Explaining Negative Particles & Magnetic Fields

[PiRsq]

I've read in my textbook in the elecromagnetism chapter, when a particle is negative and goes through the magnetic field the velocity is opposite to the current...I don't really understand this, can someone please explain this?

 

[kartiksg]

Direction of current is taken to be the direction in which positive charges move in a wire. We know that positive charges do not flow but the negative ones (electrons) do. These charges move in a direction opposite to the direction in which the positive charges were supposed to move. As an anology, you can imagine this.. if positive charges are spontaneously moving from point A to B, it means that B is at a lower potential (negative) and A is at a higher potential (positive). If a negative charge were kept instead of the positive one, it would move from point B to point A (reverse direction). Since we usually measure magnetic fields and its effects based on 'currents', we must adhere to the conventional definition of current. Since an negative charge is always urged to move in a direction opposite to that of conventional current, we reverse the velocity of electrons when calculating effects on it by magnetic fields.

Hope I was clear.

Kartik

 

[himanshu121]

It will be very helpful if you study the Halls effect, and experiments which determines the charge carriers as electrons

 

[Integral]

Direction of current is taken to be the direction in which positive charges move in a wire.

I was taught electronics, by the US Navy, with negitive current flow. The direction of current flow is intirely arbitray, it is not clear to me why US achedemia insists on teaching a positive current flow.

 

[lethe]

Originally posted by Integral
I was taught electronics, by the US Navy, with negitive current flow. The direction of current flow is intirely arbitray, it is not clear to me why US achedemia insists on teaching a positive current flow.

the best choice of all, in my opinion, would be if everyone could just rename the electron to be positive.

stupid ben franklin

 

[Integral]

Originally posted by lethe
the best choice of all, in my opinion, would be if everyone could just rename the electron to be positive.

stupid ben franklin

Yep!

Poor Ben, he had a 50-50 chance and blew it!

 

[lethe]

Originally posted by Integral
Yep!

Poor Ben, he had a 50-50 chance and blew it!

allow me to quote john baez:

Actually they said it has charge -1: an unfortunate convention which we can blame on Benjamin Franklin, because he was mixed up about which way the electricity flowed in a current. But what do you expect from someone who flies a kite with a key hanging on it during a thunderstorm, to attract lightning bolts? Dumb! But lucky: the next two people to try that experiment were killed.

 

[ObsessiveMathsFreak]

When Ben Fraklin first labeled charges as positive and negative, whatever way he went about it, he gave electrons negative charge and protons positive charge. Of course he didn't know about electrons and protons at the time, just the charges caused by an excess and shortage of electrons, which he didn't know about.

Anyway, having labeled his charges + and - he just then said, ok, charge flows from + to - . Unfortunate as we now know that it is only the electrons that flow any they carry their - charge to + areas. However at the time no one could find any difference at all between + and - charges.

The reason we still use the idea that current flows from + to - is because transistors are easier to understand, if viewed in this way.
Amoung other things. Of course if w tried to change it now, half of the world would use the old system and half the new and sooner or later ... BOOOOMMMM! Nuclear winter.

 

[Integral]

Originally posted by ObsessiveMathsFreak
When Ben Franklin first labeled charges as positive and negative, whatever way he went about it, he gave electrons negative charge and protons positive charge. Of course he didn't know about electrons and protons at the time, just the charges caused by an excess and shortage of electrons, which he didn't know about.

Anyway, having labeled his charges + and - he just then said, ok, charge flows from + to - . Unfortunate as we now know that it is only the electrons that flow any they carry their - charge to + areas. However at the time no one could find any difference at all between + and - charges.

The reason we still use the idea that current flows from + to - is because transistors are easier to understand, if viewed in this way.
Among other things. Of course if w tried to change it now, half of the world would use the old system and half the new and sooner or later ... BOOOOMMMM! Nuclear winter.

Got news for you, a good part of the world is already being taught negative current flow and has been for the past 30 or 40 years. Transistors work just fine, in fact everything works fine. It is, in fact simpler and makes more sense to track the actual current carriers.

 

[zoobyshoe]

Every book I've ever read said that charge flows from negative to positive, negative being where the excess of electrons is and positive being where the deficit of electrons is.

Am I hearing people say this is not universally taught this way?

 

[Integral]

Shhh...

American engineers do not realize that the current carrires are negitive, they learn positive current flow. Why? Cus' they seem to think it makes more sense?

Don't confuse 'm

 

[wbeaty]

There's a BIG problem here, and it's not with the folks who think that electric current is positive particles.

Misconception: during electric currents, it is the electrons that flow.

