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Created and maintained by Bill Beaty. Mail me at:
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WHICH WAY DOES THE
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Because the negative particles carry a name that sounds like
"electricity," some beginners unfortunately start thinking that the
electrons ARE the electricity, and they wrongly start imagining that the
protons
(having a much less electrical name?) are not electrical. A few text and
reference books even outright state this, saying that electricity is
composed of electrons. Nope, wrong. In reality the electrons and protons
carry electric charges of equal strength. If electrons are
"electricity", then protons are "electricity" too. Now everyone will rightly tell me that the protons within wires cannot
flow, while the electrons can. Yes, this is true... but only true for
metals. And it's only true for solid metals. And only true for
solid
metals which are not moving. All metals are composed of
positively charged atoms immersed in a sea of movable electrons. When an
electric current is created within a solid, non-moving copper wire, the
"electron sea"
moves forward, but the protons within the positive atoms of copper do not.
However, solid metals are not the only conductors, and in many
other substances the positive atoms *do* move, and they *do* participate
in the electric current. These various conductors are nothing exotic.
They are very common, they all around us; as close to us as they can
possibly be.
Non-electron Charge-flowFor example, if you were to poke your fingers into the back of an old-style television set, you would suffer a dangerous or lethal electric shock. During your painful experience there obviously was a considerable current directed through your body. However, no electrons flowed through your body at all. The electric charges in a human body are entirely composed of positive and negative charged atoms or "ions." During your electrocution, it was these charged atoms which flowed along as an electric current. The current in your flesh was a flow of positive sodium and potassium atoms, negative chlorine, and numerous other more complex positive and negative molecules. During the electric current, the positive atoms flowed in one direction, while the negative atoms simultaneously flowed in the other. Imagine the flows as being like crowds of of tiny moving dots, with half the dots going in one direction and half in the other. The populations of little dots move through each other without any dots colliding. The postive atoms behave like flowing protons, but protons with entire atoms attached. The negative atoms behave like electrons which are dragging an entire atom along with them. Some of the flows are -OH negative water ions, and some of the flows are actual protons (although we usually call these +H positive hydrogen ions.) So, inside human flesh ...which direction did the electric
current REALLY go? Do we follow the negative particles and ignore the
positive ones? Or vice versa, following the positives? There is a simple
answer, but first... Batteries are another example of non-electron or "ionic" conductors.
Whenever you connect a lightbulb to a battery, you form a complete
circuit, and the path of the flowing charge is through the inside
of the battery, as well as through the light bulb filament and the
connecting wires. Battery electrolyte is very conductive. Down inside
the battery, within the wet chemicals between the two plates, the amperes
of flashlight current appears as a flow of both positive and negative
atoms. There is a powerful flow of electric charge going through the
battery, yet no individual electrons flow through the battery at all.
So, during the time when the charges flow between the two plates of the
battery, what's the real direction? Not right to left, not left to
right, but in both directions at once. About half of the charge-flow is
composed of positive atoms, and the remaining portion is composed of
negative atoms flowing backwards. Of course in (solid, unmoving) metal
wires outside the
battery, the real particle flow is only from negative to positive. But
inside the battery's wet electrolyte, the charge-flow goes in two opposite
directions at the same time. (And if we should build a circuit entirely
out of hoses full of salt water, with no metal conductors used, then
all the current would be bi-directional.)
Two-way currents are commonThere are many other places where these kinds of positive/negative charge flows can be found. In the following list of devices and materials, the electric charges found within the conductors are a combination of movable positive and negative particles. During an electric current, both varieties of particles are flowing past each other in opposite directions.TWO-WAY POS/NEG ELECTRIC CURRENTS CAN EXIST IN:
This list is not so short. Again I ask you, what is the REAL direction of
electric currents? We cannot solve the problem by belittling it, or by
pretending that two-way currents pertain only to something exotic, or
pretend that it's all completely separate from everyday life. Our own
nervous system is based on the two-way currents. We dare not think that a
current in a metal wire is "real," while currents in human flesh somehow
are not.
Well, what is "current?"To gain some insight, let's examine the details. While trying to understand electric circuits and electrical measurements, we need a simple way to take measurements of this important entity named "Electric Current." But to measure currents, won't we first need to measure how much of the current is composed of negative particles going one way, and of positive particles the other? Yes, but we only need this information if we want to know everything about the electric current. The flowing negatives and positives are usually not equal, and the speed of the positives in one direction is usually not the same as the speed of the negatives in the other. Electric current can be complicated!
