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General Electronics

Which direction does electrical flow go in a wire? The directions the electrons travel or the direction that positive charges seem to travel?
Electrons go one direction while the positive charges seem to go the other. Which is correct?
Douglas Krantz -- Fire Alarm Engineering Technician, Electronic Designer, Electronic Technician, Writer






Which Way does Electricity Flow?

By Douglas Krantz

As an electrons moves to the left, the atom it leaves becomes positively charged and the atom it goes to becomes neutral. The positive charge appears to be moving, but really just comes and goes on each atom; it's the negative charge on the electron that is moving. The negatively charged electrons are drawn to the positive termminal of the battery, but don't move more than one atom at a time. While it is perceived that the positive charge on the atoms of the conductor is moving to the right, it's not moving. Rather, the electron leaving a neutral atom takes its neutralizing negative charge with it and leaves the atom, waiting for an electron to balance out the charges again, positively charged.
The negatively charged electrons are drawn toward the positively charged battery terminal, or the next positively charged atom. The electrons move.

As an electron leaves the atom and is replaced with another electron, each atom changes from a neutral charge to a positive charge and back again. The atoms themselves do not move.

Because the protons in the nucleus of the atom don't move, the protons don't affect the movement of electrical charges or the magnetic fields; because the electrons move, the electrons affect the electrical charges and magnetic fields.


So... In a wire, negatively charged electrons move, and positively charged atoms don't.

Electrical engineers say that, in an electrical circuit, electricity flows one direction: out of the positive terminal of a battery and back into the negative terminal. Electronic technicians say that electricity flows the other direction: out of the negative terminal of a battery and back into the positive terminal.

These two theories seem to be in conflict. Where'd this confusion over the direction of electrical flow come from?

The Discovery of Electrical Flow

Benjamin Franklin started the confusion. He rubbed wool and wax together and noticed what we call static electricity.

At that time, nobody knew about electrons or charges, but trying to explain the observed phenomena, he concluded that something moved from either the wax to the wool, or from the wool to the wax. It looked to him like something moved from the wax to the wool.

He published the discovery.

The Establishment of the Direction of Flow

Around the world scientists and engineers alike added their own ideas to this theory, held discussions on this theory, published their findings using this theory, and formally established that, for electrical current, this was the direction of flow.

In the scientific and engineering world, and in all the literature and books, everyone "knew" that in a circuit, electricity flowed from the positive battery terminal to the negative terminal. This was a well-established concept and any change to that concept would cause mass pandemonium.

But the confusion over electrical flow direction started anyway.

Cathode Rays

In 1869, using high voltage, German Physicist Johann Hittorf noticed a phenomenon of waves or rays emanating from the cathode in a vacuum tube. Later these rays or waves became known as cathode rays.

The idea was to see if the blackening of the interior of the lamp could be prevented with an extra electode inside the incandescent lamp. That part of the experiment never worked.
With the battery this way, when the filament was hot, negatively charged electrons boiling off the filament would migrate to the positively charged plate. If the battery was reversed so the plate was negatively charged, no electrons would travel to the plate.

Edison Effect

Some years later, on hearing about these rays, and while trying to understand and prevent some blackening on the inside of incandescent lamps, Thomas Edison had one of his assistants place an extra electrode inside a lamp.

It was discovered that if a battery, with its positive side connected to the added electrode (plate), and its negative side connected to the filament (cathode), an electrical current would flow. If the battery was connected the other way around, it was also observed that no current would flow.

This current, flowing from the hot filament, through the vacuum, to the electrode, was invisible. No practical purpose could be found for the discovery, but Edison patented this "Edison Effect" anyway.

The Electron

Years later, J.J. Thomson investigated the cathode rays and he figured out about the electron in the atom. He also concluded that the current flow known as the "Edison Effect" was made by electrons traveling through the vacuum.

The Conflict in the Direction of Electrical Flow

We had a conflict. The theories and books all said that in a circuit, electrical current flows out of the positive terminal of a battery, and returns into the negative terminal. These discoveries concluded that, contrary to conventional wisdom, electrons flowed the other direction.

Conventional Current

Attempting to change the books, theories, and especially the minds of all the engineers and scientists around the world would be the cause of mass arguments. It was also assumed that the actual direction didn't really make a real difference, at least as long as everyone stuck to one direction of electrical flow or the other.

