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The electrically literate may find this somewhat simplified article redundant; or possibly amusing. They should check out Wikipedia for any gaps in their knowledge.

But I hope this will help those for whom Wikipedia is a bit too complicated and/or detailed.

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All cartoons from The New Yorker - 1925 to 2004

 

 

Think of water in a hosepipe

 

Electricity is a means of transporting energy from a source, like the wind, to a device you use to exploit that energy, like your electric toothbrush.

The usual way of explaining electricity is to use the simile of the flow of water in a pipe (a current of water).  We are all familiar with a hose pipe.  Its pressure is analogous to the voltage; and the flow of water is analogous to the current. 

 

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The author - almost two - learning about currents and voltage

 

The work that can be done in an hour, for example if you use the jet to spin a bicycle wheel or push leaves along a path, is the pressure (like Volts) times the current (like Amps) for an hour. 

You won’t be able to squirt the water from your hose far if there is no pressure or if there is no water.  You need both.  If the pressure falls the water ceases to flow.

It’s the same with a stream (current) of electricity making its way down a conductor; for example a wire. The electrical force acting on an electrical current provides the power to do work.

Most quantities in modern physics are named after an early natural philosopher or inventor.  If we had let tradition do it, each would probably be related by some strange number, like the number of feet in a mile; or pounds in a ton.  But most new physical values use the decimal system (the rationalised MKS or SI units: meter, kilogram, second).

A Watt is a measure of Power; the instantaneous capacity to do work; named after James Watt. 

Under this system we define one Watt as equal to one Volt (electrical  force) multiplied by one Ampere (current); or Amp for short.  Read More...

Using this simple relationship you can easily calculate that 1000 Watts of power (one kilowatt) can be carried by a current of 4.17 amps at 240 volts (240 x 4.17 = 1000)

But the same power requires only 0.002 amps at 500,000 volts (0.002 x 500,000 = 1000).  So when you turn on an electric kettle or toaster it will draw around 4 amps in your home at 240V but only 0.002 amps in the very high voltage grid to bring it from the generator in the power station.

Power exerted for a period of time is called Energy.  Physicists measure energy in Joules (1 J= 1Watt acting for 1 second).  But to get to a smaller working number electricity companies like to measure energy in kilowatt hours (1 kWh =  3,600 kJ = a thousand Watts acting for the seconds in one hour) 

When your bill comes, you get charged for the Energy, the number of kWh* you used, not Power (kW).

 

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*Terminology:  1000 Wh = 1 killowatt hour (kWh); 1000 kWh=1 megawatt hour (MWh); 1000 MWh = 1 gigawat hour (GWH), 1000 GWH = 1 terawatt hour (TWh).

 


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Travel

Cuba

 

 

 

What can I say about Cuba? 

In the late ‘70s I lived on the boundary of Paddington in Sydney and walked to and from work in the city.  Between my home and work there was an area of terrace housing in Darlinghurst that had been resumed by the State for the construction of a road tunnel and traffic interchanges.  Squatters had moved into some of the ‘DMR affected’ houses.  Most of these were young people, students, rock bands and radically unemployed alternative culture advocates; hippies. 

Those houses in this socially vibrant area that were not condemned by the road building were rented to people who were happy with these neighbours: artists; writers; musicians; even some younger professionals; and a number were brothels.  

Read more ...

Fiction, Recollections & News

Merry Christmas

 

 

 

2020 is a year we are unlikely to soon forget.  No travel after a very fortuitous cruise to PNG in February and March that we just got in before COVID-19 hit. Last year my German grandchildren were able to visit Australia with Emily their mother. Leander got to improve his English, and he and Tilda, now 3, got to enjoy an Australian beach. Thanks to WhatsApp we can still get together face-to-face and I can report that Tilda also understands English, in addition to her native German. Yet it's not quite like us being there or them being here.

As Tim Minchin sings in White Wine in the Sun [turn on your sound...] Christmas is a time for family.  So the lyrics:

 

And if my baby girl
When you're twenty-one or thirty-one
And Christmas comes around
And you find yourself nine thousand miles from home
You'll know what ever comes
Your brothers and sisters and me and your mum
Will be waiting for you in the sun
When Christmas comes
Your brothers and sisters, your aunts and your uncles
Your grandparents, cousins and me and your mum
We'll be waiting for you in the sun
Drinking white wine in the sun Darling, whenever you come
We'll be waiting for you in the sun
Drinking white wine in the sun
Waiting for you in the sun Darling, when Christmas comes
We'll be waiting for you in the sun
Waiting
  

have a special meaning:  I really like Christmas - It's sentimental, I know.

 

Those of you who read last year's message will find what follows familiar. Apart from acknowledging grandchildren: Billy and Vivienne for assistance in assembling (usefully) and now becoming the sole Christmas Tree decorators I haven't changed a word.

Read more ...

Opinions and Philosophy

Australia's carbon tax

 

 

Well, the Gillard government has done it; they have announced the long awaited price on carbon.  But this time it's not the highly compromised CPRS previously announced by Kevin Rudd.  

Accusations of lying and broken promises aside, the problem of using a tax rather than the earlier proposed cap-and-trade mechanism is devising a means by which the revenue raised will be returned to stimulate investment in new non-carbon based energy. 

Read more ...

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