Atomic Theory

An atom is made up of three sub atomic particles. Protons (positively charged) and Neutrons (No charge) make up the nucleus of an atom. Electrons are negatively charged particles that orbit the nucleus. The protons and electrons give the atom its charge. Positive, negative or neutral.

The electrons exist in up to five shells. The closest to the nucleus can have no more than two electrons. The next shell can carry up to eight. The third can hold up to 18 electrons, 32 in the fourth & finally 50 in the fifth shell. The last shell is called the valence shell and this determines how the atom will interact with other particles.

The atom pictured right has 4 protons 4 neutrons and 4 electrons. It is a Beryllium atom and because it has an incomplete outer shell it is highly reactive with other atoms and is a good conductor of electricity.Most of the insulating materials used in electrical installations are combinations of a few different elements that have joined in such a way that they have combined to become highly resistant to further change. The most common is PVC (Poly Vinyl Chloride) which is a combined form of Carbon, Hydrogen and Chlorine (C2H3Cl) and is used in the manufacture of cable insulation.

Atoms commonly pass and receive electrons in their interactions. What we need to make this a useful effect is to create a coherent flow of electrons we need a conductor that allows free movement of electrons. The most commonly used conductor in electrical circuits is Copper (Cu). Copper is relatively abundant and has a high melting point of 1085°C. Copper has four shells and a total of 29 electrons. This leaves a single outer valence electron that can move freely with the right amount of encouragement (electro motive force). Another feature of copper is its diamagnetic properties that means it is unaffected by the magnetic fields that are created when a current is flowing.

The table below gives a list of conductors and insulators based upon their conductivity and insulating properties.

Conventional Flow & Electron Flow

Direct current as its name suggests travels in one direction only. It was a significant misunderstanding in physics that current flowed from positive to negative. This could easily have been assumed by the nature of a positive meaning you may have an excess that could be shared with a negative to achieve equilibrium. The reality is that electrons are negatively charged and as such are attracted to the opposite charge so the reality is they flow from positive to negative.

When I first discovered this I was more of a computer geek than an electrically minded researcher. This caused me the biggest headache in electrical science. My first thought was if electron flow is in fact the opposite to what we first thought then in the case of a logic circuit where the output is dependant upon a specific input. Technically a question being asked to prescribe a given response. If it works in reverse then the circuit knows the answer before you have asked the question! This really was my Deep thought, 42 moment. (reference to Douglas Adams - The Hitchhikers Guide to the Galaxy)

Experiments were conducted to ascertain what direction current flows. One such experiment was to run miles of cable to lamps atop a mountain range. When the lights wired in series could be seen one lighting up after another to indicate the direction. This was a great physical exercise but a scientific flop. All the observer could see was they all lit at exactly the same time, nearing the speed of light!

In 1898 JJ Thompson discovered the electron and its negative charge was revealed. With that and the advent of semiconducting components we finally had our eureka moment that the proverbial rug had been pulled. One other way of looking at it is you can approach the rug from either direction and it serves the same purpose! This has given rise to two titles for the flow of electricity, Conventional flow & electron flow.

My advice is just accept that electron flow is not the be all and end all in electronics.
The whole circuit is depedant upon the state of every other part of the circuit as can be demonstrated using ohm's law, power law and kirchhoff's laws etc.

Conventional Flow

Positive to negative conventional flow is still used by designers on circuit diagrams to show the intended 'path'. Conventional circuit diagrams read positive at the top left and negative at the far right or bottom left.

Electron Flow

Electron flow describes the true path of electrons as they are negatively charged they are attracted to the opposite positive electrical charge. Electron flow is from negative to positive.