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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 kilowatt hour (kWh); 1000 kWh=1 megawatt hour (MWh); 1000 MWh = 1 gigawatt hour (GWH), 1000 GWH = 1 terawatt hour (TWh).

 

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Travel

Bali

 

 

 

 

 

At the end of February 2016 Wendy and I took a package deal to visit Bali.  These days almost everyone knows that Bali is a smallish island off the east tip of Java in the Southern Indonesian archipelago, just south of the equator.  Longitudinally it's just to the west of Perth, not a huge distance from Darwin.  The whole Island chain is highly actively volcanic with regular eruptions that quite frequently disrupt air traffic. Bali is well watered, volcanic, fertile and very warm year round, with seasons defined by the amount of rain.

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Fiction, Recollections & News

Easter

 

 

 

Easter /'eestuh/. noun

  1. an annual Christian festival in commemoration of the resurrection of Jesus Christ, observed on the first Sunday after the full moon that occurs on or next after 21 March (the vernal equinox)

[Middle English ester, Old English eastre, originally, name of goddess; distantly related to Latin aurora dawn, Greek eos; related to east]

Macquarie Dictionary

 


I'm not very good with anniversaries so Easter might take me by surprise, were it not for the Moon - waxing gibbous last night.  Easter inconveniently moves about with the Moon, unlike Christmas.  And like Christmas, retailers give us plenty of advanced warning. For many weeks the chocolate bilbies have been back in the supermarket - along with the more traditional eggs and rabbits. 

Read more: Easter

Opinions and Philosophy

The demise of books and newspapers

 

 

Most commentators expect that traditional print media will be replaced in the very near future by electronic devices similar to the Kindle, pads and phones.  Some believe, as a consequence, that the very utility of traditional books and media will change irrevocably as our ability to appreciate them changes.  At least one of them is profoundly unsettled by this prospect; that he argues is already under way. 

Read more: The demise of books and newspapers

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