Why is this a misconception? Because electric current in electrolytes and in plasmas is NOT NOT NOT a flow of electrons. Stick some wires in salt water and you get positively charged sodium atoms flowing one way, and negatively charged chlorine atoms flowing the other. No bare electrons are allowed in water. Zap yourself on a high-volt battery, and the positives flow one way through your flesh while the negatives simultaneously flow the other way. Which one is the current? Both are. You have to add them together... but first you have to reverse one of them, since positive charges flowing leftwards do the same thing as negative charges flowing right.

Yes, electric current is flowing electrons... WHEN THAT CURRENT TAKES PLACE IN METALS. But there are lots of other conductors besides metal. There are batteries and sparks and fluorescent tubes and living tissues and electroplating baths and fuel cells and ground currents and aurora/solar-wind.

There are also specialized conductors where the movable charges are the positive hydrogen ions. In other words, PROTONS. These are used in modern fuel cells, but also appear in the everyday world: solid ice is a poor insulator because it's a proton conductor. Go search google for "proton conductor" and I bet you get many thousands of hits.

Anyone who mistakenly believes that electric current "is" a flow of electrons will have no trouble with metal wires and vacuum tubes. This whole "negative current misconception" was apparently born during the vacuum-tube era and spread by military handbooks for technicians who only had to handle wires and vacuum tubes. But the people taught from these books will have terrible troubles in trying to figure out how batteries work (for example, many of them falsely believe that there is no current in a battery electrolyte; that batteries form an open circuit.) The same people will also feel very uncomfortable when trying to understand how diodes work (to say nothing of transistors.) Those backwards moving vacancies in the p-doped semiconductors are nearly a violation of their "religion." Just don't tell them about proton conductors. It tends to trigger fundamentalist flamewars.

To understand batteries, fuel cells, sparks & plasma, p-dope silicon, etc., you have to adopt the physicists' viewpoint. You have to convince yourself that electric current can be a flow of negatives in one direction, *OR* a flow of positives in the other direction, *OR* a flow of negatives and positives in both directions at the same time. It all depends on the type of conductor in which the current appears.

See:

WHICH WAY DOES 'ELECTRICITY' REALLY FLOW?
http://amasci.com/amateur/elecdir.html

and also:

BEN FRANKLIN WAS RIGHT AFTER ALL
http://amasci.com/miscon/eleca.html#frkel


(((((((((((( * )))))))))))))))
Bill Beaty http://amasci.com
Science Hobbyist
billb@eskimo.com

 

[Integral]

hummm...

You say

Misconception: during electric currents, it is the electrons that flow.

Then you say

You have to convince yourself that electric current can be a flow of negatives in one direction, *OR* a flow of positives in the other direction, *OR* a flow of negatives and positives in both directions at the same time.

Doesn't the last kind'a contradict the first?

Pehaps you should moderate that inital statement.

 

[wbeaty]

Originally posted by Integral
hummm...

Doesn't the last kind'a contradict the first?

Pehaps you should moderate that inital statement.

OK. Electric currents are NOT flows of electrons. They are flows of electrons OR they are flows of electrons and positive ions OR they are flows of just protons OR they are flows of positive and negative ions. It depends on the type of conductor involved.

People who believe that electric currents "are" flows of electron will get lost if they try to understand the parts of physics and electronics where electric currents are flows of something besides pure electrons.

 

[wbeaty]

Just musing here...

If a student was convinced that all electric currents were flows
of negatively charged particles, what would happen? That
knowledge is useful. It allows us to visualize how wires
and resistors and coils and vacuum tubes work.

But if that student started to study transistors, he or she would
be stopped dead. The student wouldn't even grasp diodes. They'd
get to the part about hole flow in p-type conductors and get
stuck. To understand semiconductor devices, you MUST accept that
the current in some conductors is a flow of positive particles.
No messing around! No pretending that holes are "really" just
electrons moving backwards.

(Also try working backwards... if you don't understand the
insides of transistors, and don't even have a good hold of how
diodes work, could it be that you never really accepted that
positive charges really are flowing through the p-type
semiconductor?)


And the "negative current" religion doesn't only keep students
from attaining a solid grasp of diodes and transistors. Electric
currents in electrolytes are also non-negative charge flows.
If you were taught that electric current "is" electron flow,
then you'll be blocked from ever really understanding batteries,
or electroplating, or pulses in human nerves.