Of course, conventional current flow does not work well with vacuum tubes or with the sub-atomic level understanding of magnetism, but it was decided that these problems were less of an issue than trying to change everybody's minds and all the books.

Rather than having engineers and scientists fighting with each other over the direction of current flow, the decision was made that everyone would stay with what has become known as "Conventional Current".

Back to the Present

Nowadays, in general, the electronic technicians use the electron flow as the direction of electrical current, and the engineers use the conventional direction of electrical current.

Whereas the electronic technician is correct about the movement of electrons, with the exception of electrons traveling through vacuum and the sub-atomic effects of magnetism, there's really no harm in the scientists' and engineers' concept of the conventional electrical current as electrical flow.

As a matter of fact, for a few scientific purposes, the direction of conventional current helps in understanding. Lightning, for example, starts at the positively charged ground that draws electrons from air molecules close by. As the positive charge travels up, the electrons from further up are drawn down until the whole column of air is ionized, conducting electrons from the negatively charged clouds to the ground.

Liquid or gaseous substances like air, water, even human flesh, have positive ions (atoms without enough electrons to make them neutral) that physically move. These carry their positive charge with them as they travel through the substance. (This flow is really ion migration, but is considered by some to be electrical flow.)

Acid in batteries and electrolytes in electrolytic capacitors are examples of this. Some people consider this to be the correct direction of electrical flow.

However, in electrical design and maintenance, batteries and capacitors are the exceptions and not the rule. They are only components shown on schematics and wiring diagrams.

There is a lot more to the drawings than just these exceptions. For the understanding of electrical current flow in solid materials like copper (lines on the schematics), and components like semiconductors, most capacitors, resistors, inductors and transformers, etc., the atoms stay in place while the electrons move.

Does It Really Make a Difference?

The negatively charged electrons are drawn to the positive termminal of the battery, but don't move more than one atom at a time. While it is perceived that the positive charge on the atoms of the conductor is moving to the right, it's not moving. Rather, the electron leaving a neutral atom takes its neutralizing negative charge with it and leaves the atom, waiting for an electron to balance out the charges again, positively charged.


Getting back to the diagram though, one has to really understand what is being looked at. Is it the negatively charged electron movement to the left, or is it the passing of positive electrical charge to the right, that is the direction of electrical flow?

The answer to this is more about what else is being considered. There are two components to electromagnetic force, for example.

Was this
helpful?
Yes   No

Electrical Force -- Because the individual electrons are moving to the left so slowly and the positive charges are being passed on to the right so fast, the electrical flow would be considered to be electrical charges being passed to the right.

Magnetic Force -- Then again, because the positive charges aren't physically moving, and magnetism is tied in with electron or proton movement (in a wire, it's the electron movement that is creating the magnetism), the electrical flow would be considered to be electrons moving to the left.

Arrows

Of course, because engineers thinking in terms conventional current flow are the ones getting to make the electronic symbols we see on schematics, the arrows point in the direction of conventional current flow and not in the direction of electron flow.

The electronic technicians understand this and live with these symbols.





References:

http://www.mi.mun.ca/users/cchaulk/eltk1100/ivse/ivse.htm - Conventional Current and Electron Flow

http://www.allaboutcircuits.com/vol_1/chpt_1/7.html - Conventional versus electron flow


http://www.aip.org/history/electron/ - Experiments by J.J. Thomson in 1897 led to the discovery of a fundamental building block of matter



http://history-computer.com/ModernComputer/Basis/diode.html - The Vacuum Tube of John Ambrose Fleming



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


Douglas Krantz

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Electrical Flow


On this website, most references to electrical flow are to the movement of electrons.

Here, electron movement is generally used because it is the electrons that are actually moving. To explain the effects of magnetic forces, the movement of electrons is best.

Conventional current flow, positive charges that appear to be moving in the circuit, will be specified when it is used. The positive electrical forces are not actually moving -- as the electrons are coming and going on an atom, the electrical forces are just loosing or gaining strength. The forces appear to be moving from one atom to the next, but the percieved movement is actually just a result of electron movement. This perceived movement is traveling at a consistent speed, usually around two-thirds the speed of light. To explain the effects of electrostatic forces, the movement of positive charges (conventional current) is best.

See the explanation on which way electricity flows at www.douglaskrantz.com/
ElecElectricalFlow.html
.