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What is electricity - really?

 

Above I invited you to think of electricity as a fluid of electricity running through a conductor that acts like a pipe.

According to our present conceptual model electricity is due to the movement of electrons in a conductor. Electrons are negatively charged fermions (particles that make up an atom) that are generally happy to hang around an atom to balance the positive charge of its nucleus.  Read More...

Electrons are envisaged as milling around in the general vicinity but often at a great distance, relative to the size of the nucleus, like planets around the sun.  The outer electrons define the physical size of an atom. Contrary to some pictures you might have seen they do not orbit elliptically like planets but occupy a space determined by their wave function and energy state.  They are happy bouncing around in this space unless something, like a photon of light or heat, encourages them to jump to another energy level. 

 

 

Conductors and insulators

Some elements, like the metals, bond to each other in such a way that outer electrons can pass energy on to the next; or perhaps get shared in one big cloud. 

By stimulating electrons to move we can make them carry energy along a conductor but this is more like the baton in a relay or an ‘Indian wave’ in a stadium than a flow of water.  Each one in the chain just gives the next one in line a ‘shove’; pass it on. The ‘shove’ goes down the conductor and after passing-on the ‘shove’ each electron continues to hang about as before. 

On the other hand, non-metals tend to form molecules in which the electrons are not free to pass energy on.  A material in which no current can flow we call an insulator.  Read More...

Whether an atom is a metal or not depends on the number of protons in the nucleus.  After disregarding the first two (hydrogen and helium), elements can be lined up nicely by their proton count (roughly half their atomic weight) in a table: the first-row pair of 8 then 18 then 32 columns wide; so that every 8th, 18th then 32nd is similar in properties; for example: a noble gas, a halogen or an alkali.  

This pattern was observed by chemists before it was explained.  Once recognised it allowed chemists to see the gaps and find the missing elements.  This regular pattern of repetition is called the periodic table of the elements. 

 

Periodic table

 

Quantum mechanics now provides a model predicting/describing/explaining this observed behaviour. 

Metals (the salmon-coloured elements above) are not the only conductors.  Some non-metals like carbon have one form, graphite, which is a good conductor and another, diamond, which is a good insulator. 

Selenium, another non-metal, has semiconducting properties and was widely used before silicone in solid state rectifiers.  As a schoolboy I built several battery chargers and power supplies employing  selenium rectifiers which were then easily obtained from disposals stores.  

Black phosphorous is another non-metallic conductor.

If an electron is stripped from and atom (or it acquires extra electron) it is said to be ionised and if the whole atom is mobile; for example: in a fluid (gas or liquid) the whole atom can act as a transport for electrons or of positive charge (an excess of protons). 

For example, salt water is a good conductor and even the earth (rocks and soil) can be used as the return conductor in a circuit. 

As kids we used this in our one-wire telephone to friends in neighbouring houses.

 

 

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Travel

Bridge over the River Kwai

 

 

In 1957-58 the film ‘The Bridge on the River Kwai‘ was ground breaking.  It was remarkable for being mainly shot on location (in Ceylon not Thailand) rather than in a studio and for involving the construction and demolition of a real, fully functioning rail bridge.   It's still regarded by many as one of the finest movies ever made. 

One of the things a tourist to Bangkok is encouraged to do is to take a day trip to the actual bridge.

Read more: Bridge over the River Kwai

Fiction, Recollections & News

Dan Brown's 'Origin'

 

 

 

 

 

The other day I found myself killing time in Chatswood waiting for my car to be serviced. A long stay in a coffee shop seemed a good option but I would need something to read - not too heavy. In a bookshop I found the latest Dan Brown: Origin. Dan might not be le Carré but like Lee Child and Clive Cussler he's a fast and easy read.

Read more: Dan Brown's 'Origin'

Opinions and Philosophy

Frederick Sanger - a life well spent

 

I have reached a point in my life when the death of a valued colleague seems to be a monthly occurrence.  I remember my parents saying the same thing. 

We go thought phases.  First it is the arrival of adulthood when all one's friends are reaching 21 or 18, as the case may be.  Then they are all getting married.  Then the babies arrive.  Then it is our children's turn and we see them entering the same cycle.  And now the Grim Reaper appears regularly. 

As I have repeatedly affirmed elsewhere on this website, each of us has a profound impact on the future.  Often without our awareness or deliberate choice, we are by commission or omission, continuously taking actions that change our life's path and therefore the lives of others.  Thus our every decision has an impact on the very existence of those yet to be born. 

Read more: Frederick Sanger - a life well spent

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