The above stuff I'm saying from experience. I graduated engineering
school and was working for many years before I started re-teaching
myself simple electricity from the positive/negative current
viewpoint. Until I re-learned the simple stuff, I had no idea
how easy it was to understand batteries, transistors, etc. Also,
I had no idea how BADLY I understood these things until the fog
started clearing from my mind. My belief in negative-particle
electric currents was an immense mental block for me. Yet most
other people have the same block... and if you live in a world
where everyone has the same disease as you do, you assume that
such conditions are just normal life, and have no reason to suspect
that great improvements could be made.

 

[wbeaty]

having to publish two books...

Heh. Just by coincidence I stumbled across these two:


Introductory Electronic Devices and Circuits: Conventional Flow Version, R. Paynter




Introductory Electronic Devices and Circuits: Electron Flow Version, R. Paynter



Heh. To be consistent, he should publish a third and fourth book, "ion flow version" where all the conductors contain equal numbers of opposite charges which flow in both directions at once... and "plasma current version" where the circuits all contain free electrons flowing fast in one direction, and heavy positive gas ions flowing much slower in the opposite direction.

And what about the particle beam version, where the electrons in conductors actually do flow at nearly the speed of light, rather than flowing extremely slowly as they do in metal wires.

 

[Integral]

Originally posted by wbeaty
Just musing here...

If a student was convinced that all electric currents were flows
of negatively charged particles, what would happen? That
knowledge is useful. It allows us to visualize how wires
and resistors and coils and vacuum tubes work.

But if that student started to study transistors, he or she would
be stopped dead.The student wouldn't even grasp diodes. They'd
get to the part about hole flow in p-type conductors and get
stuck.

This is utter nonsence. I do not recall a single person "being stuck" on hole flow.
You really need to learn some moderation. This is really not as difficult as you make it out to be. I was taught in the Navy ET A school and we were made VERY aware that it could be viewed from either way, postitive or negitive. We were also taught that any charged particle could be a current carrier if it was mobile. Why are you so aggressive about this stuff?

To understand semiconductor devices, you MUST accept that
the current in some conductors is a flow of positive particles.

Once again you are spouting nonsence. Holes are NOT PARTICLES. No There is not doubt about this, an absence of an electron does NOT constitue a particle.

No messing around! No pretending that holes are "really" just
electrons moving backwards.

Interesting concept. I never heard it but that way, it was presented to us as an absence of an electron, which move the other way.

(Also try working backwards... if you don't understand the
insides of transistors, and don't even have a good hold of how
diodes work, could it be that you never really accepted that
positive charges really are flowing through the p-type
semiconductor?)


And the "negative current" religion

Seems to me that you are the only one preaching anything.

Chill out

doesn't only keep students
from attaining a solid grasp of diodes and transistors. Electric
currents in electrolytes are also non-negative charge flows.

Once again this is pretty much nonsence I do not know of anyone that is taught this stuff as a religion, we were taught principles, most of which stood well for me even thorugh a BS in Physics.

If you were taught that electric current "is" electron flow,
then you'll be blocked from ever really understanding batteries,
or electroplating, or pulses in human nerves.

Any one who is taugth basic priciples has no trouble with such things. I think you are full of it.

The above stuff I'm saying from experience. I graduated engineering
school

Ahh... an electrical engineer.. That explains a lot. Needless to say I do not have high regrad for many of the EE I have worked with through the years.

and was working for many years before I started re-teaching
myself simple electricity from the positive/negative current
viewpoint. Until I re-learned the simple stuff, I had no idea
how easy it was to understand batteries, transistors, etc. Also,
I had no idea how BADLY I understood these things until the fog
started clearing from my mind. My belief in negative-particle
electric currents was an immense mental block for me. Yet most
other people have the same block...

this is a huge assumption on your part.

and if you live in a world
where everyone has the same disease as you do, you assume that
such conditions are just normal life, and have no reason to suspect
that great improvements could be made.

This last may be your problem. I have to stop an think about which current carrier is being used but in general it does not bother me to move from one to the other.

 

[Jimmy]

..But if that student started to study transistors, he or she would be stopped dead. The student wouldn't even grasp diodes. They'd
get to the part about hole flow in p-type conductors and get
stuck. To understand semiconductor devices, you MUST accept that
the current in some conductors is a flow of positive particles.
No messing around! No pretending that holes are "really" just
electrons moving backwards.

I had six months of Army schooling dealing with digital communications and also acquired an associates degree in Electronics from a two year program. During both schools, we were well made aware of both positive and negative current flows. We were taught that electrons were not the only charge carriers. During both my military and civilian training dealing with semi-conductor physics, we learned about both hole and electron flow. We did, however deal with mainly the negative current carriers. I never had any conceptual blocks when it came to semiconductor devices.

