*be sceptical - take nothing for granted!
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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

Darwin after Europe

 

 

On our return from Europe we spent a few days in Darwin and its surrounds.  We had a strong sense of re-engagement with Australia and found ourselves saying things like: 'isn't this nice'.

We were also able to catch up with some of our extended family. 

Julia's sister Anneke was there, working on the forthcoming Darwin Festival.  Wendy's cousin Gary and his partner Son live on an off-grid property, collecting their own water and solar electricity, about 120 km out of town. 

We went to the Mindl markets with Anneke and her friend Chris; and drove out to see Gary, in our hire-car, who showed us around Dundee Beach in his more robust vehicle. Son demonstrated her excellent cooking skills.

 

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Fiction, Recollections & News

Skydiving

 

 

On the morning of May1st 2016 I jumped, or rather slid, out of a plane over Wollongong at 14,000 feet.

It was a tandem jump, meaning that I had an instructor strapped to my back.

 


Striding Confidently Before Going Up

 

At that height the curvature of the earth is quite evident.  There was an air-show underway at the airport we took off from and we were soon looking down on the planes of the RAAF  Roulette aerobatic display team.  They looked like little model aircraft flying in perfect formation.  

Read more ...

Opinions and Philosophy

Manufacturing in Australia

Originally written in August 2011 - it might have been yesterday - so little has changed.

 

 

Manufacturing viability is back in the news.

The loss of manufacturing jobs in the steel industry has been a rallying point for unions and employers' groups. The trigger was the announcement of the closure of the No 6 blast furnace at the BlueScope plant at Port Kembla.  This furnace is well into its present campaign and would have eventually required a very costly reline to keep operating.  The company says the loss of export sales does not justify its continued operation. The  remaining No 5 blast furnace underwent a major reline in 2009.  The immediate impact of the closure will be a halving of iron production; and correspondingly of downstream steel manufacture. BlueScope will also close the aging strip-rolling facility at Western Port in Victoria, originally designed to meet the automotive demand in Victoria and South Australia.

800 jobs will go at Port Kembla, 200 at Western Port and another 400 from local contractors.  The other Australian steelmaker OneSteel also recently announced a workforce reduction of 400 jobs.

This announcement has reignited the 20th Century free trade versus protectionist economic and political debate. Labor backbenchers and the Greens want a Parliamentary enquiry. The Prime Minister who reportedly initially agreed has now, perhaps smelling trouble, demurred.

Read more ...

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