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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 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

Southern France

Touring in the South of France

September 2014

 

Lyon

Off the plane we are welcomed by a warm Autumn day in the south of France.  Fragrant and green.

Lyon is the first step on our short stay in Southern France, touring in leisurely hops by car, down the Rhône valley from Lyon to Avignon and then to Aix and Nice with various stops along the way.

Months earlier I’d booked a car from Lyon Airport to be dropped off at Nice Airport.  I’d tried booking town centre to town centre but there was nothing available.

This meant I got to drive an unfamiliar car, with no gearstick or ignition switch and various other novel idiosyncrasies, ‘straight off the plane’.  But I managed to work it out and we got to see the countryside between the airport and the city and quite a bit of the outer suburbs at our own pace.  Fortunately we had ‘Madam Butterfly’ with us (more of her later) else we could never have reached our hotel through the maze of one way streets.

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Fiction, Recollections & News

Les Misérables - The Musical

 

The musical Les Misérables has returned to Sydney.   By now we have both seen several versions.    

But we agreed that this new version is exceptional, with several quite spectacular staging innovations and an excellent cast of singers with perhaps one exception who was nevertheless very good.

Despite an audience that was obviously very familiar with the material (if I'm to judge by the not so sotto voce anticipatory comments from the woman next to us) the production managed to evoke the required tears and laughter in the appropriate places.  The packed theatre was clearly delighted and, opera style, the audience shouted approval at and applauded several of the vocal performances, some were moved to a standing ovation at the end.

 

 

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Opinions and Philosophy

Bertrand Russell

 

 

Bertrand Russell (Bertrand Arthur William Russell, 3rd Earl Russell, OM, FRS (18 May 1872 – 2 February 1970)) has been a major influence on my life.  I asked for and was given a copy of his collected Basic Writings of Bertrand Russell for my 21st birthday and although I never agreed entirely with every one of his opinions I have always respected them.

 

In 1950 Russell won the Nobel Prize in literature but remained a controversial figure.  He was responsible for the Russell–Einstein Manifesto in 1955. The signatories included Albert Einstein, just before his death, and ten other eminent intellectuals and scientists. They warned of the dangers of nuclear weapons and called on governments to find alternative ways of resolving conflict.   Russell went on to become the first president of the campaign for nuclear disarmament (CND) and subsequently organised opposition to the Vietnam War. He could be seen in 50's news-reels at the head of CND demonstrations with his long divorced second wife Dora, for which he was jailed again at the age of 89.   The logo originally designed for the CND, the phallic Mercedes, became widely used as a universal peace symbol in the 60s and 70s, particularly in hippie communes and crudely painted on VW camper-vans.

 

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