When considering P-type materials, the vacancies in the valence shell of the atoms are certainly positive in potential. However, positive current is not the only thing which exists in P-type materials. The flow of vacancies (if they can really be said to flow) depend on the electrons which move to occupy those vacancies. Of course, the electrons need the vacancies in order to move just as the vacancies need the electrons.

Certainly you can treat vacancies as positive potentials which move in the opposite direction of the electrons. However, I find it difficult to accept holes as real particles. I never heard of them referred to as backward moving electrons.

 

[McQueen]

Yes, electric current is flowing electrons... WHEN THAT CURRENT TAKES PLACE IN METALS. But there are lots of other conductors besides metal.
Mr Beatty
I have visited your site and was greatly impressed by your open minded approach and undoubted expertise in the field. . However I would like to point out that you have often said , in numerous instances , that the actual energy in an electrical current is present in the field surrounding the conductor. How do you rationalise that statement with your recent posts.

 

[wbeaty]

Originally posted by McQueen
However I would like to point out that you have often said , in numerous instances , that the actual energy in an electrical current is present in the field surrounding the conductor. How do you rationalise that statement with your recent posts.

Hi McQueen! You'll have to explain further, I don't see the problem that you do.

Energy flow in circuits has little to do with the polarity of the charges flowing in circuits. Analogy: energy flow in sound waves has little to do with the detailed chemical properties of the medium through which the sound travels, and sound waves can travel through all sorts of materials.

Energy flow in AC/DC circuits follows the same rules as 2-wire RF transmission lines. When "wattage" propagates across a DC circuit, it's only able to follow the wires because motions of charges in the wires (current) creates a magnetic field and because imbalance of charges (voltage) creates an electric field. The polarity of the charged particles doesn't matter, since the same magnetic field can appear when positive charges move leftwards or when negative charges move right. The same is true of the electric fields. Or in other words, we'll find the same voltage and current in our electric transmission lines whether they're made of copper, or made of hoses full of salt water, or made of glass tubes full of glowing neon.

Here's a less relevant analogy: if we send mechanical energy from place to place through a system of belts and pulleys, the mechanical energy travels as sound waves in the belts, while the material in the belts moves very slowly. If we send electrical energy from place to place through a system of wires, the electrical energy travels as EM waves along the wires, while the charges inside the wires move very slowly.

 

[wbeaty]

Originally posted by mmwave
Holes are conceptualized as though they are positive particles carrying charge for two reasons. One is that they have an effective mass in moving though the lattice that is heavier than that of the conduction band electrons (holes have lower mobility than electrons). The second is that there are fewer holes to keep track of then there are electrons in the valence band so it's cleaner to keep track of where there is a missing electron.

Yep. And other important reasons exist: a hole can have a trajectory just like a genuine material particles, and holes follow a conservation rule (a hole is not like a pattern of charge; it can't spread out as a diffuse cloud, or appear or vanish for no reason.)

It's not difficult to understand diode/transistor physics once we freely adopt a conceptual model where holes have all of the characteristics of a real subatomic particle. But if a student refuses to accept this, and instead insists that holes are some sort of abstract pattern of charges which is hard to visualize, that student will learn this stuff much more slowly or perhaps not at all.

BIG QUESTION: In circuit physics, which characteristics of holes are *not* the characteristics of electrons and ions? The major difference: electrons/ions can depart from the conductors which form the electric circuit, while holes cannot.

 

[russ_watters]

Originally posted by mmwave
Did you learn electronics in tech school or at the naval academy?

I'm curious because all the engineers I have ever met learned positive current flow but all the electronic technicians learn electron flow. I think it's a conspiracy to keep the technicians from being able to learn from the engineering books. Sort of a protect yourself from unauthorized competition guild thing. I bet the engineers at the naval academy learn positive current flow too.

I just so happened to take an intro EE course at the Naval Academy and we learned negative to positive.

 

[wbeaty]

Originally posted by Jimmy
During both schools, we were well made aware of both positive and negative current flows. We were taught that electrons were not the only charge carriers.

If everyone had such a good experience, most of these weird conceptual problems wouldn't exist.

For example, there would be no controversy about current in circuits "really" being negative. Everyone would realize that charge-flow REALLY IS pos or neg depending on which component it happens to be inside at the moment. The need for a simplifying assumption would then become obvious: ignore the actual particles, and declare all particles to have the same polarity, the polarity of "Amperes." In rare situations where we must visualize the actions of the moving charges, we would happily accept reality, and not try to pretend that they are all "really" negative charges.