However, there is a cute trick we can pull in order to avoid having to
look at the particles at all. And that trick holds the answer to the
question. Electric currents produce three main effects: magnetism, heating, and
the voltage drop across resistive conductors. These three effects cover
almost everything we encounter in electronics. And these three effects
don't care about the amounts of positive and negative particles, or
about their speed, their mass, their charge, etc. If a hundred positive
particles flow to the left per second, this gives exactly as much
magnetism, heating, and voltage as a hundred negative particles flowing to
the right per second. (Note: this is because reversing the polarity of
the particles reverses the current, and reversing the particle direction
reverses the current again! Two negatives make a positive.) Magnetism,
heating, and voltage drop together represent nearly every feature that's
important in everyday electrical circuitry. Therefore, as far as most
electrical devices and circuits are concerned, it makes no difference if
the current is made of positive particles going one way, or negative
particles going the other... or half as many negatives flowing backwards
through a crowd of half as many positives.
Put simply, your ammeter doesn't care about the direction or
speed of the flowing particles. It cannot measure these, or even detect
them. The definition of "Ampere"
doesn't acknowledge the speed of the particles, or their
direction, or their number. So, in order to simplify our measurements and our mental picture of
Electric Currents, we cut away the unused parts of the picture. We look
at Amperes, not at flowing particles. We
make the negative particles positive, then add their current to any positive
particles which were flowing forward. We ignore their speed, and instead
measure only the flow rate: the total charge flowing per second. We
stop thinking of current as being a flow of real physical particles.
Instead we intentionally define "electric current" as being a flow
of exclusively positive particles flowing in one particular direction.
We don't care about the real polarity of the particles. We don't care
about their speed, and we don't care about their number. We ignore both
the chemical effects and the effects of the velocity and direction of
moving particles. We ignore the collisions between positive and negative
particles. All we care about is the total net charge which moves past a
particular point in the circuit. The real charges are too complicated to
deal with. We don't care if any currents inside your body are made of
half-positive, half negative particles flowing in opposite directions!
The added complexity gets us very little information
as long as we're only interested in voltage drop, magnetic fields, and
heating.
Particle-flow is real, "Amperes" and "current" is notOnce we start ignoring the speed and direction of the charges, then we can easily build electrical instruments or "amp meters" which measure the Conventional Electric Current in terms of the magnetism which the charge-flow creates... or by the voltage drop which appears across a resistor, or by the temperature rise being created in a calibrated piece of resistance wire. These three types of meter will agree that a "current" is a "current" regardless of the particle polarities and flows. Then we can use these meters everywhere. In nearly every situation they will tell us all we could ever want to know about flows of charged particles in any circuit. An amp-meter might not be appropriate when used in an exotic physics experiment. It won't paint the correct picture when designing electron beams inside vacuum tubes, or ion flows in nerve fibers. It cannot detect real current; instead it only measures our conventionally-defined simple current. But for more than 99% of electricity and electronics, the direction of the particles is irrelevant, and an ammeter tells us the so-called "real" current while hiding the true particle flows.
Or to put it simply: we pretend that "electric currents" are always
composed of POSITIVE particles of unknown speed, so that any negative
currents are defined
as positive particles flowing backwards rather than negative particles
flowing forwards.
Confusing students for two hundred yearsWe do cause some problems by choosing a positive charge convention. For example, what happens if we all spend many years thinking in terms of such simplified "electric current?" Might we eventually start believing that this oversimplified concept of positive electric current is REAL? Yet it's not real, it's simply one way to simplify things. There's a genuine difference between the simplified picture versus the actual particle flows. The Amps inside salt water and metals would not quite match a visual picture of moving particles. But if we truely believe that the amperes are real, we might start to doubt the existence of flowing charges. We might start to see "Electric Current" itself as a sort of abstract, invisible, difficult-to-imagine thing. We might lose track of the facts that electric current is an actual flow of matter. We might lose track of the fact that there are real, visible particles flowing along inside that circuit, or that these particles have an actual average speed, mass, and direction.
Because "amperes" are so incredibly useful, the simplified interpretation
of Current takes over and becomes more real than reality. It
allows us to understand parts of physical science which otherwise might be
too complicated to imagine. But in letting the positive charges take
over, some nagging questions are left behind, such as "WHICH WAY DOES THE
ELECTRICITY REALLY FLOW?" (grin!)
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