I agree with the commenter Mike
Huddleston who says,

This is a silly argument. Its like comparing apples and oranges and
challenging people to take sides.

Electron flow is not current flow. Electron flow is easy to understand, an
actual physical property, and a real help in understanding vacuum tube
operation. But it falls apart when one needs to understand complex
electronic systems.

[Conventional] current flow is a mathematical abstraction. It is defined as
a net flow of positive charge, irrespective of the polarity of the physical
charge carriers whether electrons, holes, positive or negative ions, or
whatever.

When looking at any circuit containing a resistance with a voltage across
it, conventional current through that resistor says that the voltage drop
occurs as the current through it meets resistance. On the other hand, in
negative (electron) flow, a voltage INCREASE will correspond to the current
flow through it, clearly violating physical laws. Conventional current flow
is consistent with the laws of physics and those of other engineering
disciplines.

You are correct that engineers, professors and scientists use conventional
current flow. That is not because they are too obtuse to understand
electron flow; I assure you they fully understand it. It is because in
their world they have to solve more general problems involving complex math
and science, and, again, conventional current flow is consistent with
physical laws.

It is unfortunate that electron flow and current flow are so often
confused. They both have their place.

I thought I’d have a look and see what the ARRL Handbook has to say about
current. In the 1963 edition, they don’t mention electron flow at all. They
have one diagram showing the direction of current flow in both series and
parallel circuits, but the voltage source has no polarity. It’s simply
labelled “Source of E.M.F.� Diagrams giving practical examples of series
and parallel circuits do include a battery, and if the reader were to mash
up the two diagrams, they would conclude that current flows from the
positive terminal to the negative terminal.

The most recent edition of the Handbook that I have is the 2005 edition (it
might be time to get another copy!). It says,

Electrons move from the negative to the positive side of the voltage, or
EMF, source. Conventional current has the opposite direction, from positive
to negative. This comes from an arbitrary decision made by Benjamin
Franklin in the 18th century. The conventional current direction is
important in establishing the proper polarity sign for many electronics
calculations. Conventional current is used in much of the technical
literature. The arrows in schematic symbols point in the direction of
conventional current, for example.

Having said all that, I really don’t see that there’s much of a controversy
here. I did learn to think of current as conventional current in college,
although it was mentioned that electrons actually flow in the opposite
direction. Using the concept of conventional current has never seemed to
hold me back. I’ve been able to design circuits and repair electronic
equipment thinking that current flows from positive to negative.

I dont know what this all means for the next edition of my study guide. I
do hope that my friend decides that hell proofread my study guide in spite
of the fact that Im an adherent of conventional current flow, and hes an
electron current flow guy. I am thinking of including a sidebar, similar to
the paragraph above from the 2005 Handbook explaining the two ways of
looking at current flow, although thats kind of a departure from my no
nonsense style.

What do you think?



The post Which way does current really flow? appeared first on KB6NUs Ham
Radio Blog.

In article , rec-radio-amateur-
says...
You are correct that engineers, professors and scientists use conventional
current flow. That is not because they are too obtuse to understand
electron flow; I assure you they fully understand it. It is because in
their world they have to solve more general problems involving complex math
and science, and, again, conventional current flow is consistent with
physical laws.

It is unfortunate that electron flow and current flow are so often
confused. They both have their place.



It would have been much simpler if one of the old guys like Ben Franklin
or maybe another had not made the mistake and gotten it wrong around 200
years ago. Which ever one it was thought the current went from positive
to negative.

At a later time it was discovered the electrons actually went the
opposit way.

For most of the common calculations, it is just assumed the current goes
from positive to negative.