One thing to note: even the folks who have been trained in terms of negative current might use this concept only rarely in day to day electronics work. Instead they assume a "double negative" and then use positive currents like the engineers do. Also, note that all ammeters inherently perform a "double negative" and measure positive currents. The meter says +2.5A, you write that down. You *don't* use special "negative current religion" ammeters which have backwards polarity displays, write down "-2.5A electron current," then write -(-2.5A), then cancel the negatives and finally write +2.5A.

 

[wbeaty]

Completely off topic post removed

Wbeaty,
I responded to your post in kind. If you do not like flames then moderate you tone.

Integral

 

[Jimmy]

wbeaty: One thing to note: even the folks who have been trained in terms of negative current might use this concept only rarely in day to day electronics work. Instead they assume a "double negative" and then use positive currents like the engineers do. Also, note that all ammeters inherently perform a "double negative" and measure positive currents. The meter says +2.5A, you write that down. You *don't* use special "negative current religion" ammeters which have backwards polarity displays, write down "-2.5A electron current," then write -(-2.5A), then cancel the negatives and finally write +2.5A.

We spent about a week or so studying basic semiconductor physics, but outside of that, we didn't really concern ourselves with hole current. Since hole flow is only happening inside the semiconductor device. We were aware in a limited fashion what was going on inside a diode but naturally spent more time studying the practical uses of a diode; ie, rectifiers, clippers, regulators, etc. From there, we really only looked at electron flow outside of the device itself.

It's been about 12 years since I've been in school and I haven't thought about this stuff for awhile. To be honest, I was sometimes a little bored with being a technician and always wanted to understand things at a more fundamental level. It wet my appetite for physics. Actually that and amateur astronomy really peaked my interest in physics. I've studied quite a bit on my own but that has remained just a hobby for me. Eventually I'll take some classes I reckon.

 

[chroot]

1) Holes are not real particles. You cannot have a hole in isolation sitting in a containment vessel. Holes are the absence of electrons.

2) There are no actual positively charged particles moving in a p-type semiconductor. No ions, no subatomic particles, no protons. P-type semiconductors have only one type of real mobile charge carrier: electrons.

3) That holes can behave like particles is indisputable. They can be assigned mobilities, they can be be described quite nicely as positive "particles" in a model of semiconductor behavior. This is a simple result of the way Nature works: many things are symmetrical. Note that the existence of a model describing the hole as a positive particle does not mean the hole is really a positive particle at all. It's a high-level model.

4) wbeaty, your argument is largely semantic. In the context of semiconductor physics, you may as well regard the hole as a particle, on the same footing as the electron, since the model works quite well that way. In particle physics however, such convention would be heresy. Choose your models wisely for the task at hand.

- Warren

 

[krab]

Hey Beaty, take a pill. This wasn't a flame war till you showed up with all your boldface and uppercase type.

Anyway, I have no hot clue why this is a controversy. Any physics student knows that negative charges moving to the right constitute the same current as positive ones to the left. No one I know was "stopped in their tracks" by switching the charge carrier sign. Maybe it's a problem for EE students. I recall a time when I was in elementary school when the concept of two negatives being a positive was not transparent, so maybe I'm too far removed to be sympathetic.

 

[lethe]

Originally posted by chroot
In particle physics however, such convention would be heresy.

heresy? someone better tell that to Dirac, who first proposed the interpretation of antiparticles as holes in the "Dirac sea"

 

[Integral]

Originally posted by russ_watters
I just so happened to take an intro EE course at the Naval Academy and we learned negative to positive.

I was trained at ETA school Great Lakes Ill. (first)
Then learned E&M inroute to a BS in Physics.

 

[Integral]

Originally posted by wbeaty

The above stuff I'm saying from experience. I graduated engineering
school and was working for many years before I started re-teaching
myself simple electricity from the positive/negative current
viewpoint. Until I re-learned the simple stuff, I had no idea
how easy it was to understand batteries, transistors, etc.

You confuse me with this post, the way I read it, you did not understand electronic/electricity until you learned NEGATIVE current flow. Am I correct in assuming that your initial education was postitive which must not have made much sense, then finally when you considered negative flow it clicked.

This is of course makes good sense because as far a circuits go if you follow the electrons you are actually considering the fundamental physics of the situation. The concept of holes in semiconductors is also very physical. So there is no doubt in my mind that that electron current is the best way to teach this subject. You seem to confirm that.

What are you arguing about? I have asked you to moderate your tone twice, here is a third time. Calm down. Are you capable of discussing these matters without the inflammatory attitude?