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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

South Korea & China

March 2016

 

 

South Korea

 

 

I hadn't written up our trip to South Korea (in March 2016) but Google Pictures gratuitously put an album together from my Cloud library so I was motivated to add a few words and put it up on my Website.  Normally I would use selected images to illustrate observations about a place visited.  This is the other way about, with a lot of images that I may not have otherwise chosen.  It requires you to go to the link below if you want to see pictures. You may find some of the images interesting and want to by-pass others quickly. Your choice. In addition to the album, Google generated a short movie in an 8mm style - complete with dust flecks. You can see this by clicking the last frame, at the bottom of the album.

A few days in Seoul were followed by travels around the country, helpfully illustrated in the album by Google generated maps: a picture is worth a thousand words; ending back in Seoul before spending a few days in China on the way home to OZ. 

Read more ...

Fiction, Recollections & News

The Meaning of Death

 

 

 

 

 

 

'I was recently restored to life after being dead for several hours' 

The truth of this statement depends on the changing and surprisingly imprecise meaning of the word: 'dead'. 

Until the middle of last century a medical person may well have declared me dead.  I was definitely dead by the rules of the day.  I lacked most of the essential 'vital signs' of a living person and the technology that sustained me in their absence was not yet perfected. 

I was no longer breathing; I had no heartbeat; I was limp and unconscious; and I failed to respond to stimuli, like being cut open (as in a post mortem examination) and having my heart sliced into.  Until the middle of the 20th century the next course would have been to call an undertaker; say some comforting words then dispose of my corpse: perhaps at sea if I was travelling (that might be nice); or it in a box in the ground; or by feeding my low-ash coffin into a furnace then collect the dust to deposit or scatter somewhere.

But today we set little store by a pulse or breathing as arbiters of life.  No more listening for a heartbeat or holding a feather to the nose. Now we need to know about the state of the brain and central nervous system.  According to the BMA: '{death} is generally taken to mean the irreversible loss of capacity for consciousness combined with the irreversible loss of capacity to breathe'.  In other words, returning from death depends on the potential of our brain and central nervous system to recover from whatever trauma or disease assails us.

Read more ...

Opinions and Philosophy

Medical fun and games

 

 

 

 

We all die of something.

After 70 it's less likely to be as a result of risky behaviour or suicide and more likely to be heart disease followed by a stroke or cancer. Unfortunately as we age, like a horse in a race coming up from behind, dementia begins to take a larger toll and pulmonary disease sees off many of the remainder. Heart failure is probably the least troublesome choice, if you had one, or suicide.

In 2020 COVID-19 has become a significant killer overseas but in Australia less than a thousand died and the risk from influenza, pneumonia and lower respiratory conditions had also fallen as there was less respiratory infection due to pandemic precautions and increased influenza immunisation. So overall, in Australia in 2020, deaths were below the annual norm.  Yet 2021 will bring a new story and we've already had a new COVID-19 hotspot closing borders again right before Christmas*.

So what will kill me?

Some years back, in October 2016, at the age of 71, my aorta began to show it's age and I dropped into the repair shop where a new heart valve - a pericardial bioprosthesis - was fitted. See The Meaning of Death elsewhere on this website. This has reduced my chances of heart failure so now I need to fear cancer; and later, dimentia.  

More fun and games.

 

Read more ...

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