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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

India and Nepal

 

 

Introduction

 

In October 2012 we travelled to Nepal and South India. We had been to North India a couple of years ago and wanted to see more of this fascinating country; that will be the most populous country in the World within the next two decades. 

In many ways India is like a federation of several countries; so different is one region from another. For my commentary on our trip to Northern India in 2009 Read here...

For that matter Nepal could well be part of India as it differs less from some regions of India than do some actual regions of India. 

These regional differences range from climate and ethnicity to economic wellbeing and religious practice. Although poverty, resulting from inadequate education and over-population is commonplace throughout the sub-continent, it is much worse in some regions than in others.

Read more ...

Fiction, Recollections & News

Reminiscing about the 50’s

 

 

Elsewhere on this site, in the article Cars, Radios, TV and other Pastimes,   I've talked about aspects of my childhood in semi-rural Thornleigh on the outskirts of Sydney, Australia. I've mentioned various aspects of school and things we did as kids.

A great many things have changed.  I’ve already described how the population grew exponentially. Motor vehicles finally replaced the horse in everyday life.  We moved from imperial measurements and currency to decimal currency and metric measures.  The nation gained its self-confidence particularly in the arts and culture.  I’ve talked about the later war in Vietnam and Australia embracing of Asia in place of Europe.

Here are some more reminiscences about that world that has gone forever.

Read more ...

Opinions and Philosophy

A Dismal Science

 

 

Thomas Carlyle coined this epithet in 1839 while criticising  Malthus, who warned of what subsequently happened, exploding population.

According to Carlyle his economic theories: "are indeed sufficiently mournful. Dreary, stolid, dismal, without hope for this world or the next" and in 1894 he described economics as: 'quite abject and distressing... dismal science... led by the sacred cause of Black Emancipation.'  The label has stuck ever since.

This 'dismal' reputation has not been helped by repeated economic recessions and a Great Depression, together with continuously erroneous forecasts and contradictory solutions fuelled by opposing theories.  

This article reviews some of those competing paradigms and their effect on the economic progress of Australia.

Read more ...

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